Supplementary material for

PARTICULATE MATTER LEVELS IN A SOUTH AMERICAN MEGACITY: THE METROPOLITAN AREA OF LIMA-CALLAO, PERU

Jose Silvaa, Jhojan Rojasa, Magdalena Norabuenaa, Carolina Molinab, Richard A. Torob and Manuel A. Leiva-Guzmánb

a National Meteorology and Hydrology Service, Casilla 11-1308, Lima 11, Perub Center for Environmental Science and Department of Chemistry

Faculty of Science, University of ChileP.O. Box 653, Santiago, Chile

We herein present additional information related to the air quality monitoring network stations

and meteorology information of the metropolitan area Lima-Callao (MALC) for the manuscript

“Particulate Matter Levels in a South American Megacity: The Metropolitan Area of Lima-

Callao, Peru”.

1. Complementary information for the air quality monitoring network stations

Table S1 shows the station names, locations, the PM measuring principles and the data

availability for PM10 and PM2.5. The data files are available at http://www.senamhi.gob.pe or by

request.

Table S1. Monitoring stations under study in the Lima-Callao Metropolitan Area (MALC)*; see Figure 1 (SENAMHI, 2016).

Station Name

StationID

Station Location

(Lat; Lon)

Altitude(m.a.s.l.) Pollutant Measuring

PrincipleMeasurement

Instrument

Data Availability (MM/YY)

From To

Campo de Marte CDM -12.0705;

-77.0432 159PM10

Oscillating microbalance Thermo TEOM1405 09/10 actual

PM25Beta ray

attenuation Thermo Beta 5014i 10/14 actual

San Borja SBJ -12.1086; -77.0078 214

PM10Oscillating

microbalance Thermo TEOM1405 10/10 actual

PM25Beta ray

attenuation Thermo Beta 5014i 10/14 actual

Puente Piedra PPD -11.8500;

-77.0700 205PM10

Beta ray attenuation Thermo Beta 5014i 04/14 actual

PM25Beta ray

attenuation Thermo Beta 5014i 04/14 actual

Carabayllo CRB -11.9000; -77.0300 200

PM10Beta ray

attenuation Thermo Beta 5014i 04/14 actual

PM25Beta ray

attenuation Thermo Beta 5014i 04/14 actual

San Martin de Porres SMP -12.0000;

-77.0800 75PM10

Beta ray attenuation Thermo Beta 5014i 04/14 actual

PM25Beta ray

attenuation Thermo Beta 5014i 04/14 actual

San Juan de Lurigancho SJL -11.9700;

-76.9800 232PM10

Beta ray attenuation Thermo Beta 5014i 04/14 actual

PM25Beta ray

attenuation Thermo Beta 5014i 04/14 actual

Huachipa HCH -12.0200;-76.9300 304

PM10Beta ray

attenuation Thermo Beta 5014i 04/14 actual

PM25Beta ray

attenuation Thermo Beta 5014i 04/14 actual

Ate ATE -12.0261;-76.9186 358

PM10Oscillating

microbalance Thermo TEOM1405 04/10 actual

PM25Beta ray

attenuation Thermo Beta 5014i 10/14 actual

Santa Anita STA -12.0433; -76.9714 282

PM10Oscillating

microbalance Thermo TEOM1405 09/11 actual

PM25Beta ray

attenuation Thermo Beta 5014i 12/14 actual

Villa María del Triunfo VMT -12.1664;

-76.9200 292PM10

Oscillating microbalance Thermo TEOM1405 01/12 actual

PM25Beta ray

attenuation Thermo Beta 5014i 12/14 actual

* data files are available from the http://www.senamhi.gob.pe database or by request to the corresponding author.

2. Complementary information for the meteorological behavior in MALC

Figure S1 shows the monthly variability of ambient temperature (T in ºC, Figure S1a), relative

humidity (HR in%, Figure S1b), wind speed (ws in ms-1, Figure S1c), predominant frequency of

the wind direction (ws 1, Figure S1d) and the base height of the thermal inversion (Figure S1e).

The following is a brief description of this variability.

Figure S1. Monthly variation of the meteorological variables measured in MALC during the study period (2010 to 2015). (b) Relative humidity (HR in%), (c) wind speed (ws in ms-1), (d) predominant frequency (freq) of the wind direction (ws) and e) base height of the thermal inversion (altitude in m).

