Fire and Smoke

Fire Case Notes - 1

How does fire affect climate?

Forest fires, brush fires, and slash and burn agriculture are a significant force for environmental change, both locally and globally.

Intentional deforestation by burning radically alters local landscapes.

At regional scales, fires naturally shape ecosystems such as the boreal forest (Canada, Alaska and Russia) and chaparral (Southern California).

Globally, fires may play an important role in climate change, emitting both greenhouse gases and smoke particles (aerosols) into the atmosphere. These emissions almost certainly played a role in the 0.5°C increase in the Earth's average surface temperature over the past 100 years.

Fire and Smoke

http://earthobservatory.nasa.gov/Library/GlobalFire/

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

http://earthobservatory.nasa.gov/Study/BOREASFire/



http://earthobservatory.nasa.gov/Library/Deforestation/deforestation_update2.html

Fire Case Notes - 2

Fire and Smoke

What changes occur when a forest or grassland fire happens?

Fire changes local & micro- scale

surface energy budget

Fire & SmokeClimate Effects

Smoke affectsradiation budget

Smoke changescloud physics

Fire changes green-house gas budget

Smoke changescloud initiationand life cycle

Fire Case Notes - 3

Radiation Primer

What is radiation?Radiation can be particles (protons, electrons, etc.) or electromagnetic waves (x-rays, ultraviolet light, visible light, etc.)

For this discussion, we will limit ourselves to electromagnetic radiation

- Electromagnetic radiation can transfer energy without requiring amedium, i.e., through a vacuum

> Other mechanisms that transfer energy, such as conduction and convection, do not work without a medium

- All objects with temperature above absolute zero emit electromagneticradiation

- Analogy of waves isoften used to describe electromagneticradiation

Height

Crest

Trough

Wavelength

Amplitude

Fire Case Notes - 4

Radiation Primer

What is the range of electromagnetic radiation wavelengths emitted by objects?

10 -14

10 -10

1

10 6

10 23

10 18

10 14

10 10

10 6

10 2

1

10 2

Frequency (hertz)

Wavelength(m)

GammaRays

Ultraviolet

Infrared

Microwaves

Short-wave

10 -2

10 -6

X Rays

Visible

TV

Broadcast Band TV - FM

Long - WaveRadio

Note: micron = m = 10-6 m



Note: Visible wavelengths range from 0.4 to 0.7 microns

Fire Case Notes - 5

Radiation Primer

What is the range of radiation wavelengths emitted by objects?All objects with a temperature above absolutezero emit electromagnetic radiation

Radiation from solid and liquid materials is emitted with a range of wavelengths similar to a histogram of scores on an exam

For radiation, this spread of energy per wavelength versus wavelength is called a spectrum

10 20 30 40 50 60 70 80 90 1000

246

8

101214

16

1820

Exam Scores

Grades0

Nu

mb

er

of

Stu

de

nts

pe

r G

rad

e I

nte

rva

l

Temperature is a measure of the average kinetic energy (energy related to motion) of the atoms and molecules in a substance

The Absolute or Kelvin temperature scales (based on the study of gases and thermo-dynamics) have a more physical meaning of zero than the Centigrade or Fahrenheit scales

An object at 0 K has a minimum of kinetic energy, not zero kinetic energy

Fire Case Notes - 6

Radiation Primer

What wavelengths does the Sun emit?

Below is the Sun’s emitted radiation spectrum; assumes the Sun’s outer surface temperature is 6000 K

Note: The Sun emits much of it’s radiation in the visible range with its wavelength of maximum emission, (max), is about 0.48 m, i.e., in the blue-green range

17,500

15,000

12,500

10,000

7,500

5,000

2,500

0 0.5 1.0 1.5 2.00.0

max

Wavelength (m)

Em

itte

d R

ad

iati

on

Per

Wav

ele

ng

th I

nte

rva

l(C

al -

cm

-2 -

min

- m

m -1

)

Visible Note: 1 calorie = energy required to heat 1 gm of water 1°C

Note: 1 Calorie (capital C; Unit used for food derived energy) = 1000 calories (lower case c) = 1 kilocalorie

95% of the Sun’s emitted radiation is in the region between 0.25 and 2.5 m

Fire Case Notes - 7

Radiation Primer

What wavelengths does the Earth emit?

