A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Abstract submitted for presentation at the2 nd International LBA Scientific Conference, Manaus, Brazil, July 7-10, 2002What we learned about trace gases in the Amazon BasinGatti, Luciana V., Cordova, A. M.; Yamazaki, A., Trostdorf, C.R., Pretto, A.IPEN – Atmospheric Chemistry Laboratory, Travessa R, 400, CEP 05508-900,Sao Paulo, Brazil; e-mail: lvgatti@net.ipen.brArtaxo, P., Instituto de Física, Universidade de Sao Paulo, Brazil; e-mail: artaxo@if.usp.brSilva Dias, M. A. F, Departamento de Ciencias Atmosféricas, IAG-USP, SP, Brazil.Several intensive sampling campaigns were performed in 1999, 2000 and 2001, indifferent regions such as Rondonia, Manaus and Santarém as part of the LBA experiment..The wet season experiments extended from February to May and the dry season experimentsmeasured atmospheric composition associated with biomass burning emissions. The O 3concentrations were measured in parallel with CO, NOx, VOC, aerosol mass, organic carbon,light scattering and absorption. Several meteorological parameters such as solar radiation,PAR, temperature, relative humidity, wind speed and direction were also monitored.After measurements in six different campaigns, five during the wet season and one inthe dry season, it is possible to observe that the site that suffers smaller human activitiesimpacts is the Floresta Nacional do Tapajós, Para and Balbina, AM (150 km north ofManaus). The first characteristic signal of natural conditions is the small difference betweenday and night concentrations for ozone. It was also observed at the Floresta Nacional doTapajós, very frequent nocturnal peaks of high ozone concentration, that has as origin themedium troposphere.In the wet season in Amazonia, the ozone concentration in the nighttime averages 3ppb and at the peak of the radiation during daytime, it averages 15 ppb. In the dry season, theozone average concentration in the nighttime was 12 ppb and in the daytime (14:00 - 15:00LT), the average concentration was a very high 50 ppb. Similarly to O 3 , the NOxconcentrations differ significantly between wet and dry seasons, due to biomass burningemissions. The average concentration for the wet season for NO was 0.23 ppb and NO 2 was0.69 ppb, while for the dry season NO averaged at 0.04 ppb and NO 2 at 2.73 ppb. Typicallevels of CO in the Amazon basin in the wet season were 150 ppb, with maximum values ofaround 500 ppb. In the dry season, peaks of 2,000 ppb in the daytime and 8,000 ppb at thenighttime were observed, associated with high black carbon and aerosol loadings. Thebiomass burning signal is very strong in Rondônia and moderate in Santarem.(Research project financed by FAPESP, CNPq and NASA).