@Article{HolbenSetEckPerSlu:1996:EfDrSe,
               author = "Holben, B. N. and Setzer, Alberto Waingort and Eck, T. F. and 
                         Pereira, Alfredo and Slutsker, I.",
          affiliation = "NASA/Goddard Space Flight Center, Greenbelt, MD, United States and 
                         Instituto Nacional de Pesquisas Espaciais, Centro de Previs{\~a}o 
                         do Tempo e Estudos Clim{\'a}ticos (INPE.CPTEC) and Hughes STX 
                         Corporation, NASA/Goddard Space Flight Center, Greenbelt, MD, 
                         United States and Instituto Nacional de Pesquisas Espaciais, 
                         Centro de Previs{\~a}o do Tempo e Estudos Clim{\'a}ticos 
                         (INPE.CPTEC) and Sci. Systems and Applications, Inc., NASA/Goddard 
                         Space Flight Center, Greenbelt, MD, United States",
                title = "Effect of dry season biomass burning on Amazon Basin aerosol 
                         concentrations and optical properties, 1992-94",
              journal = "Journal of Geophysical Research: Atmospheres",
                 year = "1996",
               volume = "101",
               number = "D 14",
                pages = "19465 - 19481",
                month = "Aug.",
             keywords = "aerosol, biomass burning, dry season, optical thickness, 
                         stratosphere, Brazil, Amazonia.",
             abstract = "Aerosol concentrations and properties have been derived from a 
                         network of ground-based Sun-sky radiometer measurements in 
                         Brazil's Amazon basin region since 1992. The measurements 
                         characterize the background aerosol environment and aerosol 
                         emissions from biomass burning at eight selected sites. The 
                         duration and frequency of the measurements provide the foundation 
                         of an aerosol climatology based on direct sun measurements of 
                         aerosol optical thickness and retrievals of size distribution from 
                         solar aureole measurements. The aerosol optical thickness 
                         measurements clearly illustrate that for sites located within 
                         regions of biomass burning the duration of smoke above background 
                         levels often exceeds 2 months and frequently at levels an order of 
                         magnitude above background. The aerosol optical thickness range 
                         during preburning conditions was 0.11 to 0.27 at 440 nm. Under 
                         these conditions, stratospheric aerosols from Pinatubo constituted 
                         a significant part of the signal in 1993 but were about 50% less 
                         in 1994. During the burning season; smoke elevated the aerosol 
                         optical thickness above 1.0 for seasonally averaged values 
                         measured at 440 nm at sites located in active source regions in 
                         Mate Grosso, Rondonia, and Tocantins states. The measurement sites 
                         are located in the cerrado and forest conversion areas. Analysis 
                         of the size distribution of the particles indicated that the 
                         increase in aerosol optical thickness was associated with an 
                         increase of an accumulation and coarse particle modes. The 
                         asymmetry factor ''g'', computed from the phase function, showed 
                         considerable spectral dependence between the preburning and 
                         burning seasonal phases. The 1020-nm channel was reduced from 0.66 
                         to similar to 0.53, while at 440 nm little seasonal phase 
                         variation was noted. Conditions of burning were sufficiently 
                         strong that the atmospheric conditions associated with the 
                         climatological definition of a dry season was subdivided into (1) 
                         preburning, (2) transition to burning, (3) burning, and (4) 
                         transition to wet season phases for most sites. Averages and 
                         frequency distributions were used to characterize each seasonal 
                         phase by site. Changes in total column water vapor amount, also 
                         retrieved from direct sun measurements, did not have an apparent 
                         effect on the optical properties of the aerosols.",
           copyholder = "SID/SCD",
                 issn = "0102-261X",
             language = "en",
        urlaccessdate = "08 maio 2024"
}