Below is the Earth’s emitted radiation spectrum; assumes the Earth’s surface temperature is 288 K

Note: The Earth’s wavelength of maximum emission, (max), is about 9.8 m

95% of the Earth’s emitted radiation (gray area) is in the region between 2.5 and 25 m, i.e., at much longer wavelengths

0 10 20 300

0.025

0.050

Wavelength (m)

max

Em

itte

d R

ad

iati

on

Per

Wa

vele

ng

th I

nte

rval

(Cal

- c

m-2

- m

in -

mm

-1 )

Note: Energy amounts per wavelength interval much smaller than for the Sun

Fire Case Notes - 8

Radiation Primer

What happens to radiation when it interacts with an object?

Transmission - Energy passes through material basically unchanged, i.e., unchanged energy and wavelength

- Note: direction may be bent bythe process of refraction

Reflection or scattering - Both redirectradiation without changing the energy or wavelength

- Scattering redirects radiation in all directions, frequently has more intensity in some directions than in others

- Reflection redirects radiation in a specific direction; like poolballs colliding

Absorption - Causes molecules to increase their kinetic energy, e.g., increase their temperature



http://rst.gsfc.nasa.gov/Intro/Part2_3html.html

Fire Case Notes - 9

Radiation Primer

What happens to solar radiation when it encounters the Earth’s atmosphere?

It is

- absorbed by atmospheric gases, - scattered from atmospheric gases,- transmitted through atmospheric gases to the Earth’s surface,- absorbed by clouds,- reflected by clouds,- transmitted through clouds to the Earth’s surface,- scattered by aerosols,- absorbed by aerosols,- transmitted through aerosols to the Earth’s surface, - reflected by the Earth’s surface,- absorbed by the Earth’s surface.

Fire Case Notes - 10

Radiation Primer

How does atmospheric composition affect these processes? Most gases and aerosols (particulates - dust, salt particles, smoke, pollen, air pollution, products from volcanic eruptions, etc.) scatter solar radiation and thus, tend to increase the atmosphere’s albedo, i.e., cause the atmosphere to reflect more solar energy back to space, thus reducing the energy reaching the Earth’s surface

- Particles the size of atmospheric gas molecules (much smaller than the wavelengths of the center of the solar radiation spectrum) scatter shorter wavelengths much more than longer wavelengths; reason for blue skies and red sunsets

- Particles larger than the wavelengths of solar radiation scatter all visible wavelengths equally; reason for haze and skies that are milky and less blue

http://eospso.gsfc.nasa.gov/ftp_docs/NASA-Facts-Aerosols.pdf


Radiation Primer

How does atmospheric composition affect these processes? (Con’t) Example - Great Smoky Mountains

Clear Day Hazy Day http://www.epa.gov/oar/vissibility/what.html

Particles such as sulfates and salt particles (left by evaporating sea spray) grow during humid conditions, becoming larger than the wavelengths of visible radiation. Natural sources of haze-causing pollutants include dust, and smoke from wildfires. Manmade sources include vehicles, electric utility and industrial fuel burning, and manufacturing. Some haze-causing particles are formed from gases and particulates emitted many miles upwind.


Radiation Primer

Aside: How do clouds affect these processes?

Clouds (typical droplets are about 50 times larger than the wavelengths of visible light) reflect, absorb and transmit radiation

- Clouds are very good reflectors of solar radiation. Percentage of solar energy reflected related to the cloud depth

Cloud depth (m) Albedo (%)

100 751000 85

- Clouds are not very good absorbers of solar radiation. Amount of absorption related to the cloud depth

Cloud depth (m) Absorption (%)

100 51000 10


Radiation Primer

What happens to solar radiation when it encounters the Earth’s atmosphere?

