MEGAPOLI PROJECT FINAL REPORTmegapoli.dmi.dk/publ/MEGAPOLI_FinalReport_Part1.pdf · MEGAPOLI...

MEGAPOLI PROJECT FINAL REPORT – September 2011

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MEGAPOLI PROJECT FINAL REPORT Grant Agreement number: 212520

Project acronym: MEGAPOLI

Project title: Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation

Funding Scheme: Collaborative Project

Period covered: from 1 October 2008 to 30 September 2011

Name of the scientific representative of the project's co-ordinator1, Title and Organisation:

Alexander Baklanov, Prof., Danish Meteorological Institute

Tel: +45-3915-7441

Fax: +45-3915-7400

E-mail: [email protected]

Project website address: http://www.megapoli.info

1 Usually the contact person of the coordinator as specified in Art. 8.1. of the Grant Agreement.


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Content: 1. Final publishable summary report ...................................................................................................3

1.1. Executive Summary ..................................................................................................................3 1.2. Summary Description of Project Context and Objectives ........................................................5 1.3. Description of the Main S&T Results/ Foregrounds ................................................................8 1.4. Potential Impact, Main Dissemination Activities and Exploitation Results...........................37

2. Use and dissemination of foreground ............................................................................................44 2.2. List of Scientific (Peer Reviewed) Publications .....................................................................45 2.2. List of Dissemination Activities .............................................................................................52 2.3. List of Applications for Patents, Trademarks, Registered Designs, etc..................................61

3. Report on societal implications......................................................................................................63


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1. Final publishable summary report

1.1. Executive Summary The challenge For the past few hundred years, human population has been clustering in increasingly large settlements. Urban areas with more than about 5 mln people are usually called megacities. In 2007, the world’s urban population exceeded the rural. At present, there are about 30 cities worldwide with a population exceeding 7 mln inhabitants. These numbers are expected to grow considerably in the near future. In Europe there are several major centers that clearly qualify as megacities: London, Paris, the Rhine-Ruhr and Po Valley regions, Moscow, and Istanbul. MEGAPOLI brought together leading European research groups, state-of-the-art scientific tools and key players from non-European countries to investigate the interactions among megacities, air quality and climate. MEGAPOLI included both basic and applied research, and bridged spatial and temporal scales connecting local emissions, air quality and weather with global atmospheric chemistry and climate. Project objectives The main MEGAPOLI objectives were (i) to assess impacts of megacities and large air-pollution hot-spots on local, regional and global air quality, (ii) to quantify feedbacks among megacity air quality, local and regional climate, and global climate change, (iii) to develop improved integrated tools for prediction of air pollution in megacities. Methodology The project focused on the latter, spanning the range from emissions to air quality, effects on regional and global climate, and feedbacks and mitigation potentials. The project took into account the different features and growing trends that characterize cities located in developed and developing countries to highlight their present and future effects on local to global air quality and climate. Our hypothesis was that megacities around the world have an impact on air quality not only locally, but also regionally and globally and therefore can also influence the climate of our planet. Some of the links of megacities, air quality and climate interactions have already been considered by previous studies and are reasonably well-understood. Better understanding and quantifying of these links and complete quantitative picture of the interactions was the focus of MEGAPOLI. The project addressed, at different levels, practically all major megacities around the globe. Achieved results (i) Integration of the interactions and processes affecting air quality and climate change on different

scales coupled with the capability of estimating the human, ecosystem and economic impact of air pollution resulting from megacities;

(ii) Development of an integrated European methodology and tools to assess the impacts within and from megacities on city to global scales;

(iii)Integration of ground-based, aircraft and satellite technologies with state-of-the-art modelling tools;

(iv) Integrated approaches for addressing the feedbacks and interlinkages between climate change and regional air quality related to megacities;

(v) Integration of knowledge and practical implementation of improved tools according to level of complexity to a range of megacities and hotspots;

(vi) Improved current and future emission estimates for natural and anthropogenic sources of air pollutants;


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(vii) Development of an integrated assessment methodology for supporting EU and global policy frameworks;

(viii) Examination of the important feedbacks among air quality, climate and climate change; (ix) A robust, global information dissemination gateway on air quality, climate change and

mitigation and policy options for European stakeholders strengthening the European research area.


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1.2. Summary Description of Project Context and Objectives The EC FP7 MEGAPOLI (Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation; http://megapoli.info) project brought together leading European research groups, state-of-the-art scientific tools and key players from non-European countries to investigate the interactions among megacities, air quality and climate. MEGAPOLI bridged the spatial and temporal scales that connect local emissions, air quality and weather with global atmospheric chemistry and climate. The main MEGAPOLI objectives were the following:

to assess impacts of megacities and large air-pollution “hot-spots” on local, regional, and global air quality and climate;

to quantify feedbacks between megacity emissions, air quality, local and regional climate, and global climate change;

to develop and implement improved, integrated tools to assess the impacts of air pollution from megacities on regional and global air quality and climate and to evaluate the effectiveness of mitigation option.

In order to achieve these objectives, the main steps in the project were:

• Develop and evaluate integrated methods to improve megacity emission data • Investigate physical and chemical processes starting from the megacity street level,

continuing to the city, regional and global scales • Assess regional and global air quality impacts of megacity plumes • Determine the main mechanisms of regional meteorology/climate forcing due to megacity

plumes • Assess global megacity pollutant forcing on climate • Examine feedback mechanisms including effects of climate change on megacity air quality • Develop integrated tools for prediction of megacity air quality • Evaluate these integrated tools and use them in case studies • Develop a methodology to estimate the impacts of different scenarios of megacity

development on human health and climate change • Propose and assess mitigation options to reduce the impacts of megacity emissions

We followed a pyramid strategy of undertaking detailed measurements in one European major city, Paris, performing detailed analysis for up to 12 megacities with existing air quality datasets and investigating the effects of all megacities on climate. The results are being disseminated to authorities, the policy community, researchers and other stakeholders in the corresponding megacities. MEGAPOLI included both basic and applied research, and bridged the spatial and temporal scales that connect local emissions, air quality and weather conditions with global atmospheric chemistry and climate. In order to fulfil the objectives the following scientific questions were addressed:

Q1: What is the change of exposure of the overall population to the major air pollutants as people move into megacities? What are the health impacts of this exposure? (Objective 1) Q2: How do megacities affect air quality on regional and global scales? What is the range of influence for major air pollutants (ozone, particulate matter, etc.)? (Objective 1)


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Q3: What are the major physical and chemical transformations of air pollutants as they are moving away from megacities? What happens to the organic particulate matter, volatile organic compounds, etc? (Objective 1) Q4: How accurate are the current emission inventories for megacities in Europe and around the world? What are the major gaps? (Objective 1) Q5: How large is the current impact of megacities on regional and global climate? (Objective 2) Q6: How will the growth of megacities affect future climate at global and regional scales? (Objective 2) Q7: What is the impact of large-scale dynamic processes on air pollution from megacities? (Objective 2) Q8: What are the key feedbacks between air quality, local climate and global climate change relevant to megacities? For example, how will climate change affect air quality in megacities? (Objective 2) Q9: How should megacities (emissions, processing inside megacities, meteorology) be parameterised in regional and global models? (Objective 3) Q10: What type of modelling tools should be used for the simulation of multi-scale megacity air quality - climate interactions? (Objective 3) Q11: Which policy options are available to influence the emissions of air pollutants and greenhouse gases in megacities and how can these options be assessed? (Objective 3)

In order to answer the above questions and achieve the main objectives we performed the following tasks:

T1: Develop and evaluate integrated methodologies to improve emission data from megacities on regional through global scales; (Objective 1) T2: Investigate physical and chemical processes starting from the street level in a megacity, continuing to the megacity scale, and then to the regional and global scales; (Objective 1) T3: Assess regional and global impacts of megacity plumes, including: atmospheric transport (local pollution build-up and its regional/global transport) and chemical transformation of gas and aerosol pollutants emitted in megacities; (Objective 1) T4: Quantify impacts of polluted air-masses on larger scale atmospheric dynamics (physics and chemistry, hydrological processes, long-range/hemispheric transport, etc.); (Objective 2) T5: Determine the main mechanisms of regional meteorology/climate forcing due to megacity plumes; (Objective 2) T6: Assess global megacity aerosol/pollutant forcing and its effects on global climate; (Objective 2) T7: Examine feedback mechanisms including effects of climate change on megacity environment and emissions; (Objective 2) T8: Develop improved 'integrated' tools for prediction of air pollution in megacities; (Objective 3) T9: Evaluate these integrated modelling tools and use them in case studies for selected megacities; (Objective 3) T10: Develop and apply a methodology to estimate the impacts of different scenarios of megacity development on human health and climate change; (Objective 3) T11: Propose and assess mitigation options to reduce the impacts of megacity emissions: provide support for European Commission’s new air pollution and climate change strategy and policies. (Objective 3)

The final results and their potential impacts of MEGAPOLI are the following. The project contributed to the strategic goal of promoting sustainable management of the environment and its resources. This has been realised by advancing our knowledge on the


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interactions between air quality, climate and human activities related to large urban centres and hotspots. Megacities constitute major sources of anthropogenic air pollution and hence affect the lives of hundreds of millions of people in the world directly by the quality of air that they breathe and through complex interactions resulting in climate change. Research within the project has led to improved modelling and assessment tools. In particular, MEGAPOLI formulated a European methodology for integrated air quality and climate assessment over multiple scales (urban to global). MEGAPOLI placed particular emphasis on the interactions between air quality and climate change impacts resulting from megacities on regional to global scales and potential mitigation options. It will further lead to an integrated methodology and corresponding tools to assess these impacts not only in Europe, but also elsewhere. MEGAPOLI is leading to significant scientific innovations including:

(i) Integration of the interactions and processes affecting air quality and climate change on regional to global scales coupled with the capability of estimating the human, ecosystem and economic impact of air pollution resulting from megacities;


(iii) Integration of ground-based, aircraft and satellite technologies with state-of-the-art modelling tools;


(v) Integration of knowledge and practical implementation of improved tools according to level of complexity to a range of megacities and hotspots;


(vii) Development of an integrated assessment methodology for supporting EU and global policy frameworks. This will be achieved through the assessment of mitigation options and the quantification of impacts from polluted air-masses on larger scale atmospheric dynamics;

(viii) Examination of the important feedbacks among air quality, climate and climate change; (ix) A robust, global information dissemination gateway on air quality, climate change and

mitigation and policy options for European stakeholders strengthening the European Research Area (ERA).

MEGAPOLI significantly extends the current state-of-the-art in the assessment capabilities within Europe by developing and implementing reliable integrated tools on multiple scales and for multiple pollutants. These have been and will be applied to assess directly the impact of the largest urban centres and hotspots in Europe and globally by employing highly advanced as well as simpler tools. The project brings together current off-line approaches as well as new on-line methods enabling feedbacks to be quantified on multiple scales enabling mitigation options to be examined more effectively. The official website of the MEGAPOLI project is http://megapoli.info. It shows structurally general information on the project, partners and collaborators involved, key megacities in focus studied; description of workpackages, working plans, and contacts. The sections “News and Publications” and “Project Results” were frequently updated with information about recent relevant news, MEGAPOLI newsletters published every 3 months, meetings, presentations, publications, and others.


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1.3. Description of the Main S&T Results/ Foregrounds The main scientific results achieved during the project in the forms of answers on the main science questions (see Section 1.2) are described in this Section and in the Brochure with our Answers on the MEGAPOLI Scientific Questions (see references and web-links below). MEGAPOLI practical recommendations and contribution to the EC air policy review are described in the following Section 1.4.

