THE 1985 BIOMASS BURNING SEASON IN SOUTH-AMERICA - SATELLITE REMOTE-SENSING OF FIRES, SMOKE, AND REGIONAL RADIATIVE ENERGY BUDGETS

Using satellite imagery, more than five million square kilometers of t he forest and cerrado regions over South America are extensively studi ed to monitor fires and smoke during the 1985 biomass burning season. The results are characterized for four major ecosystems, namely, 1) tr opical rain forest, 2) tropical broadleaf seasonal, 3) savanna/grass a nd seasonal woods (SGW, and 4) mild/warm/hot grass/shrub (MGS). The sp atial and temporal distribution of fires are examined from two differe nt methods using the multispectral Advanced Very High Resolution Radio meter Local Area Coverage data. Using collocated measurements from the instantaneous scanner Earth Radiation Budget Experiment data, the dir ect regional radiative forcing of biomass burning aerosols is computed . The results show that more than 70% of the fires occur in the MGS an d SGW ecosystems due to agricultural practices. The smoke generated fr om biomass burning has negative instantaneous net radiative forcing va lues for all four major ecosystems within South America. The smoke fou nd directly over the fires has mean net radiative forcing values rangi ng from -25.6 to -33.9 W m(-2). These results confirm that the regiona l net radiative impact of biomass burning is one of cooling. The spect ral and broadband properties for clear-sky and smoke regions are also presented that could be used as input and/or validation for other stud ies attempting to model the impact of aerosols on the earth-atmosphere system. These results have important applications for future instrume nts from the Earth Observing System (EOS) program. Specifically, the c ombination of the Visible Infrared Scanner and Clouds and the Earth's Radiant Energy System (CERES) instruments from the Tropical Rainfall M easuring Mission and the combination of Moderate Resolution Imaging Sp ectrometer and CERES instruments from the EOS morning crossing mission could provide reliable estimates of the direct radiative forcing of a erosols on a global scale, thereby reducing the uncertainties in curre nt global aerosol radiative forcing values.