Global solar radiation budget

Most (55%) visible radiation reaches the Earth’s surface

Incoming SolarRadiation 100%

Total Albedo 30%

3% Absorbedby Clouds

16% Absorbedby Air

4% Reflectedfrom Surface

20% Reflectedby Clouds

6% Scatteredby Air

25% Direct

26% Diffuse

51% Absorbed at theEarth's Surface

Air here refers to the gas molecules and particulates


What happens to solar radiation that reaches Earth’s surface?

Absorbed or reflected

- Examples:Albedo or

Material Absorption ReflectionFresh Snow 25-5% 75-95%Old Snow 60-30% 40-70%Sea Ice 70-60% 30-40%Desert 75-70% 25-30%Glacier Ice 80-60% 20-40%Grass 84-74% 16-26%Crops 85-75% 15-25%Deciduous Forest 85-80% 15-20%Tundra 85-80% 15-20%Soil 85% 15%Water (Low Sun) 90-0% 10-100%*Asphalt 94% 6%Coniferous Forest 95-85% 5-15%Water (High Sun) 97-90% 3-10%*

*albedo of water depends on the solar angle and sea surface roughness (daily average given). Low angle more albedo.

Earth Surface Energy Primer


What happens to solar radiation that reaches Earth’s surface? (Con’t)

Composited Surface Albedo - MODIS 16-day composited surface albedo, from April 7-22, 2002

• White indicates no data and no albedo data are provided over oceans



http://earthobservatory.nasa.gov/Newsroom/NasaNews/2002/200207099816.html


Note: This is surface albedo

Where are the regions with the highest albedo?

What type of surfaces do

these regions have?

QuickTime™ and aTIFF (LZW) decompressor



What happens to solar radiation that reaches Earth’s surface? (Con’t)

Reflected Solar Radiation (W/m2)

Winter solstice, 22 December 2004

Summer solstice, 20 June 2005




Note: These images are top-of-atmosphere reflected energy as seen by satellite, not surface only reflected

energy

What dominates the albedo in these images?

http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17130


How does the Earth’s surface cool?

Conduction - Into ground

- Averages to zero over a year; into ground spring/summer, out of ground fall/winter

Convection - Important cause of weather

- About 20% of the energy leaves the Earth’s surface by two types of convection< Latent heat (Evaporation) - about 75% of the 20% < Sensible heat (Temperature change) - about 25% of the 20%

§ Definition - Bowen Ratio (BR) is the ratio of the sensible heating to latent heating, i.e.,

Bowen Ratio = Sensible Heating Latent Heating

- From above, the Earth’s average BR = 25% / 75% = 0.33

Radiation - Remaining 80% of the energy leaves the Earth’s surface by “longwave” radiation




How does the Earth’s surface cool? (Con’t)

The Bowen Ratio (BR) varies depending on the surface type and meteorological conditions

Geographical Area Bowen RatioEurope 0.62Asia 1.14North America 0.74South America 0.56Africa 1.61Australia 2.18Atlantic Ocean 0.11Indian Ocean 0.09Pacific Ocean 0.10All land 0.96All oceans 0.11

Note: Dry areas like Australia have high BR while wet areas like oceans have low BRs, i.e., over dry areas, more energy is transferred from the surface to the atmosphere via sensible heating while over wet areas, more energy is transferred to the atmosphere via evaporation of water




Example: Dense irrigated poplar tree farm (red) next to arid natural vegetation in northeastern Oregon

Note: In the watered, treed area has a surface temperature of 33°C (low Bowen ratio) while the dry natural areas (high Bowen ratio) have surface temperatures of 59.8°C and 60.4°C

Eos, Vol. 87, No. 43, 24 October 2006

60.4°C

59.8°C

33°C



Example: Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images on 8/27/06

- Top vegetation index, a measure of plant density

< Dense vegetation is dark green

< Sparse vegetation is pale green

- Bottom is surface temperature

Note contrast between irrigated (low Bowen ratio) And non-irrigated (high Bowen ratio) land, irrigated crop lands are much cooler, 30°C (54°F) cooler, than surrounding native vegetation





16°C 48°C


Fire and Smoke

What are the local climate effects of a fire?

