**7. Aerosol detection over the metropolitan region of São Paulo**

In order to track the biomass burning plume detected near the AERONET sunphotometer site in Campo Grande, backtrajectories were generated using the HYSPLIT model. Those backtrajectories show that the aerosol plumes were transported from the Midwestern region, near Campo Grande, to the Southeastern of the Brazilian territory, more precisely to the city of São Paulo, where there are two remote sensing equipments installed, the AERONET sunphotometer and an elastic backscatter 532 nm Lidar system these backtrajectories, presented in Figure 5 and Figure 11, it is possible to observe that aerosol air masses trajectories start at different altitude levels (3.5, 4.0 and 4.5 km AGL) on 21 August 2007 and move towards the Southeastern part of Brazil, reaching the MASP on 23 August 2007 at an altitude also around 3.5 and 4.5 km. The altitudes of the starting trajectories in CG region are at the same range altitude of the aerosol layers detected by the CALIOP sensor signed as biomass burning according to Figure 8.

On 23 August 2007, measurements carried out with the MSP-Lidar system, between 12:40 and 22:12 UTC, show the MASP atmosphere heavily loaded by aerosols, in addition, in Figure 12 the presence of a thin aerosol layer above the PBL can be seen from 3.5 to almost 5 km of altitude. Such vertical profile measured using MSP-Lidar system together with the backtrajectories from HYSPLIT model give a strong indication that this thin layer detached from the PBL is composed by biomass burning aerosols from the Midwestern region of Brazil.

Backscatter profile analyses were performed applying the Klett inversion method together with the AOD values retrieved by the AERONET sunphotometer. The 532 nm backscatter profile, presented in Figure 13, was calculated for the period between 17:00 to 18:00 (UTC), which corresponds to the CALIPSO closest approach to the MASP. The backscatter maximum for this measurement period was observed between 0.5 and around 2.0 km altitude range. This aerosol layer showed a quite stable maximum of 0.0033 km-1sr-1 during the period of measurements and represents the aerosol trapped in the PBL layer. The Lidar ratio in this period presents a constant value of 41 sr, calculated between 0.5 and 5.0 km range altitude, which represent the dust aerosol type [45]. Such values of LR are not consistent with those values for biomass burning; however, it should be kept in mind that the Klett's inversion method only provide a constant LR value for the whole atmosphere column; in addition, the MASP is considered one of the most polluted cities in the world, having several different aerosol types loaded in its atmosphere, which can turn the retrieval of the LR value and the confidence of the aerosol type classification very difficult tasks. Furthermore**,** the HYSPLIT backtrajectories leads to a strong indication that the detached layer between 3.5 and 5 km is the biomass burning aerosol transported from the Midwestern region of Brazil. Backscatter profile analyses performed in posterior time period (around 20:00 UTC) presents LR values of 60 sr, consistent to the biomass burning aerosol type according to [45].

264 Atmospheric Aerosols – Regional Characteristics – Chemistry and Physics

after the CALIPSO satellite overpasses.

Figure 8.

Brazil.

Two possible reasons can explain the detection of different values of AOD and LR from those values retrieved on the nighttime measurements (Figure 7). The first one is that the detected aerosols have their optical properties changed due to long-range transport, mixing with other aerosol types or absorbing moisture from the atmosphere, undergoing aging processes. The low value of the Lidar ratio (40 to 55 sr) also indicates the aging processes of the aerosols; such lower values may be linked to an increase of particle size by moisture absorption and/or a reduction of the light absorption capability of the particles [37]. However, the second reason can be the fact of the transported aerosol masses only reaches the region measured by the CALIOP sensor on 22 August 2007, a day

**7. Aerosol detection over the metropolitan region of São Paulo** 

In order to track the biomass burning plume detected near the AERONET sunphotometer site in Campo Grande, backtrajectories were generated using the HYSPLIT model. Those backtrajectories show that the aerosol plumes were transported from the Midwestern region, near Campo Grande, to the Southeastern of the Brazilian territory, more precisely to the city of São Paulo, where there are two remote sensing equipments installed, the AERONET sunphotometer and an elastic backscatter 532 nm Lidar system these backtrajectories, presented in Figure 5 and Figure 11, it is possible to observe that aerosol air masses trajectories start at different altitude levels (3.5, 4.0 and 4.5 km AGL) on 21 August 2007 and move towards the Southeastern part of Brazil, reaching the MASP on 23 August 2007 at an altitude also around 3.5 and 4.5 km. The altitudes of the starting trajectories in CG region are at the same range altitude of the aerosol layers detected by the CALIOP sensor signed as biomass burning according to

On 23 August 2007, measurements carried out with the MSP-Lidar system, between 12:40 and 22:12 UTC, show the MASP atmosphere heavily loaded by aerosols, in addition, in Figure 12 the presence of a thin aerosol layer above the PBL can be seen from 3.5 to almost 5 km of altitude. Such vertical profile measured using MSP-Lidar system together with the backtrajectories from HYSPLIT model give a strong indication that this thin layer detached from the PBL is composed by biomass burning aerosols from the Midwestern region of

Backscatter profile analyses were performed applying the Klett inversion method together with the AOD values retrieved by the AERONET sunphotometer. The 532 nm backscatter profile, presented in Figure 13, was calculated for the period between 17:00 to 18:00 (UTC), which corresponds to the CALIPSO closest approach to the MASP. The backscatter maximum for this measurement period was observed between 0.5 and around 2.0 km altitude range. This aerosol layer showed a quite stable maximum of 0.0033 km-1sr-1 during the period of measurements and represents the aerosol trapped in the PBL layer. The Lidar ratio in this period presents a constant value of 41 sr, calculated between 0.5

**Figure 11.** Air mass trajectories generated by the HYSPLIT model. Such trajectories identify the transport of aerosols from the Midwestern region of Brazilian territory on 21 August 2007 for the Southeast region of Brazil, reaching the MASP on 23 August 2007.