2.1. Temperature (T in ºC, Figure S1a)

The thermal regime of the MALC approaches a subtropical climate in transition to a tropical

climate with clear maritime impact, fresh winters and very soft and weak summers. The T of the

air is influenced by the T of the sea (Schemenauer and Cereceda, 2009), with a mean T

maximum and minimum delay with respect to the solstices. The T minimum is observed in

August (16 ° C), and in February, it reaches a maximum of 24 ° C. Warming in the second half

of the year is slower than the cooling in the first half, which occurs rapidly from March onwards.

The thermal variation is stronger from April to May and slower in the months following June,

July, and August in which the lowest thermal values are reached, with an evident asymmetry

(SENAMHI, 2016). The behavior of the temperature during the day and night are abrupt with an

amplitude of variation of 6 °C in the summer months, whereas in the winter months, this

amplitude of variation decreases to approximately 4 °C due to the thermostat effect in the Pacific

Ocean (not shown here).

2.2. Relative humidity (HR, Figure S1b)

MCLA is an example of high environmental humidity within the desert climates, and the annual

average relative humidity is 82%. The relative humidity variation is regular based on the average

temperature isotherm. The observed values of the annual variations have the highest values

during the cold season; the maximum (86%) is in July, and the minimum is in February (77%),

see Figure S1b. Normally, this maximum RH is due to the intensification of the South Pacific

subtropical anticyclone, the greater force of the trade winds, totally cloudy skies and drizzles

(Capel Molina, 1999). The absolute maximum values of RH are given at the first hours of the

day when the temperature is lower, with percentages of approximately 90 to 95%; and the

absolute minimums move to the early hours of the afternoon when the heat accumulated during

the day is higher, with values from 65 to 68% in the summer months and from 72 to 78% in the

winter months (not shown here).

2.3. Wind speed (Figure S1c) and wind direction (Figure S1d)

In general, the winds are caused by the thermal differences observed between the continent and

the ocean (Enfield, 1981). Thus, in the summer months, the temperatures observed on the

continent are much higher than the measurements on the sea, which remains relatively colder,

causing a continental flow towards the coast. Hence, the clear predominance of the course

"SSW" followed by the ever wind of the South associated with the anticyclone of the South

Pacific. The north winds do not originate due to the atmospheric situations that occur at the

coast. In contrast, in winter, the thermal contrasts between the continent and the waters of the

Pacific diminish appreciably, and the atmosphere in the low layers regains its stability (Enfield,

1981). The intensification of the South Pacific anticyclone causes the winds of the South to

follow the SSE and the SSW directions. The remaining directions have little significance, and

some bearings are not recorded (N, NNE, EN and ENE) or are scarce (Figure S1d). The wind

speeds (Figure S1c) are moderate reaching an annual average of 2.4 ms-1, and the month to

month data has a regime of low variability (amplitude of 0.59 ms-1); the average speed reaches its

maximum in spring (Dec; 2.7 ms-1) and decreases in the winter season (Jul; 2.2 ms-1) when the

calm winds are much more frequent and prolonged.

2.4. Thermal inversion (Figure S1e)

Regarding the height variability of the monthly inversion layer, an annual pattern is observed in

which the average height varies from minimum values in the summer months (February to April)

with a range of 250 to 500 m to maximum values in the winter months (June to August) with a

range of 650 to 1500 m (Arellano Rojas, 2013). Large-scale subsidence results in a very stable

low troposphere and a thermal inversion of quasi-permanent subsidence. In the summer months,

the subtropical anticyclone of the Southeast Pacific moves to the south, generating favorable

conditions for the formation of coastal or dorsal lows in height that weaken the phenomenon of

subsidence and, therefore, form daily thermal inversions of the marine type. This marine type

thermal inversion produces an increase in the atmospheric temperature and a thinning of the

stratiform clouds, with a consequent increase of the solar irradiance that leads to an RH decrease

and a T increase at the surface. This causes turbulent processes to favor re-suspension of PM10,

which does not favor the formation processes of secondary particulate material. On the other

hand, in the winter, the anticyclone moves northward weakening the entry of coastal lows or

dorsal in height and therefore strengthens the subsidence phenomenon. However, there is a lower

temperature gradient between the sea and the ocean and no formation of thermal inversion at

lower heights, and the ceiling of the subsidence investment is between 650 and 1500 m due to

near-surface stability conditions (Schemenauer and Cereceda, 2009). This indicates that during

the winter the stratiform nebulosity increases, which decreases the atmospheric temperature and

the solar irradiance, and increases the RH and drizzle episodes; the conditions described favor a

significant decrease in PM10 concentrations via wet deposition and an increase in PM2.5

concentrations from the formation of secondary aerosols via the particulate gas conversion

process (Molina et al., 2017; Toro A. et al., 2014).

References

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