What changes in surface characteristics occur when a fire happens?

- Changes from a living, green, vegetated to a lifeless, blackened surface

Vegetated vs Burned

Forest or grassland?Effect on albedo?

Effects on greenhouse gases?

Short- or long- termeffects?

Effect on Bowen ratio?

Tropical, midlatitude orboreal region?

Albedo is the amount of electromagnetic energy reflected divided by the amount of incident energy

Bowen ratio is the ratio of the sensible heating to latent heating


Fire and Smoke

How does a change from a green vegetated surface to a black charred surface change the local radiation balance?

Spectral response depends on surface

Leaves reflect green and near IR; absorbs other wavelengths

IncidentRadiation

Reflected

Absorbed

Transmitted

95% of solar energy

Note: Average reflectance of bare soil over the range of 95% of the emitted solar energy is higher than that of a vegetated surface

Thus, it might be expected that the albedo-effect of the burned surface would be to cool the surface temperature in the burned area


Fire and Smoke





How does smoke affect the balance of greenhouse gases?(Con’t)

Govaerts, Y.M.; B. Pinty, A. Lattanzio, 2003: Impact of vegetation fires on surface albedo dynamics and absorbed solar radiation over the African Continent, Geoscience and Remote Sensing Symposium, 2003. IGARSS apos;03. Proceedings. 2003 IEEE International. Volume 3, Issue, 21-25 July 2003 Page(s): 1576 - 1578. (http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel5/9010/28603/01294180.pdf}

20

0% 20%

0

Note: Lower albedo, more solar energy absorbed at surface - thus warmer

Because burned surface is black?


Fire and Smoke

How does a change from a living surface to lifeless surface change the local radiation balance? (Con’t)

Example: Results from MODIS albedo data from the years 2000 through 2004 from interior Alaska

First decade after fire, spring albedo (March and April) increased by 0.165 as compared with unburned areas that served as a control. Summer albedo (June and July) shows an initial decrease of 0.023, which recovers in five years, followed by an increase of 0.025. Spring albedo reaches its maximum at nine years since fire while the summer albedo maximum is at 20 years.

Both spring and summer albedos recover to pre-fire levels in 49 to 51 years. When converted to radiative forcing, these sustained increases in both summer and winter albedo could offset the heating from greenhouse gasses released during the fire.

Post-fire changes in surface albedo associated with vegetation succession in boreal forest ecosystems. A.E. Lyons, Y. Jin, and J.T. Randerson, University of California, Irvine. (http://adsabs.harvard.edu/abs/2005AGUFM.B33E1096)


Fire and Smoke

How does a change from a living surface to lifeless surface change the local radiation balance?

Example: In boreal region post-fire ecosystem affects the albedo in several ways

• Loss of the canopy overstory leads to greater snow cover and higher surface albedos during spring

• Grasses and deciduous trees that tend to establish in early and intermediate stages of succession have a more reflective canopy than mature black spruce ecosystems

Post-fire changes in surface albedo associated with vegetation succession in boreal forest ecosystems. A.E. Lyons, Y. Jin, and J.T. Randerson, University of California, Irvine. (http://adsabs.harvard.edu/abs/2005AGUFM.B33E1096)

Boreal Region - “The northern boreal ecoregion accounts for about one third of this planet's total forest area. It is comprised of a broad circumpolar band which runs through most of Canada, Russia, Scandinavia and parts of Northern Scotland.”

http://www.sierraclub.org/ecoregions/boreal.asp




Fire and Smoke

How does a change from a living surface to lifeless surface change the local radiation balance?