Impacts of Biomass Burning in the Atmosphere

of the Southeastern Region of Brazil Using Remote Sensing Systems 267

considered one of the most polluted megacities of the world, with high quantity and variety of aerosols in its atmosphere. On the other hand, the trajectory of the CALIPSO satellite took place at about 80 km of horizontal distance to the east direction of the MASP, as can be checked in Figure 5. In this case, the CALIPSO satellite must have measured different aerosol layers with different optical properties from those measured by the AERONET sunphotometer. Furthermore, the values of LR are practically constant with values of 55 sr, representing aerosols of dust or polluted dust types. Taking into account the closest distance between CALIPSO trajectory and the MSP-Lidar system site, these CALIOP LR values can be considered in agreement with that retrieved by the MSP-Lidar system, which obtained

**Figure 14.** AOD and LR distribution as function of latitude (DT trajectory in Figure 5) measured by the CALIOP sensor on 23 August 2007 during the daytime. The star marks the point of the satellite closest approach to the AERONET site installed at MASP. The red triangle in the left panel represents the value

In this study, an extensive biomass burning event observed at two different sites in Brazilian territory and track the aerosol transportation from Midwestern to Southeastern region of Brazil have been described. The synergy of MODIS and CALIOP sensor, both aboard of satellites, the AERONET sunphotometer and the elastic backscatter Lidar system measurements allowed to estimate key optical characteristics of the aerosols observed during this event. These results are important for the radiative forcing study in the Brazilian territory and for the study of the effects of certain types of aerosol in the air quality of the megacities such as São Paulo, due to aerosols produced in the MASP as well as those

Spatial distribution of fires in the São Paulo State obtained by the NOAA-12 satellite indicates that the winter is the season with the highest number of fire outbreaks. In addition, during the harvest period, which occurs from May to November, the plantation areas are burnt a few hours before the manual cutting, resulting in large quantities of aerosols being emitted into the atmosphere. AOD measurements from MODIS sensor indicate high maximum values during spring and winter (Southeastern dry season). Average of the maximum AOD between 2003 and 2010 was 0.492±0.505, indicating the high variability of the maximum AOD over this region. As in the Brazilian Southeastern region, the large

of AOD measured by the AERONET sunphotometer during the closest approach time.

**8. Conclusions** 

transported from distant regions.

values spanning from 33 to 66 sr in the whole time period (Figure 12).

**Figure 12.** Range corrected backscatter profile at 532 nm for measurements carried out on 23 August 2007 by the MSP-Lidar system between 12:48 to 22:12 (UTC). It can be seen a thin layer of aerosol between 3.5 and 5 km transported from the Midwestern region of the Brazilian territory.

**Figure 13.** Backscatter coefficient profile at 532 nm measured on 23 August 2007 by the MSP-Lidar system between 17:00 to 18:00 (UTC).

On the same day the AERONET sunphotometer installed at MASP obtained AOD values spanning from 0.20 to 0.38, indicating the detection of a high amount of absorbent aerosols loaded in the atmosphere of the MASP. Figure 14 shows the AOD and LR values obtained by the CALIOP sensor aboard the CALIPSO satellite on 23 August 2007, which overpasses the region close to MASP with closest approach of about 80 km. The CALIOP AOD values for this case are spanning from 0.08 to 0.14, which is quite low to the values retrieved by AERONET. Such difference between AOD retrieved by both instruments might have occurred due to the fact that the sunphotometer is installed within the MASP, which is considered one of the most polluted megacities of the world, with high quantity and variety of aerosols in its atmosphere. On the other hand, the trajectory of the CALIPSO satellite took place at about 80 km of horizontal distance to the east direction of the MASP, as can be checked in Figure 5. In this case, the CALIPSO satellite must have measured different aerosol layers with different optical properties from those measured by the AERONET sunphotometer. Furthermore, the values of LR are practically constant with values of 55 sr, representing aerosols of dust or polluted dust types. Taking into account the closest distance between CALIPSO trajectory and the MSP-Lidar system site, these CALIOP LR values can be considered in agreement with that retrieved by the MSP-Lidar system, which obtained values spanning from 33 to 66 sr in the whole time period (Figure 12).

**Figure 14.** AOD and LR distribution as function of latitude (DT trajectory in Figure 5) measured by the CALIOP sensor on 23 August 2007 during the daytime. The star marks the point of the satellite closest approach to the AERONET site installed at MASP. The red triangle in the left panel represents the value of AOD measured by the AERONET sunphotometer during the closest approach time.