MEGAPOLI Scientific Questions and Answers Q1: What is the change of exposure of the overall population to the major air pollutants as people move into Megacities? What are the health impacts of this exposure? For the past few hundred years, human populations have been clustering in increasingly large settlements. In 2007, for the first time in history, the world’s urban population exceeded the rural population. At present, there are about 20 cities worldwide with a population of 10 million or greater, and 30 with a population exceeding 7 million. Most of them (especially quickly growing cities) are situated in poor and developing countries and characterized by high air pollution levels. These numbers are expected to grow considerably in the near future. From the year 2000 to 2030 the global urban population percentage is expected to rise from 47% (2.9 billion) to 60% (5 billion). 95% of this growth will be in less developed countries. By 2015, 16 of the world's 24 cities with more than 10 million people will be located in Asia. The urban transition now underway in Asia is taking place on a scale unprecedented in human history. The emissions of air pollutants per capita in Megacities across the world vary widely. For example, the average annual emission of black carbon (often called also soot) varies from 0.4 kg/capita in European Megacities to 1.2 kg/capita in Asian Megacities (Fig. 1.1). The elevated emission levels per capita in the Megacities in Asia and Africa are related to the fuels used for residential heating and cooking.

Figure 1.1. Annual emissions of Black Carbon and NOx per capita in Megacities in different continents.


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The per capita emissions in the European Megacities (Paris and London) studied in MEGAPOLI are a lot lower compared to the per capita emissions in the rest of the same country. As an example, the per capita PM10 residential emissions in London and Paris are more than a factor of 5 lower than in the rest of the UK or France, respectively (Fig. 1.2). This is due to the use of cleaner fuels in these cities due to policy measures (e.g., after the London 1952 smog episode, poor quality coal was banned from the city) and available infrastructure, e.g., natural gas distribution networks in the cities. Per capita residential combustion emissions for Paris are higher than London due to wood use in Paris and the surrounding Ile de France. This example illustrates that emission per capita can be dramatically different but highly detailed local inventories are needed to quantify this. Local inventories for Megacities in other parts of the world are needed to better understand and quantify exposure of their population. Down-scaling of the emissions of the country may result in substantial overestimation of emissions in Megacities.

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0.5

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1.5

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MP_base Down-scaled

Bottom-up MP_base Down-scaled

Bottom-up

UK London London France Paris Paris

Emis

sion

/cap

ita (k

g)

PM10_residential combustion

Figure 1.2. Annual PM10 emissions per capita for residential combustion in London, the UK, Paris and France. Even if emissions per capita may be lower in modern Megacities, the high population density and the corresponding higher emission densities result in higher pollutant concentrations. The population in Megacities is generally exposed to higher levels of air pollution than people living in rural areas. For example, according to the APHEKOM project compliance with the WHO's annual PM2.5 air quality guideline (10 μg m-3) in 25 large European cities could add up to 22 months of life expectancy for persons 30 years of age and older, while producing €31.5 billions in monetary health benefits every year. The research showed that there would be special benefits for children, older people and poorer families, as well as for those who already suffer from respiratory and heart problems. Living near busy roads could be responsible for 15% of asthma cases in children, and for similar or higher percentages of other common chronic respiratory and cardiovascular diseases in adults 65 and over. Additional information can be found in:

• MEGAPOLI Deliverable 4.4 • MEGAPOLI Deliverable 4.5


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Q2: How do Megacities affect air quality on regional and global scales? What is the range of influence for major air pollutants (ozone, particulate matter, etc.)? Megacities represent only a small part of the Earth’s surface (less than 0.2%), but account for approximately 10% of the world’s population. These densely populated regions emit significant amounts of pollution to the atmosphere, and the local effects are especially evident within the boundaries of well-known polluted Megacities, such as Beijing and Delhi, as well as the London and Los Angeles of the past. However, this pollution is not confined to only remaining within the bounds of the Megacities themselves, but can be transported over regional scales, contributing to the pollution levels in other regions, as well as to the hemispheric background pollution. Even if the pollutants can be transported over long distances their concentrations decrease rapidly as they are transported away from Megacities due to dilution and removal. The Megacities’ impacts are quite variable in space and time and are often in directions different than that of the average prevailing winds. The average transport distance (distance from the source area to the center of the pollution plume) for black carbon and other primary fine PM components is around 100 – 200 km for most Megacities examined. On the other hand, the secondary PM species can be transported much further with sulfate and secondary organic aerosol often transported on average over 400 km (Figure 2.1). Maximum transport distances of the main plume are significantly higher, with secondary particulate matter impacts reaching as far as 2000 km away from a Megacity in specific periods (this is a rare event).

Figure 2.1. Average fractional change in predicted (by PMCAMx) PM2.5 concentrations assuming zero anthropogenic emissions in Paris for summer and winter. The impacts of Paris on the concentrations of the primary and secondary pollutants were detectable as far as 200 km from the agglomeration, the maximum distance of the MEGAPOLI research flights. Model simulations show strong build-up of secondary organic aerosol on specific days as the plume moves away from the agglomeration. This build-up starts around noon, due to photochemical processes, and still continues at night due to condensation of material to the particulate phase (Fig. 2.2). In the evening, the plume is 200 km away from Paris, clearly affecting the regional air quality. Although due to the prevailing winds, one might expect a significant impact of pollution from the Boston – New York – Washington region to have a significant influence on the European atmosphere, it turns out that most of this pollution is diluted and is transported over Europe at high altitudes, so that on the whole, especially at the surface, without any significant above average concentration event observed in association with pollution coming from that area. It is also clear that orographic features like mountains can have an impact on the range of the Megacities’ effect on

250 km250 km

Summer Winter

250 km250 km

Summer Winter


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regional air quality, which is seen in the example of the Po Valley, one of the most polluted areas in Europe, which rarely impacts the air quality outside this confined North Italian region. The impacts of Megacities on O3 levels are usually much smaller than on PM and primary pollutants like NOx. Megacities actually tend to cause a decrease of O3 mixing ratios directly in the cities (due to its reaction with NO), while increasing O3 downwind of the cities (by up to 10 ppb).

07h

10h

13h

16h

19h

22h

Figure 2.2: Simulated by CHIMERE urban OA plume on July 16 at different times of the day. Surface OA mass concentrations are given in µg m-3.

Globally the impacts of Megacities on the total burdens of the directly emitted gases are comparable to or slightly smaller than their relative contribution to the global total emissions (several percent), while the impact on global tropospheric O3 is much smaller (< 1%). Interestingly, this impact tends to become even smaller in future scenario simulations, and the ozone chemistry of Megacities tends to become more strongly influenced by upwind pollutant emissions relative to the emissions in the Megacities themselves.


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While the effects of Megacities on regional pollutant concentrations levels are limited in spatial extent, most of the pollutants are still exported over long distances. For example, for Megacities in the middle and high latitudes, such as Eurasia, 17–34% of the mass of pollutants with a lifetime of 10 days is exported beyond 1000 km and still remains in the lowest 1 km above the Earth’s surface. Vertical mixing plays a large role in determining the pollution build-up near the surface, both immediately in and around the Megacity, as well as thousands of km downwind. In the tropics strong upwards transport, but also stronger scavenging of soluble aerosols leads to a smaller range of the impacts of Megacities. For PM2.5 particles about 50% of the emitted mass is transported more than 1000 km away from the source location before being deposited back onto the Earth’s surface. On the other hand, this long-range deposition generally occurs over large areas, making it more dilute, so that the greatest exposure to high aerosol concentrations tends to still be within the bounds of the cities themselves. Megacities in Europe are the most significant contributors to deposition of aerosols in the Arctic (especially absorbing aerosols like soot), regardless of whether considering the annual or only the wintertime deposition. Among these cities the largest contributors are Saint-Petersburg, Moscow and the Ruhr Valley (western Germany). Roughly speaking, one gram of emission of soot in Saint Petersburg results in a deposition in the Arctic which is equivalent to 30 grams emitted in Beijing, 100 grams from Seoul, and 200 grams from Shanghai. This suggests that in order to most effectively reduce soot deposition in the Arctic, the focus needs to be placed on northern Eurasian sources. Additional information can be found in:

• MEGAPOLI Deliverable 5.4 • MEGAPOLI Deliverable 5.6 • Wagstrom K. M. and S. N. Pandis (2011) Source-receptor relationships for fine particulate

matter concentrations, Atmos. Environ., 45, 347-356. Q3: What are the major physical and chemical transformations of air pollutants as they are moving away from Megacities? What happens to the organic particulate matter, volatile organic compounds, etc? A number of important changes to the concentrations of air pollutants take place as they are advected and dispersed away from Megacities. The dominant process affecting concentrations (but not the total mass) is dilution. The dilution rate depends a lot on the meteorological conditions but in general reduces rapidly the concentrations of inert pollutants within 10s of kilometers from the Megacity. During the MEGAPOLI campaign flights around Paris, the Paris plume for BC and the slowly reacting VOCs could however clearly be detected in distances up to 150 km even for relatively windy days (up to 10 m/s). Physical and chemical changes also take place. Physical changes include the evaporation of semi-volatile particulate matter components as the air mass is diluted moving away from the city. Fig. 3.1 shows the reduction of the average ammonium nitrate levels from their peak in the city to less than 10% of their peak concentrations within 50 km from Mexico City. This is due to a combination of dilution, evaporation, and rapid dry deposition of nitric acid. Evaporation of primary organic aerosol also takes place in similar time and length scales. One other important mechanism of physical changes is the urban heat island (UHI) effect on the urban boundary layer height and correspondingly forming the so-called ‘urban plume’ effecting boundary layer characteristics downwind from the city (usually increasing turbulent mixing and BL height, forming of an elevated inversion layer, etc.).


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Figure 3.1: Average fine particulate nitrate concentrations in and around Mexico City during the MILAGRO study [Karydis et al., 2011]. The area shown is 210x210 km.

Chemical changes include the formation of ozone, sulfates, and secondary particulate matter. The chemical intricacies of ozone formation can often lead to the maximum ozone levels being observed downwind of Megacities. The same behaviour can be observed for sulfates. The production of sulfuric acid from sulfur dioxide is relatively slow and therefore the peak sulfate concentrations under a number of meteorological conditions can be observed downwind of their sources. The change in the chemical composition of aerosols is also quite drastic. The evaporation of the semi-volatile (hydrocarbon-like) organic compounds and their subsequent oxidation in the gas phase leading to the production of condensable secondary particulate matter together with the more traditional formation of secondary organic PM (from VOCs like the monoterpenes, aromatics, isoprene, etc) leads to a change of the OA from something that resembles emissions of combustion sources to a very oxygenated mixture of compounds. As a result the organic PM exported by Megacities is quite different chemically from that emitted by the sources inside the city. The aged organic PM is a lot more hygroscopic and less volatile than the original PM. Build-up of secondary pollutants was clearly observed from the Paris research flights crossing the pollution case, in this case heading to the north, several times. Fig. 3.2 shows on the left observed concentrations of secondary pollutants, and on the right simulated ones. Organic aerosol, nitrate, and sulfate clearly show enhanced values within the plume, but the variability with distance is not obvious. Apparently formation of secondary pollutants is counterbalanced by dilution.


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Figure 3.2: Comparisons of Organic Aerosol, nitrate, sulfate, ammonium, BC from measurements (left, with suffix m) and from CHIMERE simulations (right, with suffix v) for the flight on July 16. All values are given

in µg m-3.