Example: Study focused on physical changes to an Australian savanna landscape caused by fire and the resultant effects of fire scars on boundary layer heating

• Albedo values were found to almost halve after fire ranging from 0.12 pre-burn to 0.07 post-burn

• Fundamental change in energy partitioning, with a reduction in evapotranspiration and an increase in sensible heating to the atmosphere

- Evident in recorded Bowen ratio (sensible/latent heat flux ratio)

for the pre-burn landscape of 2.5 compared with 6.1 post-burn

* Burnt site (fire scar) exhibited a warmer (~2°C) and a drier atmosphere near the surfaceLand surface modification by fire of tropical savanna and feedbacks to climate - N.J. Tapper, V.

Clayton, J. Beringer, A. Lynch, C. Wendt, and L. B. Hutley, Monash University, Melbourne, Australia. (http://ams.confex.com/ams/Annual2005/techprogram/paper_82869.htm)


Fire and Smoke

Laboratory Experiment

In addition to the output of and the distance from the energy source, surface type (surface reflectivity, specific heat, etc.) affect the absorption of incident radiation and how incident energy changes the temperature of a surface.

In this lab you will examine the effect of various types of “surfaces” on the time rate of change of temperature of those surfaces when they are exposed to incident “sunlight”. Recall that an object’s change in temperature, T, is related to the object’s mass, M, the specific heat of the object, csh, and the energy the

object absorbs and uses to change its temperature, E, i.e.,

T = E / ( csh M ) .

Surface reflectivity impacts the amount of incident radiation that is used to change the surface’s temperature, i.e., the surface’s reflectivity contributes to determining E in the above relationship. For example, if the surface were highly reflective, then little of the incident radiation would be absorbed and used to warm the surface. Mathematically, we can express this relationship for a dry surface as

E = (1 - Albedo ) * (Incident Radiation),

where Albedo is defined as the fraction of incident energy that is reflected, i.e., albedo is the amount of electromagnetic energy reflected divided by the amount of incident energy.


Fire and Smoke


Smoke and aerosol particles from fires can rise high into the troposphere and be carried long distances by the wind. Smoke plumes from Mexico have traveled as far north as Wisconsin and the Dakotas, and as far east as Florida and out over the Gulf Stream.

Effects of aerosols represent one of the greatest uncertainties regarding climate change, both on global and regional scales. http://earthobservatory.nasa.gov/Library/GlobalFire/fire_4.html

August 13, 2007http://earthobservatory.nasa.gov/

Newsroom/NewImages/images.php3?img_id=17744


are needed to see this picture. August 13, 2007http://earthobservatory.nasa.gov/

NaturalHazards/natural_hazards_v2.php3?img_id=14443


Fire and Smoke


Scientists do not fully understand the magnitude of their cooling influence on climate. Scientists do not know which of the emission products exerts the greater net effect on regional and global climate—the cooling influence of aerosols and clouds, or the warming influence of the greenhouse gases. Because both types of emission products change rapidly through time and space, they are difficult to observe and characterize. In the future, the greenhouse gas warming is expected to dominate due to the gases' much longer presence in the atmosphere (10-100 yrs.) than that of aerosol particles (7 days).

http://earthobservatory.nasa.gov/Library/GlobalFire/fire_4.html


Fire and Smoke

How does smoke affect the solar radiation budget?

Typically, the “direct effect” of most smoke is to increase the atmospheric reflectivity as compared to that which would have occurred without the aerosols.


Total Albedo 30%


16% Absorbedby Air



6% Scatteredby Air

25% Direct

26% Diffuse


Note: If smoke, clouds or other aerosols increase the atmospheric albedo, then

- the percent of incoming solar radiation scattered will increase,

- less energy will reach the Earth’s surface,

- the surface will not get as warm.


