Estudo da variabilidade sazonal da profundidade óptica do aerossol em São Paulo a partir de radiômetros MFRSR / Study of the seasonal variability of the aerosol optical depth in São Paulo using MFRSR radiometers.

AUTOR(ES)

André Cozza Sayão

DATA DE PUBLICAÇÃO

2008

RESUMO

The evaluation of the aerosol effects to the local and global radiation budget, as well as the impact on human health, particularly in large urban centers, demands knowing accurately their concentration and spatial-temporal distribution. In this context, the accurate long term monitoring from ground based stations installed around the world has become a challenge and a necessity for various areas of knowledge. Classically, the stations use the technique of Sun photometry to infer the concentration and size distribution of aerosols through the aerosol optical depth (AOD) and Ångström coefficient . In this paper we suggest a methodology to estimate AOD and Ångström coefficient through four channels of Multi-Filter Rotating Shadowband Radiometers (MFRSR) operating in Sao Paulo since 1999. These estimates were compared to the results of the AErosol RObotic NETwork (AERONET) between the years of 2004 to 2006. The results showed that the MFRSR can represent well the temporal variability of the AOD, but systematic differences were found with mean values of about 0.03 in AOD, in three of the four analyzed channels. The value suggested by WMO for clean air is at most 0.02. This result indicates that the methodology employed in MFRSR provides values of quality good. Also in this study, meteorological influences on the aerosol optical properties were analyzed. The meteorological variables were monitored at the Meteorological Station of the IAG-USP There was a linear relationship between Ångström coefficient and relative humidity (RH), indicating a growth of the average size of aerosols within a group with 0.20

ASSUNTO(S)

sun photometry optical depth urban pollution aerosols fotometria solar radiative processes in the atmosphere poluição urbana aerossóis profundidade óptica processos radiativos na atmosfera remote sensing sensoriamento remoto

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