Q4: How accurate are the current emission inventories for Megacities in Europe and around the world? What are the major gaps? Emissions inventories are one of the critical links between human activities and their impact on the environment, providing the main input into atmospheric models. In MEGAPOLI, we compared three major, widely-used global emissions inventories to each other and to two locally-developed, city-level inventories. There are many common sources of data between the inventories, as well as similarities in their construction methodologies. Nevertheless, there are some large differences (often a factor of two) between the emissions for individual cities, even when the total global


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emissions are very similar. The geographical distribution of the emissions within countries is particularly important in explaining these differences (more so than differences in the country totals), and there are also sometimes large differences between the contribution of various sectors to the total emissions from each city, which are related to the respective methodologies used in the inventory construction. Compared to the city-specific inventories, the global inventories show various patterns, e.g., underestimating the emissions from the European and Chinese Megacities and overestimating emissions in Los Angeles and in the rest of Asia (except China). Although in most cases the city emissions are similar between the city-specific inventories, there are also sometimes large differences between these specialized inventories, and in many cases the differences between the city-specific emission inventories and the global inventories are similar to the differences between the global inventories themselves. For Europe, during MEGAPOLI local bottom-up inventories for Paris, London, the Rhine-Ruhr area (Germany) and the Po-valley (Italy) were compared to regional European emission inventories. It was shown that the allocation of the emission in the regional down-scaled inventory can deviate substantially from the Megacity bottom-up inventories. For example, the PM10 and NOx in local inventories are respectively 26% and 62% (London), 33% and 95% (Paris), 55% and 108% (Rhine-Ruhr) and 110% and 107 % (Po valley) of the emission allocated to the same area in the regional inventory. The discrepancies for NOx are small, but for PM and VOCs they are major. The agreement for the Po valley appears reasonable but if we zoom in on a city level (Milan) similar problems are seen as in Paris and London. Major discrepancies are caused by the allocation and spatial distribution of emissions. Since the discrepancies are large, predicted concentrations and population exposure may be significantly different. Use of the improved bottom-up emissions improved the abilities of the CTMs used in MEGAPOLI (LOTOS-EUROS, PMCAMx, etc.) to reproduce the observed pollutant concentrations in Paris. Even after the development of bottom-up inventories a number of key questions remain for the European Megacities considered:

• A number of unregulated sources (e.g., cooking) tend to be overlooked as there is less an incentive to know their emissions accurately.

• No local or regional inventory includes resuspension emissions from traffic although it is expected to be an important contributor to concentration levels near busy roads.

• Ratios between pollutants by source sector differ remarkably between local and national scale inventories; even for key sources, e.g. the NOx/PM ratio of road transport emissions. This suggests the use of very different emission factors but this is generally unknown and not documented.

MEGAPOLI demonstrated that it is possible to combine local bottom-up inventories with national and regional inventories to produce a consistent set for air quality modelling and policy assessments. This greatly enhances our potential to evaluate local source contributions and single out issues and targets for policy making. Satellite observations allow top-down estimates of emissions to be made for nitrogen oxides (NOx = NO + NO2), but require poorly quantified a priori information on the NOx lifetime. During MEGAPOLI a method for the simultaneous determination of megacity NOx emissions and lifetimes from satellite measurements was developed by analyzing the downwind patterns of NO2 separately for different wind conditions. Daytime lifetimes are ~4 hours at low and mid-latitudes, but ~8 hours in wintertime for Moscow. The derived NOx emissions are generally in good agreement with existing emission inventories, but are higher by a factor of 3 for the Saudi Arabian capital Riyadh.


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The Megacity emissions analysis shows very distinct characteristics in the main sources of pollutants, depending on the geographical regions where the megacities are located. In Europe and North and South America, land/road transport is generally most important for CO and NOx emissions from the megacities, while in Asia and Africa, megacity CO emissions are dominated by residential biofuel use, while industrial emissions dominate for NOx. For non-methane hydrocarbons, emissions in OECD megacities are mainly caused by industry and traffic, whereas in non-OECD countries residential biofuel use normally makes the most significant contribution. There are a few key gaps in our knowledge that will need to be addressed in follow-up studies to MEGAPOLI. One of these concerns the initial step of developing emissions databases: the assumption about the distribution of emissions according to gridded population density maps, rather than according to the actual location of the various emitting processes. Even when a source is directly linked to population, like residential combustion, we the information about variation in fuels, fuel quality and appliance types between the MC and the remainder of the country is often lacking; yet these factors determine the actual emission Finally, MEGAPOLI studies have pointed to notable differences in per capita emissions from the various megacities. A better understanding of the reasons for these differences is needed to formulate recommendations for how to reduce or minimize the emissions in cities where per capita emission are particularly high. This would also help us to make progress on a final fundamental question: are emissions per capita from an urban person generally higher or lower than from a rural person (which is difficult to answer when emissions for many sectors are simply distributed according to population), how does this vary as a function of the pollutant, sector, affluence, and region of the world, and what differences are there in the impacts of these differences in per capita emissions on health and climate? Thus, MEGAPOLI has shown that more work is needed at the inventory development level to better determine Megacity emissions especially outside Europe and North America. For more information please see:

• MEGAPOLI deliverable report 1.5 • MEGAPOLI deliverable report 1.6 • MEGAPOLI deliverable report 3.7 • Beirle et al. (2011) Megacity emissions and lifetimes of nitrogen oxides probed from space,

Science, 333, 1737-1739.

Q5: How large is the current impact of Megacities on regional and global climate? Megacities have strong so-called urban heat islands (UHI), due to differences in surface properties and waste heat from anthropogenic activity. The effects of UHI can be substantial. Anthropogenic heat fluxes for Megacities can be up to 50-500 W m-2, locally (e.g., in Tokyo) reaching 1600 W m-2. Hence Megacities can be warmer than surrounding rural environments by several degrees Celsius (see e.g. Figure 5.1). This heating obviously impacts the local environment directly, but also affects the regional air circulation. The local and partly regional wind patterns are also affected by an increase in the so-called roughness length due to the Megacity building height and density. High resolution simulations show that the boundary layer height (with is extremely important for air pollution) can be increased due to the UHI up to several hundred meters (this is a considerable effect especially for the nocturnal conditions).


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On regional scale, clearly, the contribution of Megacities to air-quality is high and locally it can achieve order of tens percent in concentrations of pollutants (see Fig. 6.1) like ozone and other products of photochemical processes in summer, or aerosols, mainly in winter due to the stability conditions in mixing layer. Based on one year simulation, this results in the Megacities potential to modify surface temperature eventually up to a few degrees (given theoretical complete emission reduction), actually only in local episodes, moreover mainly due to semi-indirect effects. In reality, this effect will be an order of magnitude weaker and at climate time scales probably even lower. Longer (at least one decade) simulations or ensembles runs can provide more comprehensive information. MEGAPOLI studies investigating the possible impacts of European megacities aerosol emissions on regional climate have been conducted for the 2001-2010 decade considering base year 2005 emissions. Results indicate that regional [typically 10 – 1000 km scale] megacity aerosol radiative forcings can be ten to hundred times larger than at global scale. The balance between aerosol radiative cooling and warming and the net sign of TOA forcing depends strongly on the nature of aerosol mixing varying from one megacity to another with the nature of emissions (e.g. sulfur vs black carbon) and local climatic conditions. Due to aerosol aging processes, aerosol absorption and radiative warming is more intense in the immediate vicinity of megacities compared to surrounding regions. As a result megacity aerosols could enhance locally GHG and urban heat island radiative warming, but they however generally tend to mitigate this warming on the regional to continental scale. Aerosol surface megacity radiative forcing is negative due to incoming shortwave radiation dimming which can be significant at regional scale (up to –[1-5] w.m-2). Over the European domain, radiative forcing patterns show an important spatial and seasonal variability, with maximum regional forcings being observed in the summer as a result of reduced ventilation and aerosol removal by precipitation. Beyond radiative forcing the question of whether megacity aerosols are able to trigger significant change in regional climate patterns was also addressed. Using regional climate models, it is very challenging to quantitatively assess the effect of a European megacities aerosol radiative forcing which still represents perturbation of rather limited intensity at the regional to continental scale. Statistical treatments based on ensembles simulations are required methodologies to produce robust results against model internal variability. Qualitatively, a possible mesoscale climatic response to aerosol forcing not only depend on megacity emission intensity, but also on the climatic context. Regions (e.g. the Po Valley for Europe) where meso-scale gradients are important factors in shaping meteorology and climate (e.g. through convection, sea and slope breezes, etc) are more likely to be sensitive to regional aerosol radiative perturbation compared to region where synoptic circulation dominates. Finally, sensitivity studies showed that modification of local and regional climate through megacity aerosol emission is potentially of less importance than the co-induced land-use perturbation associated to urbanization (compared to a rural state).

Figure 5.1. Difference plots for 2 m temperature (ºC) for Paris metropolitan area between outputs of the urbanized vs. control runs of Enviro-HIRLAM on 21.07.2009 at 6 UTC, Gonzalez et al.


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Figure 5.2. Global distribution of - (left) short-wave, SW all-sky and (right) long-wave, LW clear sky - top-of-atmosphere (TOA) radiative forcing due to aerosols from megacities denoted in W/m2.

For studies of megacity effects on the global climate, using a simple analytical technique based on the climate sensitivity computed by complex models, it was estimated that Megacities contribute due to long-living GHGs emission a warming of over 0.2 K after 100 years, with nearly 90% of this being due to carbon dioxide emissions, and most of the rest due to methane. However, most of this effect would be present even if people did not leave in Megacities but elsewhere in the same country. MEGAPOLI has also examined the impact of pollutants such as NOx, VOC and aerosols that are emitted from Megacities on global climate under present-day conditions (base year 2005). Generally, the contribution of Megacities to global pollutant emissions is of the order of 2% to 6% of the total global annual anthropogenic emission flux (see also the answer to Q2 and Q4). There are four main direct radiative forcing impacts of Megacity emissions (Figure 5.2):

• Ozone production: +5.7±0.02 mW/m2 • Reduction of the methane lifetime due to OH radical production: -2.1±0.13 mW/m2 • Short-wave direct forcing from aerosols: -6.1±0.21 mW/m2 • Long-wave direct forcing from aerosols: +1.5±0.01 mW/m2

The combined effect of all of these individual terms is a rather small negative forcing, that is a cooling, of -1.0±0.32 mW/m2 under present-day conditions. As a result the effect of Megacities on global climate (especially when compared to the same population living elsewhere) is very small. For more information please see:

• MEGAPOLI deliverable report 6.1 • MEGAPOLI deliverable report 6.2 • MEGAPOLI deliverable report 6.3 • MEGAPOLI deliverable report 9.6

Q6: How will the growth of Megacities affect future climate at global and regional scales? Two main types of the mechanisms of growing Megacities on the future climate at global, regional and local scales were considered. Changes to: - Urban features including the urban heat island, land-use, albedo, roughness, moisture, etc. - Emissions of atmospheric pollutants and their subsequent effects feedbacks on climate. The growth of Megacities will considerably affect future urban climate, including increasing urban heat islands (see also Q5), altering the formation and evolution of precipitation, increasing thunderstorm intensity and frequency, etc. For example global climate change (e.g. 2 degrees


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warming) will increase air conditioners use in Megacities. Simulations showed that it can lead to increasing atmospheric temperature in the most populated districts of a Megacity by up to one additional degree.

While the growth of (at least some) Megacities might be expected, the reduction as well as increase of some emissions of anthropogenic origin might occur. Thus, the total effect of the development is not clear. However, in most pollutant concentrations the contribution of the Megacities looks to be consistent and similar across the next decades, especially in winter as seen in Figure 6.1 for ozone and primary organic aerosol. For the estimate of climate effect potential of these changes see Q5.