Fire and Smoke

How does smoke affect the solar radiation budget? (Con’t)

However, soot or “black carbon” smoke, which is generated from traffic, industrial pollution, outdoor fires and household burning of coal and biomass fuels, behaves differently. Soot is also a product of incomplete combustion, especially of diesel

fuels, biofuels, coal and outdoor biomass burning.

The bulk of most black carbon particles are less than 1 micron in diameter. Because the particles are so small, they have an atmospheric residence time of a few days to several weeks and may therefore spread over distances of 100s to 1000s of km before they fall back to Earth.

Soot mainly absorbs solar radiation rather than scattering it. This causes the layer of atmosphere containing the black carbon to warm more than without black carbon. The Earth’s surface will be cooler as less solar energy is still reaching the surface.

http://earthobservatory.nasa.gov/Newsroom/NewImages/Images/baghdad_ast_2003090_lrg.jpg

http://www.earthinstitute.columbia.

edu/events/aep/

2004/documents/

David_G_Streets.pdf




Fire and Smoke


“Both soot and the light-colored tiny particles, most of which are sulfates, pose problems for air quality around the world. Efforts are beginning to reduce the sulfate aerosols to address air quality issues.’There is a pitfall, however, in reducing sulfate emissions without simultaneously reducing black carbon emissions,’ Hansen said. Since soot is black, it absorbs heat and causes warming.

Sulfate aerosols are white, reflect sunlight, and cause cooling. At present, the warming and cooling effects of the dark and light particles partially balance.”http://earthobservatory.nasa.gov/Newsroom/NasaNews/2003/2003051314856.html

Fig. 1: From left to right, pollen, ash (from a Malaysian forest fire in 1997), and soot as viewed under a scanning electron microscope. This gives an idea of the different sizes and shapes of aerosol particles.

Images courtesy U.S. Environmental Protection Agency. (Image credit: Bob Williams)

Aerosols: More Than Meets the Eye - http://www.nasa.gov/pdf/135640main_aerosols_trifold21.pdf 10 m 10 m3 m


Fire and Smoke


Black Carbon Smoke Over Alaska 15 August 2005 - An area of high pressure with calm surface winds, as is often the case, built up over Alaska in August. This high pressure system coincided with a period with more than a hundred forest fires

churning out thick smoke. Increasing amounts of smoke are shown in this Ozone Monitoring Instrument (OMI) image from NASA’s Aura satellite as an aerosol index with shades of blue (little or no smoke) to dull red (thick smoke).



Fire and Smoke


Smoke includes carbon dioxide, carbon monoxide, water vapor, particulate matter among other things. OMI tracks black carbon particles, or soot,that absorb ultraviolet (UV) radiation. By measuring the

amount of UV radiation the soot absorbs, OMI estimates of theamount of black carbon aerosol is in the smoke layer.

Measuring how much radiation aerosols absorb is important when trying to calculate the net effect of aerosols on Earth’s energy budget and

climate.

Recall, UV is electro-magnetic radiation with wavelengths just shorter than violet in the visible range

http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17012http://earthobservatory.nasa.gov/Newsroom/

NewImages/images.php3?img_id=16875

Alaskan Smoke - August 21, 2004




Fire and Smoke


In addition to the direct effect, one “indirect effect” of aerosols includes changes in the cloud droplet formation process. Cloud droplets require aerosol particles to act as a nuclei or formation site for water vapor to begin condensation when therelative humidity reaches 100% (in “pure air,” i.e., only gas molecules) condensation would not start until the relative humidity reached around 400%). More aerosol particles means more, but smaller cloud droplets.

http://science.nasa.gov/headlines/y2002/22apr_ceres.htm?list104690

What you do when driving at night in fog versus rain?

Smaller droplets are more reflective to visible light than larger droplets, thus whiter, brighter clouds consisting of larger drops.


Fire and Smoke


Typically, the “indirect effect” of smoke increases the cloud reflectivity as compared to that which would have occurred without the aerosols.


