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RESUMOEstudos relacionados às propriedades óticas de aerossóis atmosféricos são de grande relevância para a pesquisa. Desta forma, o presente trabalho propõe uma caracterização sazonal e interanual da Profundidade Ótica de Aerossóis (AOD) na faixa de 500 nm para uma região de transição Pantanalcerrado (Características de Cerrado), na região centro sul no estado de Mato Grosso. Os dados de AOD 500 nm foram adquiridos junto à rede AERONET de 2001 a 2013. Seus valores diários apresentam claramente um comportamento sazonal com mínimos nas estações chuvosas e máximos na estação seca. Os primeiros ficaram concentrados em aproximadamente 0,2, enquanto que os máximos atingiram valores próximos a 3,0. Com relação à caracterização interanual, percebeu-se que não há comportamento periódico, havendo grandes variações de ano para ano. As médias mensais de AOD 500 nm foram correlacionadas com os registros mensais de focos de queimada para o estado de Mato Grosso, no entanto, não houve correlação estatisticamente significativa, o que evidencia que tal relação existe, mas que não é direta. Palavras -chave: AERONET. Queima de Biomassa. Depressão Cuiabana. ABSTRACTStudies related to the optical properties of atmospheric aerosols are of great relevance for research. Thus , this paper proposes a seasonal and inter-depth characterization of Aerosol Optical Depth (AOD) in the range of 500 nm for a Pantanal -Cerrado transition region (Characteristics of Cerrado) , in the central south region in the state of Mato Grosso. The AOD 500 nm data were acquired from AERONET network from 2001 to 2013. The AOD 500 nm daily values present a seasonal pattern with minimum and maximum in the rainy and dry seasons, respectively. The minimum values were concentrated approximately at 0.2 whereas the maximum values close to 3.0. Regarding the inter-annual characterization, it was noticed that not a periodic behavior, with large variations from year to year. The monthly averages of AOD 500 nm were correlated with the

The aerosol radiative effect is an important source of uncertainty in estimating the anthropogenic impact of global climate change. One of the main open questions is the role of radiation absorption by aerosols and its relation to land use worldwide, particularly in the Amazon Rainforest. Using AERONET (Aerosol Robotic Network) long-term measurements of aerosol optical depth (AOD) at a wavelength of 500 nm and absorption AOD (AAOD) at wavelengths of 440, 675, and 870 nm, we estimated the fraction and seasonality of the black carbon (BC) and brown carbon (BrC) contributions to absorption at 440 nm. This was conducted at six Amazonian sites, from central Amazon (Manaus and the Amazon Tall Tower Observatory—ATTO) to the deforestation arc (Rio Branco, Cuiabá, Ji-Paraná, and Alta Floresta). In addition, land use and cover data from the MapBiomas collection 6.0 was used to access the land transformation from forest to agricultural areas on each site. The results showed, for the first time, important geographical and seasonal variability in the aerosol optical properties, particularly the BC and BrC contributions. We observed a clear separation between dry and wet seasons, with BrC consistently accounting for an average of approximately 12% of the aerosol AAOD at 440 nm in the deforestation arc. In central Amazon, the contribution of BrC was approximately 25%. A direct relationship between the reduction in forests and the increase in the area dedicated to agriculture was detected. Moreover, places with lower fractions of forest had a smaller fraction of BrC, and regions with higher fractions of agricultural areas presented higher fractions of BC. Therefore, significant changes in AOD and AAOD are likely related to land-use transformations and biomass burning emissions, mainly during the dry season. The effects of land use change could introduce differences in the radiative balance in the different Amazonian regions. The analyses presented in this study allow a better understanding of the role of aerosol emissions from the Amazon Rainforest that could have global impacts.

Highlights • The columnar and surface aerosol optical properties were combined and analyzed. • A tenfold increase in the scattering coefficient is observed in the dry season. • AERONET SSA values were higher 8.4 ± 2.9% compared to the SSA from situ measurements. • A SWARF AERONET-SBDART regression analysis shows a high correlation. • SWARFTOA is observed to be-3.66 ± 1.59 W.m-2 in the wet season.