Figure 6.1: Megacities contribution (assessed by the difference in simulations with reduction of emission by 5% and rescaled linearly to 100%) in winter for ozone (upper panels, ppbv) and primary organic aerosol (bottom panels, µg/m3) under emission scenarios for 2005, 2020, 2030 and 2050 (from the left to the right). On the global scale given the relatively small current signal of Megacity CO2 (around 0.1 W/m2, equivalent to about 0.2 K by the end of the century), its future impact will simply scale approximately linearly with the evolution of the future emissions of CO2 from megacities. The impact of pollutants such as NOx, VOC and aerosols on climate under future conditions (for the base year of 2050) has been analyzed in MEGAPOLI, showing that compared to present-day total forcing of these atmospheric pollutants of -1.0±0.32 mW/m2, the overall forcing reduces substantially, to less than half of the magnitude of present-day conditions (due to the competition of megacity growth with overall urbanization and meso-city growth), and it changes sign, becoming slightly positive at +0.4±0.11 mW/m2; thus, pollutant emissions from megacities are found to have a very small, slightly warming impact on future climate, adding to the somewhat larger warming impact from CO2. Over the European domain, regional climatic simulation including climate change effects (A1B) and emission scenario has also been conducted for the 2040-2051 decade. Result show that, in term of regional radiative forcing, the reduction of emission (result of cleaner technologies) impact is dominant despite climatic conditions more favorable to pollution accumulation (increased temperatures and anticyclonic stagnation conditions). As a result aerosol radiative forcing induced by European megacities slightly decrease in future conditions and according to scenarios produced by MEGAPOLI. Summarizing the possible effects of growing Megacities on climate change on different scales, we can answer that:


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• On the city- and meso-scales definitely both the urban heat island and megacity emissions are significantly modify the urban climate and this processes will be increasing for growing megacities,

• On regional and continental scale: the effect is modest but it can extends up to one thousand kilometres,

• On global scale: the answer probably ‘No’ due to the urban features and pollutant emissions, but there is a small effect due to greenhouse emissions.

• One should note however that the regional and global effect would be similar or larger if the same population did not live in Megacities but in other areas in the same countries.

For more information please see:

• MEGAPOLI deliverable report 6.6 • MEGAPOLI deliverable report 9.6

Q7: What is the impact of large-scale dynamic processes on air pollution from Megacities? Large-scale dynamic processes are important for determining the outflow of air pollution from Megacities. Several of the key aspects of this are discussed in the answer to Q2. Summarizing:

• Strong winds in mid-latitude cyclonic and anti-cyclonic systems, along with suppressed vertical mixing due to weaker convection than in the tropics, result in long-range, near-surface export of pollutants that can be substantial, especially for source locations in the middle and high latitudes, such as Eurasia, for which 17–34% of the mass of tracers with a lifetime of 10 days are exported beyond 1000 km and still remain in the lowest 1 km above the Earth’s surface.

• Large-scale vertical mixing plays a particularly large role in determining the pollution build up near the surface, both immediately in and around the source location, as well as thousands of km downwind; the vertical mixing differs strongly between cities in the tropics (strong upwards transport, but also stronger scavenging of soluble aerosols) and the mid-latitudes (weaker vertical mixing and scavenging).

• Large-scale horizontal advection can be substantial, seen in the amount – on average about 50% – of the emitted tracer mass of sub-μm sized particles transported more than 1000 km away from the source location before being deposited back onto the Earth’s surface (by precipitation, gravitational sedimentation and turbulent impaction).

• The large-scale dispersion of Megacity pollutants can result in impacts on the populations of surrounding regions of a few cities which are as large as or exceed the impacts of the populations within the cities themselves, though for most cities the long-range transport is into the free troposphere (away from the surface), from which precipitation scavenging directly occurs, so that for most cities, the impact on populations outside the cities is less than half as large as the impact on the city populations themselves;

• The large-scale circulation in the Northern Hemisphere results in Megacities in Europe, especially Saint Petersburg, Moscow and the Ruhr Valley, being the most significant contributors to deposition of aerosols (especially absorbing aerosols like soot) in the Arctic;

• The trans-Atlantic circulation around mid-latitude cyclones and anti-cyclones results in recurrent transport of pollution from North America to Europe, with North American influenced air generally accounting for about 20% of the samples, though a significant, distinct impact of the urban agglomeration of the northeastern USA (Boston – New York – Washington area) on the atmospheric chemistry of Europe, as was anticipated might be possible based on various modeling studies and field campaigns before MEGAPOLI, was not


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found to be the case in a statistical analysis of an extensive dataset of observations and model output.

For more information please see:


Q8: What are the key feedbacks between air quality, local climate and global climate change relevant to Megacities? For example, how will climate change affect air quality in Megacities? Figure 8.1 shows the main linkages between megacities, air quality and climate and the main feedbacks, ecosystem, health and weather impact pathways, and mitigation routes which were investigated in MEGAPOLI. The relevant temporal and spatial scales are also depicted.

Figure 8.1: Connections between Megacities, air quality and climate. Direct impact of climate change on air quality in Meacities can be significant due to temperature (BVOC fluxes, wild fires, deposition, O3, CH4, SOA, pSO4, pNO3), radiation (photolysis), clouds and precipitation change. As climate changes ozone concentrations will further increase, if no emission reduction measures take place. However, the expected emissions reduction during the next several decades is much stronger than the ozone increase due to climate change expected in the most megacities regions studied within the project. Only a more frequent appearance of extremes like heat waves under the climate change might bring air quality problems with e.g. exceedances of limits of ozone concentrations on local or regional scales. The global climate change will also affect on the megacity climate, UHI and urban-induced weather, however it could be different in different climate zones around the world. In general the diurnal temperature range as well as UHI of megacities may amplify as a result of climate change. However, for coastal Megacities climate change-induced increases in land temperature can lead to an increase


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in the temperature gradient between land and sea resulting in more intensive and frequent sea breeze events and associated cooler air and fog. Potential impacts of urban aerosol feedbacks include:

• a reduction of downward solar radiation (direct effect); • changes in surface temperature, wind speed, relative humidity, and atmospheric stability

(semi-direct effect); • a decrease in cloud drop size and an increase in drop number by serving as cloud

condensation nuclei (first indirect effect); • an increase in liquid water content, cloud cover, and lifetime of low level clouds, and

suppression or enhancement of precipitation (second indirect effect). The urban effects of Megacities together with the direct and indirect aerosol feedbacks constitute an important aspect of the multiple interactions between urban air quality and climate. The aerosol indirect effects can lead to changes in daytime temperatures and PBL height, while pollutant concentrations are moderately affected (Figure 8.4). The radiative forcing associated with the aerosol direct effect has a significant impact on average surface temperature and wind speed, as well as on the development of a lower inversion layer. Compared to the direct and indirect aerosol feedbacks, urban feedbacks exhibit the same order of magnitude effects on mixing height, but with strong sensitivity of chemistry and a strong non-linearity. On the local and meso-scale, an observable Megacity effect on meteorology is expected to occur, both via the influence of the Urban Heat Island (UHI) and the city plume. On the regional scale such effects can also be expected since the urban plume can extend up to a few hundred kilometers (Fig. 8.3). On the global scale, the effect of UHI is expected to be negligible.

(a) (b) (c) Figure 8.2: Comparison timeseries of (a) temperature, (b) wind speed, and (c) PM10 concentrations calculated by taking into account (“coupled”) or without (“baseline”) the direct aerosol effect.

(a) (b) (c)

Figure 8.3. Difference maps demonstrating the modeled influence of the aerosol direct effect on (a) wind speed, (b) turbulent kinetic energy and (c) temperature, for the greater Paris area.


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The direct aerosol effect on mesoscale meteorological and dispersion fields over the urban area of Paris, France has been studied by modelling the response of the primary meteorological variables governing the transport and dispersion of pollutants, as well as trends in particulate matter concentrations.

The impact of the direct aerosol effect was found to be substantial with regard the turbulent characteristics of the flow near the surface. Nevertheless, the performance of the modelling tools in predicting urban meteorology and air quality in the specific case was only improved marginally (Figures 8.2 and 8.3), in this way suggesting a stronger influence of the indirect and higher-order aerosol effects that the particular models did not take into account.

Simulations of indirect effects of urban plume aerosols on meteorological fields showed that aerosol feedbacks through the second indirect effect induce considerable changes in meteorological fields and large changes in chemical composition, in particular NO2, in a case of convective cloud cover and little precipitation. However, monthly averaged changes in surface temperature due to aerosol indirect effects of aerosol emissions in Western Europe on surface temperature are about 0.5°C. It also shows that modifications of cloud properties due to anthropogenic aerosols (Figure 8.4) may take place through modification of cloud reflectance and precipitation development, referred to as the first and second aerosol indirect effects respectively. In particular the indirect effects led to stronger convection and heavier precipitation in some places and suppression of precipitation in other places.

Given the very small global climate impact of the air quality effects of Megacities it is expected that any feedbacks on global climate will be very small. On regional scale the effect of Megacities on air-quality is high and locally in vicinity of Megacities studied it can achieve a contribution of a few tens percent in concentrations of pollutants like ozone (mainly in summer) or some aerosols (especially in winter). This suggests the Megacities potential to contribute eventually up to a few degrees (given theoretical complete emission reduction) in surface temperature, but rather locally in space and time, mainly due to semi-direct and indirect effects. This effect will be in order of magnitude weaker at climate time scales. It should be mentioned that these conclusions come from one year simulation only, longer (at least one decade) simulations or ensembles runs can provide more comprehensive information. For more information please see:

• MEGAPOLI deliverable report 4.3 • MEGAPOLI deliverable report 4.1 • MEGAPOLI deliverable report 6.2

Figure 8.4: Indirect aerosol effects by EnviroHIRLAM: Monthly averaged CCN number concentration (x107 m-3) at 850 hPa, Korsholm et al


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Com

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Number of Parameters

Com

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Number of Parameters

Parameters difficult to get?

Too expensive to run?

Globally moreapplicable?

Parameters difficult to get?Parameters difficult to get?

Too expensive to run?Too expensive to run?

Globally moreapplicable?Globally moreapplicable?

Urban Modules

LocalStreet DistrictStreet District

SM2-U

BEP

MRF-UrbanMOSES

PALM

AHF+R+A

UrbanCity/ MegacityCity/ Megacity

RegionalMegacity/ Large Metropolitan AreaMegacity/ Large Metropolitan Area

GlobalClimate-Meso-LES-

=0.1km 10-15km 25-50km3-5km1-3km0.1-1km

Computational time (1 urban grid cell)Computational time (1 urban grid cell)

TEB

Q9: How should Megacities (emissions, processing inside Megacities, meteorology) be parameterised in regional and global models? The main Megacity effects on the urban environment and surrounding atmosphere to be parameterized include:

• urban pollutants emission, chemical transformation and transport, • land-use change due to urbanisation, • anthropogenic heat fluxes, urban heat island, • local-scale inhomogeneties, sharp changes of roughness and heat fluxes, • wind velocity reduction due to buildings, • redistribution of eddies due to buildings, from large to small, • trapping of radiation in street canyons, • effect of urban soil structure, diffusivities heat and water vapour, • internal urban boundary layers and urban mixing height, • effects of pollutants (aerosols) on urban meteorology and climate, • urban effects on clouds, precipitation and thunderstorms.

Atmospheric Chemical Transport Models (CTMs) have different requirements in terms of the way in which they represent urbanization (e.g., different importance of the details of the lower atmosphere structure) depending on the scale of the models (e.g., global, regional, city, local, micro) and the functional type of the model. Incorporation of the urban effects into urban- and regional-scale models of atmospheric pollution should be carried out, first via improvements in the accuracy of meteorological parameters (velocity, temperature, turbulence, humidity, cloud water, precipitation) over urban areas. This requires a kind of “urbanization” of meteorological, numerical weather prediction (NWP) and climate models that are used as drivers for CTMs or special urban met-pre-processors to improve non-urbanized NWP input data. In MEGAPOLI a hierarchy of urban canopy models/parameterisations for different type and scale models was developed (Figure 9.1).