Total Albedo 30%


16% Absorbedby Air



6% Scatteredby Air

25% Direct

26% Diffuse



Fire and Smoke


The smoke may do even more than cool theEarth by scattering solar radiation and bychanging the reflectance of clouds.

A “semi-direct effect” may be that heavy smoke from burning vegetation inhibits cloud formation. Research suggests that during the August-October 2002 burning season in South America’s Amazon River basin, cloud cover decreased from about 40% in clean-air conditions to zero in smoky air.

In the morning, smoke scatters and absorbs incoming solar radiation and heats the atmosphere while inhibiting the warming of the surface.

Since the surface remains cooler, there is less convection and thus fewer clouds during the morning.

Koren I., Kaufman Y.J., Remer L.A., Martins J.V., Measurement of the effect of Amazon smoke on inhibition of cloud formation. Science, 303 (5662): 1342-1345 Feb. 27, 2004.

http://earthobservatory.nasa.gov/Newsroom/NasaNews/2004/2004030416592.html


Fire and Smoke


In the afternoon when the Sun is higher in the sky and has a higher intensity (energy per area), and since there is less cloud cover to reflect its energy, more sunlight now passes through the atmosphere and begins warming the surface.

The net effect of smoke-induced cooling in the morning and the increased warming in the afternoon, causes increased warming the surface.Koren I., Kaufman Y.J., Remer L.A., Martins J.V., Measurement of the effect of Amazon smoke on

inhibition of cloud formation. Science, 303 (5662): 1342-1345 Feb. 27, 2004.


What happens when you put a pan of water over high heat on the stove? After awhile the warmer, less dense water near the bottom begins to rise and the cooler, more dense water near the top begins to sink.

What happens if you reduce the heat on the pan bottom? The “convection” (warm water rising, cooler water sinking) slows.

Montana & Wyoming were covered by a dense smoke on 30 July 2000


Fire and Smoke

How does smoke affect these processes? (Con’t)

Recent research indicates that air pollution and smoke suppress rainfall, but cause the remaining rain amounts to fall in greater intensities, with lightning and hail.

Researchers showed that smoke from these fires delays the release of water from clouds in the form of rain, thus preventing depletion of the water in the clouds as they grow. Measurements

show that small, numerous smoke particles provide “nucleation sites” for cloud droplets, the result being that the given amount of cloud water is distributed onto many, very small drops. These drops are so small that they float with the air and don’t grow into raindrops, in contrast to the raindrop-forming processes that takes place in clouds with larger drops that form in clean air.

As these water-laden clouds reach great heights, they produce thunderstorms and hail instead of relatively moderate rain.

Raindrops are just cloud droplets that have grown to be a million times bigger



http://earthobservatory.nasa.gov/Library/GlobalFire/fire_4.html


Fire and Smoke

How does smoke affect these processes? (Con’t)

These new findings show that when the smoky and water- laden clouds develop to great heights, in excess of 10 km, these large amounts of water are also lofted and converted into ice chunks, which fall as large hailstones on the tropical rainforest. The process of hail forming is also associated with strong cloud electrification, which causes intense thunderstorms. Most of the hailstones melt during their fall, so that they arrive on the surface as spurts of intense rain.

Such impacts of air pollution are not limited to the tropical rainforests. Air pollution in general appears to change substantially the character of precipitation. This man-made climate change is already manifested by changes in the distribution of rainfall and the intensity of storms, not only over the Amazon but also over the rest of the world.

http://earthobservatory.nasa.gov/Newsroom/

NasaNews/1999/19991005712.html



http://earthobservatory.nasa.gov/Study/SmokeClouds/smoke_clouds4.html


Greenhouse Effect Primer

What is the greenhouse effect?

http://www.igpp.lanl.gov/Climate_Images/Climate13.gif



What is the greenhouse effect?

