Variations Of Water Vapor And Aerosol At The Brazilian Northeast Based On Modis Data

Abstract

The MODIS (Moderate Resolution Imaging Spectroradiometer) is the main instrument on board of the Terra satellite; project EOS (Earth Observing System)of the NASA, which was launched in December 1999. The present study analyzes the variations of aerosol and water vapor at the Northeast (NE) of Brazil (semiarid region), based on the data of the Terra platform between years 2000 and 2008. The monthly and annual averages of aerosol optical depth (AOD) and water vapor are presented above the seasonal variations (rainy and dry seasons) in urban and rural areas. It is used daily data of MODIS based on Terra platform, product MDOD08, obtained in GIOVANNI site. In the case of AOD, the monthly averages are obtained considering a preset sample of 5 days in every month, despising the pixels with negative values or without information, what differs from the monthly average presented by the Terra platform. In the case of the water vapor the same averages of the Terra platform are used. The rainy seasons in the area is diversified prevailing from February to May. The AOD in the region, is not homogeneous, it presents values in some pixels 30 or 40 times larger than in others and the standard deviation is very high. In the dry seasons medium AOD is three times larger than in the rainy seasons and systematically it presents extreme values, larger than one, in several pixels. The urban areas present larger AOD than the rural ones indicating anthropogenic emission.