Figure 9.1: MEGAPOLI suggested hierarchy of urban canopy models/parameterisations for different type and scale models. In comparison with NWP models, the urbanization of CTMs has specific requirements, e.g., better resolution of the urban boundary layer vertical structure; by themselves, the correct surface fluxes over the urban canopy are insufficient for CTM runs. Furthermore, for urban air pollution, from traffic emissions and for the modelling of preparedness for emergencies, there is a much greater need for vertical profiles of the main meteorological parameters and the turbulence characteristics within the urban canopy. Other important characteristics for pollutant turbulent mixing in Megacity modelling include the mixing height, which has a strong specificity and heterogeneity over urban areas because of the


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urban heat island, internal boundary layers, and blending heights from different urban roughness neighbourhoods. For the modelling of preparedness for emergencies at local scale (e.g., biological, chemical, or nuclear accidental releases or terrorist acts) the statistical description of building structure is suitable only for distances longer than three or four buildings from the release, whereas for the first two to four buildings from the source, more precise obstacle-resolved approaches are needed. Other specific effects of urban features on air pollution in urban areas, which cannot be realized via the urbanization of NWP models, include:

1. Deposition of pollutants on specific urban surfaces, e.g., on vertical walls, from different building materials and structure, vegetation, etc.

2. Specific chemical transformations, including increasing the residence times of chemical species (e.g., inside street canyons), the heterogeneity of solar radiation (e.g., street canyon shadows) for photochemical reactions, and specific aerosol dynamics in street canyons (e.g., from the resuspension processes).

3. Very heterogeneous emission of pollutants at the sub grid scale, especially from traffic emissions, which need to be simulated on detailed urban road structures with taking into account the distribution of transport flows, etc.

4. The indoor–outdoor interaction of pollutants (not only via heat fluxes), which requires a more comprehensive description and modelling of emissions.

Current types of urban canopy schemes available for model implementation have been reviewed in the context of their application requirements. Given different modeling objectives, there are several types schemes and associated atmospheric models available. They can be separated into three primary categories such as single-layer and slab/bulk-type urban canopy schemes, multilayer schemes, and obstacle-resolved micro-scale models. The first two categories are sufficiently simple (in their grid-averaged representation of urban morphological features as parameters) to be coupled into classical numerical atmospheric models. The third corresponds to computational fluid dynamic-type explicit building-scale resolved models.

Figure 9.2. Anthropogenic heat scaling for use in different resolution models on example of London (Lindberg, Grimmond, Kotthaus, Allen in preparation)


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A large number of urban surface energy balance models now exist with different assumptions about the important features of the surface (e.g., AHF, see Figure 9.2) and exchange processes that need to be incorporated. An extensive international comparison of 33 models has been performed in an effort to understand the complexity required to model energy and water exchanges in urban areas. Some classes of models perform better for individual fluxes but no model performs best or worst for all fluxes. In general, the simpler models perform as well as the more complex models based on all statistical measures. Generally the schemes have best overall capability to model net all wave radiation and least capability to model latent heat flux. Beyond the parameterization from local to regional model scales, it is also important to consider the relationship between regional and global scales. Comparison of global high resolution runs (~40 km) with typical climate resolution runs (175 km) show that the high resolution models are much better at representing the diurnal cycle and probability distribution of ozone concentration in specific Megacities (e.g., London and Paris), with the better representation of emissions in the 40 km model playing a key part in its improved performance. For more information please see:

• MEGAPOLI deliverable report 2.2 • MEGAPOLI deliverable report 2.3 • MEGAPOLI deliverable report 2.7 • MEGAPOLI deliverable report 4.1 • MEGAPOLI deliverable report 4.2

Q10: What type of modelling tools should be used for the simulation of multi-scale Megacity air quality - climate interactions? Processes involving nonlinear interactions and feedbacks between emissions, chemistry and meteorology require coherent and robust modelling approaches. This is particularly important where multiple spatial and temporal scales are involved with a complex mixture of pollutants from large sources, as in the case of Megacities. Numerical weather and air pollution prediction models are now able to approach urban-scale resolution, as detailed input data are becoming more often available. MEGAPOLI suggested a comprehensive integrated modelling framework which was tested for a range of Megacities within Europe and across the world to increase our understanding of how large urban areas and other hotspots affect air quality and climate on multiple scales. The integration strategy in MEGAPOLI was not focused on any particular meteorological and/or air pollution modelling system. The approach considered an open integrated framework with flexible architecture and with a possibility of incorporating different meteorological and chemical transport models. Baklanov (2010) has explained the levels of integration and orders of complexity (temporal and spatial scales and ways of integration) considered in MEGAPOLI:

• Level 1 – Spatial: One-way (Global to regional to urban to street); Models: All. • Level 2 – Spatial: Two-way (Global from and to regional from and to urban); Models: UM-

WRF-CMAQ, SILAM, M-SYS, FARM. • Level 3 – Time integration: Time-scale and direction; Direct and Inverse modelling.

o Order A – off-line coupling, meteorology / emissions to chemistry; Models: All. o Order B – partly online coupling, meteorology to chemistry and emissions; Models:

UKCA, DMAT, M-SYS, UM-WRF-Chem, SILAM. o Order C – fully online integrated with two-way feedbacks, meteorology from and to

chemistry and emissions; Models: UKCA, WRF-Chem, Enviro-HIRLAM, EMAC


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(former ECHAM5/MESSy). A multi-scale modelling framework for global to street scale includes nesting of the land-use characteristics and scenarios, anthropogenic heat fluxes, emission inventories and scenarios, and the representation of atmospheric processes using two-way nesting, zooming, nudging, parameterizations and urban increment methodology. The new or improved interfaces for coupling (direct links between emissions, chemistry and meteorology at every time step) can be implemented or developed and common formats for data exchange can be defined to ease the implementation and to help combine the different models via conventional data exchange protocols. The current chemistry schemes were examined for their suitability to simulate the impact of complex emissions from megacities. The coupled model systems were applied to different European megacities during the project. The framework is used and demonstrated for selected models including UKCA (MetO), WRF-CMAQ (UH-CAIR), PMCAMx (FORTH), Enviro-HIRLAM (DMI), STEM/FARM (ARIANET), M-SYS (UHam) and EMAC (MPIC) on different scales. This part of the studies was linked also to the requirements and use of simpler tools for assessing air quality impacts within megacities (OSCAR - UH-CAIR, AIRQUIS - NILU, URBIS - TNO, EcoSence - UStutt). The focus on integrated systems is timely, since recent research has shown that meteorology/climate and chemistry feedbacks are important in the context of many research areas and applications, including numerical weather forecasting, climate modelling, air quality forecasting, climate change, and Earth system modelling. The prediction and simulation of the coupled evolution of atmospheric transport and chemistry will remain one of the most challenging tasks in environmental modelling over the next decades. Many of the current environmental challenges in weather, climate, and air quality involve strongly coupled systems. It is well accepted that weather is of decisive importance for air quality, or for the aerial transport of hazardous materials. It is also recognized that chemical species will influence the weather by changing the atmospheric radiation budget as well as through cloud formation. Until recently however, because of the complexity and the lack of appropriate computer power, air chemistry and weather forecasts have developed as separate disciplines, leading to the development of separate modelling systems that are only loosely coupled (offline). In NWP, the dramatic increase in computer power enables us to use higher resolution to explicitly resolve fronts, convective systems, local wind systems, and clouds, or to increase the complexity of the numerical models. Additionally we can now directly couple air quality forecast models with numerical weather prediction models to produce a unified modelling system – online – that allows two-way interactions. While climate modelling centres have gone to an Earth System Modelling approach that includes atmospheric chemistry and oceans, NWP centres as well as entities responsible for Air Quality forecasting are only beginning to discuss whether an online approach is important enough to justify the extra cost. NWP and AQ forecasting centres may have to invest in additional computer power as well as additional man power, since additional expertise may be required. We are in favour of integrating weather and chemistry together, for both NWP and air quality and chemical composition forecasting. For NWP centers, an additional attractiveness of the online approach is its possible usefulness for meteorological data assimilation (Hollingsworth et al., 2008), where the retrieval of satellite data and direct assimilation of radiances will likely improve – assuming that the modelling system can beat climatology when forecasting concentrations of aerosols and radiatively active gases. The application of integrated modelling systems for the megacity air quality modelling was implemented for different megacities in Europe as we all other cities (Schlunzen, 2011). In MEGAPOLI (Francis, et al., 2011) describes a number of different integrated modelling systems


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applied to assess the impact of air quality of European and other megacities. These include RAMS-FARM, WRF-Chem, WRF-CMAQ, LOTOS-EUROS, M_SYS-METRAS-MECTM, MEMO-MARS, GRE-CAPS, Enviro-HIRLAM, MESO-NH, and ENSEMBLE. Examples of the use of integrated modelling systems over the European megacities (London, Paris, Po-Valley, and Rhine-Ruhr) and other cities (Lithuania, St. Petersburg metropolitan area-Russia) have been discussed. WRF-CMAQ simulations over London under estimated the PM measurements from air quality stations. There are a number of reasons that may explain this disagreement. These include the underestimation of certain PM emissions, such as coarse dust fractions and non-exhaust sources in the emission inventories. The sensitivity of PM2.5 and PM10 to boundary conditions used in the regional simulation could also provide insight to the model underestimation. LOTUS- EUROS, MEMO-MARS, WRF-CMAQ, PMCAMx, and MESO-NH modelling system have been applied to study the air quality over Paris. The results from LOTUS-EUROS suggested that the model simulation around the Paris area clearly benefit from emission inventories based on nesting information from local inventories for the simulation of particulate matter. However, the average concentrations of PM predicted by LOTUS-EUROS over Paris are much lower compared to available measurements. Simulations with ‘nested’ emissions represented better diurnal cycles for PM when compared with observations. The online coupled modelling system MEMO-MARS has been used to study the feedbacks of direct aerosol effect on PM10 simulations over Paris. The difference field was produced by removing the control simulations from the online results. PM10 concentrations revealed a clear increase over almost the entire domain, reaching up to 2.5 μg m-3 in the central Paris area and the southern part of the computational domain, where higher pollution loads occur due to the prevailing wind flow during the simulation period. This study indicates that feedback processes can be significant for air quality assessment and should form the basis of future studies. Similarly, PMCAMx has been employed to predict concentrations of PM and ozone during July 2009 and winter of 2010. The use of the volatility basis approach in PMCAMx has resulted in significant improvements in the ability to reproduce organic aerosol levels over Paris. MESO-NH has been used to predict primary and secondary aerosols components over Paris region. Analysis of air quality over the Po valley with RAMS-FARM modelling system has shown that the large urbanised areas contribute significantly to regional levels of pollutants such as PM2.5. The study also showed that the Po valley footprint, under prevailing anti-cyclonic circulation conditions, can extend well beyond the immediate region and can affect southern parts of continental Europe and northern Italy. On urban scales, a study with Enviro-HIRLAM for Vilnius has indicated that modifications of the surface parameters can have significant impact on meteorological fields that affect air pollution. For example, it was found that the air temperature at 2 m height is typically higher in modified simulation runs. As an extension of this study, the effect of modified roughness, anthropogenic heat fluxes and the albedo (urbanization) in Enviro-HIRLAM modelling system has been studied for St. Petersburg (Russia). Results showed that for winter the differences between control vs. urbanized runs over the metropolitan area and surroundings were the following: wind at 10 m up to 2 m/s (with a maximum up to 2.9 m/s, at nighttime) and air temperature at 2 m is more than 1ºC (with a maximum up to 2.7oC, at nighttime). The air quality over other non-European megacities like Mexico (PMCAMx and extended version of WRF-Chem), New York (PMCAMx), Phoenix (MM5-CMAQ), Shanghai (WRF-Chem and WRF-CMAQ) and New Delhi (SAFAR) has been also studied. The regional CTMs PMCAMx and an extended version of WRF-Chem have also been used successfully to Mexico City for the periods of April 2003 and March 2006. As mentioned earlier summer levels of PM10 are underestimated as was observed for Shanghai and European cities. An example of air quality forecast (SAFAR) for New


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Delhi has been provided and was found to be within 10% to 20% confidence limit of observations. The forecast model was also able to resolve the diurnal pattern. For this case study sensitivity tests revealed that windblown dust from paved and unpaved roads and construction activities are major contributors to PM and on occasion can be more than the levels due to fossil fuel combustion from transport sector. Although these examples show successful application of integrated models to investigate air quality affecting megacities, a number of research developments are required. These include greater consistency in the use of data for megacities, moving towards online or coupled approaches and the need for dedicated and targeted data sets for model evaluation purposes. Prediction of PM remains a challenge for several models and is an important area for continued research. For more information please see:

• MEGAPOLI deliverable report 7.1 • MEGAPOLI deliverable report 7.2 • MEGAPOLI deliverable report 7.3

Q11: Which policy options are available to influence the emissions of air pollutants and greenhouse gases in megacities and how can these options be assessed? The policy options for mitigating emissions of air pollutants and greenhouse gases have been developed in the MEGAPOLI project for the first level MCs as shown in the following tables.