Earth's atmosphere is transparent to solar shortwave radiation, i.e., allows most of solar radiation to penetrate to the surface

Earth's atmosphere is opaque to Earth's longwave radiation, i.e., absorbs most Earth-emitted longwave radiation

How does the greenhouse effect affect a planet’s temperature?

Venus Earth MarsSurface Pressure 90 1.0 0.007

(Relative to Earth)

Main Greenhouse >90% CO2 ~0.04% CO2 >80% CO2

Gases ~1.4% H2O

Temperature (No Greenhouse) -46°C -18°C -57°C(Greenhouse) 477°C 15°C -47°CDifference 523°C 33°C 10°C

Note: Greenhouse effect (warming) is good as long as it is not overdone like on Venus. Earth is 33°C warmer. Mars could use some more greenhouse

effect.



Solar and Earth-Emitted Radiation Absorption by Atmospheric Gases

100

50

0.3 0.5 1.0 5.0 10.0 20.015.00

Wavelength (microns)

O2, CO2,H2OO3

O3

CO2

H2O

H2O

CO2,H2O

Far InfraredNear IRUV

Vis-ible

Ab

sorp

tio

n (

%)

95% ofEarth’s

Radiation

95% ofSolar

Radiation

Atmosphere is transparent to most of Sun’s

emitted radiation wavelengths

Atmosphere absorbs most of Earth’s emitted

radiation wavelengths



Solar and Earth-Emitted Radiation Absorption by Atmospheric Gases (Con’t)

Atmosphere is transparent to most of Sun’s

emitted radiation wavelengths

Atmosphere absorbs most of Earth’s emitted

radiation wavelengths



Water Vapor

Water vapor is the number one greenhouse gas

Why don’t we hear about it on TV?

Changes in Greenhouse Gases Since 1850

Concentrations of greenhouse gases in the atmosphere have risen dramatically in this century

EOS, 1999: Climate Change and Greenhouse Gases.T.S. Ledley, E.T. Sundquist, S.E. Schwartz, D.K. Hall, J.D. Fellows and T.L. Killeen. 80, p. 453.



U.S. Greenhouse Gas Emissions in 2004

U.S. greenhouse gas emissions in 2004 (million metric tons andpercentage)

- Metric tonne (abbreviated as ton) is a weight equivalent of 1000 kg> About 2205 lbs

Emissions of greenhouse gases in the United States 2004. U.S. Department of Energy, Office of Integrated Analysis and Forecasting. DOE/EIA-0573(2004) - ftp://ftp.eia.doe.gov/pub/oiaf/1605/cdrom/pdf/ggrpt/057304.pdf

Other CO2 are from non-combustion

sources

Methane is about 200 times less abundant than CO2 in the atmosphere, but molecule for molecule methane is

20 times more effective at trapping heat

A single nitrous oxide molecule is the equivalent of 206 CO2 molecules in terms of its greenhouse gas effect.


Fire and Smoke

How does fire affect the balance of greenhouse gases?

Photosynthesis by land plants plays an important role in the carbon cycle. CO2 from the surrounding air is absorbed by the tree and converted to oxygen, which is then released into the air during photosynthesis. This process results in a net removal of CO2 from the air and its storage in the tissues of plants.

In this way, carbon moves from one sphere of the Earth system (the air) to another (the land), where it is temporarily stored. (Dry wood is about 50% carbon.)

Land - Our Changing Earth; NASA Earth Science Enterprise


Fire and Smoke

How does fire affect the balance of greenhouse gases?(Con’t)

When forests die and decay or are burned, large amounts of plant tissue, known as biomass, are oxidized, and CO2 returns to the air.

Burning tropical forests releases about 10 to 20% as much CO2 into the atmosphere as the burning of fossil fuels.

The effects of that increase in CO2 ripple throughout the Earth system, and monitoring these changes by satellite is essential.

Land - Our Changing Earth; NASA Earth Science Enterprise

Fire and Smoke

Documents

Transcript of Fire and Smoke