Table 11.1: Road transport abatement measures descriptions # Measure Short description RT 1 Enhanced use of bicycles

in cities Shift from passenger cars to bicycles in cities. It is assumed that 10% of those car trips could be shifted to bicycling.

RT 2 Enhanced use of public traffic

Shift from passenger cars to public traffic. The aim is to make public transport more attractive. This includes to open up new routes and to improve the quality of the connections (low waiting and transfer times) and to improve the vehicle comfort

RT 3 Promotion of low emission vehicles (E-cars, hybrid vehicles)

One strategy to improve the air quality in cities is to promote low emission vehicles (hybrid and electric cars)

RT 4 Traffic management (Green Wave, improvement of the operation of signalized intersections)

Traffic management, such as Green wave, is an system in which a series of traffic lights are coordinated to allow continuous traffic flow over several intersections on a main road.

RT 5 Low emissions zones Low emission zone is a geographically defined area, which seeks to restrict or prohibit access by specific polluting vehicles or only allow access for low or zero emission vehicles.

RT 6 City toll To overcome the burden caused by traffic, the city of London introduced its congestion charging zone in 2003. Drivers entering the zone have to pay a fee.

RT 7 Increase in fuel costs Costs for fuelling can be an important aspect to influence the driving behavior. An increase in fuel prices (e.g. by raising the fuel taxes) can be an instrument to decrease the amount of kilometres travelled in private transport.

RT 8 Passenger car toll A national toll for passenger cars (as in the Netherlands) can


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support the reduction of vehicle mileage. A differentiation in toll prices depending on the time of the day and the road type and section can additionally help to relieve densely trafficked roads.

RT 9 Use of biofuels The EU Directive 2009/28/EC (Renewable Energy Directive) (successor to Directive 2003/30/EC) describes and regulates the use of biofuels in Europe. An incorporation rate of 10% to fossil fuels by 2020 is to be made. This measure will have a higher incorporation rate to fossil fuels.

The Reduction Potentials are given related to sectoral emissions, in this case related to European (EU 29) road transport emissions. The measure with the highest abatement potential for 1st level Megacities is the measure: “Enhanced use of public traffic”. There you have a PM abatement potential of 60%, CO abatement potential of 51% related to sectoral emissions in 2030. This corresponds to a PM abatement potential of 1%, CO abatement potential of 1.8% related to total emissions in 2030. The measure with the highest abatement potential for the whole European domain is: “Promotion of low emission vehicles (E-cars, hybrid vehicles)”. With this measure impacts a PM abatement potential of 6.8% and a CO2 abatement potential of 17.1% related to sectoral emissions in 2030, corresponding to a PM abatement potential of 0,7% and a CO2 abatement potential of 4,5% related to total emissions in 2030.

Table 11.2: Off-road transport short description

# Measure Short description OT 1 Differentiation of track access

charges for rail transport Destinction of track access charges for rail transport on the emission standards leads to an accelerated introduction of new technologies and reduces the specific NOx emissions from diesel-powered rail transport. The long life of locomotives (in average 32 years) affects new technologies in a fleet with a high delay. Furthermore, it can lead to an increase in the share of electric traction.

OT 2 Further development of emission limits in inland waterway transport

The emission limit II leads to significant reductions in NOx, CO, HC and PM emissions for inland water vessels. More stringent emission limits (e.g. emission limit III) can help to further reduce tailpipe emissions in the whole fleet.

OT 3 Kerosene tax for aviation Likewise to other transport modes, damages to health and environment caused by aviation are so far not internalized. A kerosene tax could help to internalize some of those damages.

OT 4 Low emission zones for construction equipment

In analogy to the low emission zones for on-road vehicles, this policy targets high emitting diesel fuelled construction machinery. Those would be banned from the city if they are not retrofitted with a particulate filter or even replaced by machines with a higher emission standard. The emission standard IIIb, valid from 2012 on, will lead to a 90% reduction compared to level II. The abatement potential is thus higher the sooner this measure is implemented.

The measure with the highest abatement potential for off-road transport is the measure: “Kerosene tax for aviation”. This measure has a CO2 abatement potential of 18% related to sectoral emissions in 2030. The CO2 abatement potential related to total emissions is 1.9% in 2030.


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Table 11.3: Abatement measures for large combustion plants (LCP)

# Measure Short description

LCP 001

Modernisation of the existing coal-fired Large combustion plants

The large number of coal-fired power plants in Europe were built in the 60 years and don’t represent the state of the art. The average efficiencies of the current power plant parks system are about 36%. In the modern hard coal plants can archive the efficiency rates of about 46%, the lignite-fired installations of about 43%. The further development of combustion technologies will allow the efficiency rates higher than 50%. In the IGCC (integrated gasification combined cycle) plants without CCS (Carbon capture and storage) is possible to archive the efficiency rates of about 55%. By application of CCS technology the plant efficiency decrease up to 10%.

LCP 002

Expansion of electricity generation from renewable resources in LCP

In order to prevent the negative impacts of climate change, the EU has set several targets aiming at the reduction of greenhouse gas (GHG) emissions, an intensified use of renewable energy and an increase of energy efficiency. The underlying goal is to keep global warming below 2°C. In order to achieve the 2°C targets renewable energies for electricity generation play an extraordinary role for achieving the climate target. Compared to the Reference scenario the electricity production from renewable energies increases to a maximum of about 1800 TWh in 2050, reaching a share of 45 % of gross electricity consumption in 2050.Wind energy ramps up to 400 TWh in 2020 and further on to 900 TWh in 2050 with an offshore share of about 50 % in 2050. But also electricity from solar photovoltaic and solar thermal power plants contribute with 8 % (260 TWh) in 2050 to total electricity generation.

The Reduction Potentials are given related to sectoral emissions, in this case related to European (EU 29) emissions from Public Electricity and Heat Production. By implementation of Measure LCP 001 mainly NOx, SO2 and particle emissions will be reduced. The measure LCP 002 reduces in particular the CO2 emissions.

Table 11.4: Abatement measures for Small combustion plants (SCP)

# Name Short description

SCP 001

Replacement of solid fuels fired small combustion plants with efficient combustion techniques

Generally, the solid fuels (coal, biomass) fired small combustion plants cause higher specific emissions of incomplete combustion (e.g. particulate matter (PM), CO, VOC) compared to the gas or oil combustion plants. The high emissions are result of inefficient combustion techniques especially of older installations. The significantly emission reduction of PM, CO and VOC can be archived by replacing of old inefficient installation with new biomass fired small combustion plants (e.g. wood pellet boilers, automatic wood boilers) or with gas installations.

SCP 002

Replacement of old gas/oil boilers with modern condensing

The modern condensing boilers have the thermal efficiency up to 98%; compared with conventional boilers 30% higher energy yield can be archived


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# Name Short description boilers

SCP 003

energy-efficient modernisation of old buildings

“Insulation is the most effective way to improve the energy efficiency of the buildings. Insulation of the building envelope helps keep heat in during the winter, but let heat out during summer to improve comfort and save energy. Insulating a home can save 45–55% of heating and cooling energy”. By the energy-efficient modernisation of old buildings about 100 kWh/m²/a can be saved

SCP 004

Switch to renewable heat supply in residential sector

In order to prevent the negative impacts of climate change, the EU has set several targets aiming at the reduction of greenhouse gas (GHG) emissions, an intensified use of renewable energy and an increase of energy efficiency. The underlying goal is to keep global warming below 2°C.

SCP 005 Expansion of district heating network

The district heat has its largest distribution in metropolitan areas and contributes significantly to reducing emissions. By use of district heat about 50% of primary energy saving is possible. The current share of the district heat supply in Germany is about 12%, in France and Norway by about 5%. Poland, Iceland and Lettland have a highest share on district heat supply (more than 50%). This would mean a substantial expansion potential in Europe .

The measures SCP 001-SCP 004 have impact to the whole European Domain. The measure SCP 005 is relevant only for Megacities. The measure ” Expansion of district heating network”( SCP 005) reduces particularly PM10, PM25, CO, NMVOC, which are mostly caused by incomplete combustion. An overview on megacity policies and measures for industrial processes is given in Table 11.5.

Table 11.5: Abatement measures for Industrial Processes


IND 001

Combined climate protection measures in cement industry

The overall output of thermal CO2 can be reduced (“CO2 neutrality”) with the substitution of fossil fuels by (renewable) alternative fuels. In a cement plant with an annual production of 1 million tons of clinker, a thermal substitution rate of 40% reduces the net CO2 generation by about 100,000 t. Regarding the Power generation, cement kilns can contribute with appropriate waste heat utilization to the supply of thermal/electrical power thus saving natural resources and reducing CO2 emissions. The use of waste instead of fossil fuel may reduce CO2 emissions by 0.1 to 0.5 kg/kg cement (varying from 20 to 40%). On average blended cements may reduce carbon emissions from 0.81 kg to 0.64 kg per kg cement (20%). An end-of-pipe technology to reduce carbon emissions may be CO2 removal. Probably the main technique is combustion under oxygen while recycling CO2. However, considerably research is required to all unknown aspects of this technique. Summing up, the use of raw materials, alternative fuels and mineral additions are relevant for the reduction of greenhouse gases. Reducing CO2 emissions it is possible to reduce in the same time emissions like NOx, SOx, NMVOC and PM.


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IND 002

Iron making – Blast furnace - Injection of pulverized coal (PCI)

The steel industry is the second largest energy consumer of all producing sectors. Iron making is the most energy-intensive step in integrated steel making. One of the main energy efficiency measures is the injection of fuels into the blast furnace, especially the injection of pulverized coal. Pulverized coal injection replaces the use of coke, reducing in the same time coke production and hence saving energy consumed in coke making (above) and reducing emissions of coke ovens and associated maintenance costs.

IND 003 Sinter plant – Heat recovery

A possibility to improve the efficiency of sinter making is the heat recovery at the sinter plant. The recovered heat can be used to preheat the combustion air for the burners and to generate high pressure steam. This can be used in steam turbines to generate electricity. Existing plants can be retrofit and there are various systems t for new sinter plants (e.g. Lurgi EOS process).Fuel savings were estimated, based on a retrofitted facility in The Netherlands, to be 0.47 MMBtu/t (0.55 GJ/t) of sinter. The increased electricity generation was estimated to be 1.4 kilowatt hour per ton (kWh/ton) (0.0056 GJ/t) of sinter. The payback time was estimated as 2.8 years. Emissions NOx, SOx and PM are expected to be reduced using this system.

IND 004 Coking plant – Coke dry quenching

Dry quenching of the coke, in place of wet quenching, can be used to recover heat that would otherwise be lost from the coke while reducing dust. Dry coke quenching is typically implemented as an environmental control technology. Various systems are used in Germany, Brazil, Finland, Japan, and Taiwan. All essentially recover the heat in a vessel where the coke is quenched with an inert gas (nitrogen).The steam recovery rate with this equipment is about 0.5 MMBtu/t (0.55 GJ/t) coke. In addition, Nippon Steel's performance record shows that the use of coke manufactured by dry quenching reduces the amount of coke consumption in the blast furnace by 0.24 MMBtu/ton (0.28 GJ/t) molten iron. NOx, SOx and particulate emissions are also reduced with this system [.

The measure IND001 “Combined climate protection measures in cement industry” has the largest mitigation potentials for GHG as well as for AP. The assessment of the health impacts (benefits) of mitigation measures follows the ‘full chain’ or ‘impact pathway’ approach (www.integrated-assessment.eu ; www.externe.info) shown in Figure 11.1.


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Figure 11.1: The Full chain approach of integrated assessment modeling. First a reference scenario is constructed that describes activities and emissions for the considered future year (2030 or 2050) without additional mitigation measures. Then the simulated implementation of the identified measures leads to measure based emission scenarios with reduced emissions. In a next step, for all scenarios (reference and measure based) the concentration of several pollutants (PM10, PM2.5, Ozone, NO2, etc.) is calculated throughout Europe using an atmospheric model. The increase in concentration in cities, and here especially in the 1st level Megacities London, Paris, Rhine-Ruhr area and Po valley is taken into account by applying a new method to estimate the urban increment to be added to the regional concentrations (Torras Ortiz 2010). Measures which have only impact to the 1st level MCs have been distinguished from measures which have impacts to the overall European domain. Concentration-response–functions developed within the EC project HEIMTSA by carrying out a meta-analysis of various epidemiological studies are then applied to convert the concentration together with the population density into health impacts (e.g. years of life lost, cases of chronic bronchitis, respiratory hospital admissions and many others). The health endpoints are then aggregated to DALYs (disability adjusted life years). In order to be able to compare health endpoints with costs within a cost-benefit analysis, health impacts have to be converted into monetary values. This is done by determining stated or revealed preferences of the affected population. One of the methods to estimate these monetary values is to ask for the willingness to pay to avoid a certain health risk. Usually the numerous existing contingent valuation studies are analysed to derive monetary values per health endpoint.


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Figure 11.2: Ranking of the considered measures ranked by avoided DALYS for the EU27 area in 2030 and 2050

Figure 11.3: Ranking of the considered measures ranked by avoided DALYS for the PARIS area in 2030 and 2050 The ranking of measures with the most avoided DALYS in 2030 for the whole European domain are:

Combined climate protection measures in cement industry Replacement of solid fuels fired small combustion plants with efficient combustion

techniques energy-efficient modernisation of old buildings

The ranking of measures with the most avoided DALYs in 2050 for the whole European domain are:



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energy-efficient modernisation of old buildings Combined climate protection measures in cement industry

The ranking of measures for the specific 1st level MCs are the following: Rhine-Ruhr area (focused year 2030)

energy-efficient modernisation of old buildings Replacement of solid fuels fired small combustion plants with efficient combustion

techniques Combined climate protection measures in cement industry

Rhine-Ruhr area (focused year 2050) Replacement of solid fuels fired small combustion plants with efficient combustion

techniques Combined climate protection measures in cement industry Expansion of district heating networks

Po Valley (focused year 2030)

Combined climate protection measures in cement industry energy-efficient modernisation of old buildings kerosene tax for aviation

Po Valley (focused year 2050) energy-efficient modernisation of old buildings Combined climate protection measures in cement industry Replacement of solid fuels fired small combustion plants with efficient combustion

techniques London (focused year 2030)



London (focused year 2050) Replacement of solid fuels fired small combustion plants with efficient combustion

techniques energy-efficient modernisation of old buildings Switch to renewable heat supply in residential sector

Paris (focused year 2030)



Paris (focused year 2050) Replacement of solid fuels fired small combustion plants with efficient combustion

techniques energy-efficient modernisation of old buildings Switch to renewable heat supply in residential sector

Additional notes: − Differentiation between mono-centric and poly-centric urban regions is necessary.


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− While the implementation of small scale policies/projects is possible under both conditions, it is easier to implement regional projects (e. g. ventilation areas/regional green spaces), when there is an superordinated administrative structure for the whole metropolitan region. This could be a top-down (like in London, where the GLA generates urban development plans for the whole city and the local planning authorities must consult the Mayor on planning applications that are of potential strategic importance for the whole of London) or bottom-up structure (like the the legally binding “Regionalplan Ruhr”, which is resulting from the cooperation of some cities in the Ruhr area, called “Ruhr 2030”).

− To have an influence on the air quality in cities it seems to be the most effective to combine local and regional actions. Regional cooperation could also help to make sure that local projects do not counteract each other and/or local knowledge/developments can be shared.

− In order to implement bottom-up strategies (esp. if there is no over regional administrative structure) it is necessary to inform and participate the local stakeholders (politicians, administration, economy, the public, NGOs...) in order to gain their understanding and acceptance as well as/or active support.

− In order to reach the political aims, different governance instruments can be used:

A. regulatory instruments → urban and regional land use planning, urban development contracts regional planning procedures, plan approval procedures...

B. economic instruments → taxes/charges, subsidies... C. informal/communicative instruments → Leitbilder (models), workshops, target agreements,

Climate-Proofing, organisational development (e. g. NGOs, neighbourhood agreements) For more information please see:


1.4. Potential Impact, Main Dissemination Activities and Exploitation Results The project is contributing to the strategic goal of promoting sustainable management of the environment and its resources by advancing our knowledge on the interactions between air quality, climate and human activities, all in relation to large urban centres and hotspots. Megacities constitute major sources of anthropogenic air pollution and hence affect the lives of hundreds of millions of people in the world directly by the quality of air that they breathe and through complex interactions resulting in climate change. Research within the project has led to improved modelling and assessment tools. In particular, MEGAPOLI has formulated a European methodology for integrated air quality and climate assessment over multiple scales (urban to global). MEGAPOLI places particular emphasis on the interactions between air quality and climate change impacts resulting from megacities on regional to global scales and potential mitigation options. This has led to an integrated methodology and corresponding tools to assess these impacts both in Europe but also elsewhere. MEGAPOLI has achieved significant scientific innovations, including:

(i) Integration of the interactions and processes affecting air quality and climate change on regional to global scales coupled with the capability of estimating the human, ecosystem and economic impact of air pollution resulting from megacities;


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(iii) Integration of ground-based, aircraft and satellite technologies with state-of-the-art modelling tools;


(v) Integration of knowledge and practical implementation of improved tools according to the level of complexity for a range of megacities and hotspots;


(vii) Development of an integrated assessment methodology for supporting EU and global policy frameworks. This will be achieved through the assessment of mitigation options and the quantification of impacts from polluted air-masses on larger scale atmospheric dynamics;

(viii) Examination of important feedbacks among air quality, climate and climate change; (ix) A robust, global information dissemination gateway on air quality, climate change and

mitigation and policy options for European stakeholders strengthening the European Research Area (ERA).

MEGAPOLI significantly extends the current state-of-the-art in the assessment capabilities within Europe by developing and implementing reliable integrated tools on multiple scales and for multiple pollutants. These are applied to assess directly the impact of the largest urban centres and hotspots in Europe and globally by employing highly advanced as well as simpler tools. The project brings together current off-line approaches as well as new on-line methods, enabling feedbacks to be quantified on multiple scales and thus mitigation options to be examined more effectively. The main conclusions and recommendations can be summarized as follows:

1. MEGAPOLI studies showed that highly detailed local inventories would be needed in order to correctly quantify the emissions from megacties and the exposure to pollution in megacities. The higher total emissions in megacities lead to higher exposure levels, despite the lower emissions per capita, since the population is in the direct vicinity of the source, which could be responsible for many different health effects, such as asthma in children.

2. The results from MEGAPOLI studies show that the pollutants from megacities are transported over regional and even intercontinental scales and contribute to the pollution levels in other specific regions. It is found that megacities in Europe are the main contributors to deposition of aerosols (especially absorbing aerosols like soot) in the Arctic, both for the annual and the wintertime deposition.

3. The dominant process reducing the concentration of air pollutants when pollutants are dispersed away from megacities was found to be dilution; the rate of dilution depends strongly on meteorological conditions. Air pollutants undergo physical and chemical changes as they are transported away from megacities; this contributes to increased levels of ozone and secondary particulate matter in nearby regions downwind of megacities.

4. MEGAPOLI has led to improvements in our understanding of megacity emissions, but recommends that to determine these more accurately, more work is needed, such as establishing an inventory development level, improving knowledge about differences between the megacities and the remainder of the country, such as in fuels, fuel quality and appliance types. The megacity emissions analysis showed very distinct characteristics in the main sources of pollutants depending on the geographical regions where the megacities are located.


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5. Using a simple analytical technique based on the climate sensitivity computed by complex models, MEGAPOLI estimated that megacities contribute a warming of over 0.2 K after 100 years, with nearly 90% of this due to carbon dioxide emissions, and most of the remaining 10% due to methane.

6. It is found that the contribution of megacities to global pollutant emissions is of the order of 2% - 6% of the total global annual anthropogenic emission flux; however, megacities have a disproportionately smaller impact on air pollutants, especially ozone, for which the global burden changes by < 1% when megacity emissions are removed from the simulations.

7. The MEGAPOLI results showed that the growth of megacities will considerably affect future urban climate; the analysis of the impact of pollutants such as NOx, VOC and aerosols from megacities on climate under future conditions suggested that, compared to today, the total forcing of these atmospheric pollutants is slightly positive at +0.4±0.11 mW/m2 with a warming impact on future climate that adds to the much larger impact from CO2.

8. The studies in MEGAPOLI found that the large-scale circulation in the Northern Hemisphere causes megacities in Europe, especially Saint Petersburg, Moscow and the Ruhr Valley to be the most significant contributors to deposition of aerosols (especially absorbing aerosols like soot) in the Arctic; the strong winds in mid-latitude cyclonic and anti-cyclonic systems, along with suppressed vertical mixing, result in strong long-range, near-surface export of pollutants.

9. The MEGAPOLI studies indicate that indirect effects of aerosols significantly modify meteorological parameters, such as daytime temperatures and height of the planetary boundary layer. NO2 concentrations are moderately affected and the direct aerosol effect was found to have substantial impact on the turbulence of the flow near the surface. For coastal megacities, increases of land temperature induced by climate change can lead to more intensive and frequent sea breeze events and associated cooler air and fog.

10. MEGAPOLI recommended a hierarchy of urban canopy models/parameterisations for different model types and scales. For urban air pollution, from traffic emissions and for the modelling of cases of emergencies (e.g., accidental releases), there is a great need of vertical profiles of the main meteorological parameters and the turbulence characteristics within the urban canopy. A large number of urban surface energy balance models now exist with different assumptions about the important features of the surface and exchange processes that need to be incorporated.

11. The integrated framework examples in MEGAPOLI show successful application of integrated models to investigate air quality affecting megacites, but a number of further research developments are needed. MEGAPOLI recommended working towards better consistency in the use of data for megacities, moving towards online or coupled approaches and addressing the need for dedicated and targeted data sets for model evaluation purposes. Prediction of PM remains a challenge and is an important area for continued research. The sensitivity of air quality to feedbacks from climate change interactions needs to be quantified; this will require online coupled models.

12. In order to reduce pollutant emissions and exposure, MEGAPOLI recommends switching to a renewable heat supply in the residential sector (reducing especially domestic wood burning), a Europe-wide passenger car toll, expansion of electricity generation from renewables in large combustion plants, replacement of solid fuel fired small combustion plants with efficient combustion techniques, replacement of old gas/oil boilers with modern condensing boilers in the cement industry, combined climate protection measures in the cement industry and promotion of low emission vehicles (E-cars, hybrid vehicles) on a midterm (2030) as well a long term time scale (2050). The measure "energy-efficient modernisation of old buildings" has been identified also as very cost efficient, but is not recommended because of the non- negligible additional health impacts from accumulated indoor pollutants in insulated buildings.


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In particular the MEGAPOLI Project contribution for EU Air Policy Review is the following: 1. Emission inventories and uncertainties Emission inventories are not consistent across scales. This is not surprising, but it is now quantified, and found to be more extreme than expected, supported by the results of the MEGAPOLI study. For important health relevant pollutants like PM the discrepancy between down-scaled and bottom-up inventories for major cities can be up to a factor of 3-4. This has important consequences for: assessing the urban increment in pollution, calculating related exposure, providing policy advise on sources to be most prominently mitigated, and predicting expected impacts of emission reductions. There is a need for further harmonization of emission inventories across Europe (countries may still report quite different definitions of the same source). 2. PM specification It is highly recommendable to include an air quality guideline or something similar (a cap) for soot or black carbon. This gives a much stronger gradient in cities and a handle on health relevant PM. Although properly measuring EC is more expensive and complicated than PM at first, in the end it is much more a comparable metric which does not mix up mineral dust, sea salt, combustion particles and secondary (in)organic aerosols. This would make policies more targeted and the impact of policies easier to quantify and justify (& less obscured by all the natural aerosols). Related to the above it would be good to move from a PM10 and PM2.5 AQ limit value to a coarse (PM2.5-10) and fine (PM2.5) particulate matter limit value. Again this will make measures and impacts more concrete and transparent in their effectiveness. PM10 is currently really messy because all the secondary PM2.5 is included and it is hard to separate between differing sources such as mineral dust events and resuspension. In-city measures to reduce emissions and/or resuspension will show up as much more successful when expressed as a fraction of "PMcoarse". At the same time places where PMcoarse is very low do not need such measures; although this seems obvious, it is actually not normally treated this way, since normally only a PM10 concentration figure is available to work with. 3. Ozone produced from megacity emissions The effect of megacities emissions on global O3 and OH is very small (less than 1%), although this comes about partly from compensating changes (often increases in the cities and decreases downwind); the impact on global O3 chemistry probably does not deserve much more study beyond MEGAPOLI, though regional and city-scale studies still make sense for specific measures in cities with high O3 levels (e.g., Chinese megacities). The chemical intricacies of ozone formation can often lead to the maximum ozone levels to be observed downwind of megacities, a well-known phenomenon. However,O3 production is a more complex function of VOC speciation than previously considered; in particular, many VOCs begin producing significant amounts of ozone after a delay of a day or more, so that they would not be accounted for in many traditional O3 production potential estimates. 4. Secondary organic aerosols Secondary organic aerosols are a very important part of air pollution from megacities. The change in the chemical composition of aerosols as they are transported away from megacities is quite substantial. The evaporation of the semi-volatile (hydrocarbon-like) organic compounds from existing particles and their subsequent oxidation in the gas phase leading to the production of condensable secondary particulate matter together with the more traditional formation of secondary organic PM (from VOCs like the monoterpenes, aromatics, isoprene, etc) leads to a change of the OA from initially resembling emissions from combustion sources to a very oxygenated mixture of


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compounds. As a result, the organic PM exported by megacities is quite different chemically from that emitted by the sources inside the city. The aged organic PM is a lot more hygroscopic and less volatile than the original PM. This build-up of secondary pollutants was clearly observed several times during the MEGAPOLI Paris campaign research flights crossing the pollution plume, in this case heading to the north. 5. Long-range transport and regional pollution Experimental observations and modelling activity results showed that air quality levels within megacities and hot spot areas in Europe are influenced by long range transport and regional pollution (particularly relevant effects are detected for PM10). Coordinated measures need to be planned in nearby or reciprocally influencing areas (even located in different states) to be able to achieve compliance to air quality standards in critical regions. Stand-alone local measures can be expected to be frequently ineffective. Although the bulk of aerosol outflow plumes tends to be within a few hundred km of the megacities, the final deposition of megacity aerosol emissions is much more long range: in MEGAPOLI we have shown that on average 50% of the mass of small aerosol particles (r < 1 um) is deposited more than 1000 km away from their source; however, for individual cities, the dispersion of pollution makes this not so evident in atmospheric concentration fields. Thus, for pollution regulations, the cumulative large-scale interconnectivity still needs to be better considered for understanding the effects of deposition (e.g., health, crop damage, structural damage, etc.). 6. Megacity effects on climate The carbon dioxide emissions dominate the climate change impact from megacities. The largest carbon dioxide emissions come from U.S. and East Asian cities. Within Europe the largest emissions come from disperse industrial regions such as the Rein-Ruhr and Po Valley, rather than from individual cities. Megacities are also producing a strong anthropogenic heat flux and can be warmer than surrounding rural environments by several degrees, up to 10°C. This heating obviously impacts the local environment directly, but also profoundly affects the regional air circulation, which is changed additionally by an increase in the so-called roughness length due to the building height and density. It was estimated that megacities contribute a warming of over 0.2 K after 100 years, with nearly 90% of this being due to carbon dioxide emissions, and most of the rest due to methane. The contribution of megacities to global pollutant emissions is of the order of 2% to 6% of the total global annual anthropogenic emission flux. There are four main direct radiative forcing impacts of megacity non-CO2 pollutant emissions: (i) Ozone production: +5.7±0.02 mW/m2; (ii) Reduction of the methane lifetime due to OH radical production: -2.1±0.13 mW/m2; (iii) Short-wave direct forcing from aerosols: -6.1±0.21 mW/m2; (iv) Long-wave direct forcing from aerosols: +1.5±0.01 mW/m2. The combined effect of all of these individual terms is a rather small negative forcing, that is a cooling, of -1.0±0.32 mW/m2 under present-day conditions. As a result the effect of megacities on global climate is very small. 7. Climate change effects on air quality The direct impact of climate change on air quality in megacities is significant due to changes in temperature (BVOC fluxes, wild fires, deposition, O3, CH4, SOA, pSO4, pNO3), radiation (photolysis), clouds, and precipitation. As climate changes, ozone concentrations will further increase, unless emission reduction measures are implemented. However, the expected emissions reduction during the next several decades is much stronger than the ozone increase due to climate change expected in the most megacities regions studied within the project. Only a more frequent appearance of extremes like heat waves under the climate change might bring air quality problems with them, e.g. exceedances of limits of ozone concentrations on local or regional scales.


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8. Baseline scenario and efficient measures for improving air quality and climate change impacts in megacities MEGAPOLI applied a complex scenario approach with an energy model and emission inventory to perform an integrated assessment for European megacities. The multi-pollutant, multi-source and multi-scale impacts of measures were taken into account, as well as the relationship between climate change and air pollution. A major finding is that several European countries will not achieve the future threshold requirements of the Air Quality Directive (2008/50/EC) or the National Emission Ceilings (NEC) defined in the NEC directive (2001/81/EC), even with additional measures, especially for particulate matter (PM10 and PM2.5); the climate policy scenario in combination with the maximum feasible reduction scenario for 2020 comes closest to these requirements. The most efficient measures for improving air quality and climate change impacts in European Megacities by 2030 and 2050 are: - Switching to renewable heat supply in residential sector [2030/2050] - Implementing a European-wide passenger car toll [2030/2050] - Expanding electricity generation from renewables in large combustion plants [2030/2050] - Replacing solid fuel fired small combustion plants with efficient combustion techniques [2030/2050] - Replacing old gas/oil boilers with modern condensing boilers in small combustions [2030] - Implementing combined climate protection measures in the cement industry [2030] - Promoting low emission vehicles (E-cars, hybrid vehicles) [2050] Finally, there are many complexities involved in the interpretation, for instance the difference between developed and developing countries, and the accumulation of indoor pollutants, which strongly influences the impact on human health; as an example, the measure "energy-efficient modernisation of old buildings" has been identified also as very cost efficient, but it is not recommended due the non-negligible additional health impacts from accumulated indoor pollutants in insulated buildings. 9. Further research needs * Emissions: - There is a need for "shadow" scientific emission inventories. These should not compete with official reported data, with arguments about which is right, but rather should be the test-bed for new insights, delivered to modellers in a consistent manner across Europe to test their validity. If proven more reliable, certain aspects can be communicated to countries and/or find their way into the emission inventory guidebook. In the current set-up, new insights find their way into official reporting only very slowly, causing them to lag behind what modellers are using and what source-receptor insights we have. The simple example is spatial resolution. Since about 2008 we have been delivering EIs at ~ 7 x 7 km. It is widely recognized that 50 x 50 km is no longer acceptable, yet it is expected that official reporting at 10 x 10 km may take another 2-4 years, and still be rather incomplete. For a "new" or revisited source this process will be equally time consuming. By designing and orchestrating a good marriage between scientific and official reported EIs, much can be gained and both will profit. - There is also a need for periodic intercomparison and integration of emission inventories produced at different levels: Pan European inventories, member states national top-down inventories, sub-national regions and local bottom-up inventories. Relevant differences have been highlighted and the integration work performed in MEGAPOLI should be updated periodically on a regular basis. * Evaluation of the population exposure to air pollution and the adverse health effects in megacities, and cost-effective ways to reduce the adverse health effects:


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Issue: The previous projects have focused on the air quality and climatic effects of megacities, but haven't taken the next step to assessing the health effects. The major problem that has not yet been directly studied in the EU programmes is the mortality and morbidity of populations in megacities caused by poor air quality. Method: this should be studied by constructing chains of models from emissions to air quality to exposure to health effects. Currently, exposure modules are included only in a small fraction of the integrated modelling systems, and simplified health effects modules in very few of them. In addition to modelling, what is also needed is complementary focused measurements campaigns. Influence on EU policy: The application of such integrated modelling chains would allow for the study of cost-effective measures, policies and abatement strategies in order to ensure a sustainable development of megacities, including the health effects on the populations. * Additionally to the existing linearised and simplified integrated assessment tools a new generation of integrated meteorology/climate and atmospheric chemical transport models with two-way feedbacks are needed to analyse non-linear interactions of climate change and air quality. * Better coordination of climate change and (urban) air quality policies is needed. Stricter regulations of biomass burning for domestic heating and leisure uses within and around urbanized and critical areas are desirable. MEGAPOLI showed a great complexity of the problem for megacities, which is reflected in several ways: - multi-component (numerous gas and aerosol phase interacting constituents) - multi-aspect (air quality, climate, health, agriculture, tourism, economics) - multi-disciplinary (natural and social scientists and humanities working together on "integrated research/assessments"). Important topic for further studies: Integrated assessment and reduction strategies of both the air quality and climatic effects which could be achieved by various climatic and air quality measures, regulations and policies.

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