THE EFFECT OF SMOKE PARTICLES ON CLOUDS AND CLIMATE FORCING

Smoke particles from biomass burning can generate forcing of climate b y modifying cloud microphysics and reflectance of sunlight. Cloud modi fication, critical to an understanding of climate change, is uncertain and variable. Satellite data over the Amazon Basin and Cerrado were a nalyzed for cloud reflectance and droplet size and for smoke concentra tion. Smoke increased cloud reflectance from 0.35 to 0.35, while reduc ing droplet size from 14 to 9 micrometers. The regional variability of the smoke effect was correlated to the availability of water vapor. D uring the 3 months of biomass burning in the dry season, the smoke-clo ud forcing of climate was only -2 watts per square meter in this regio n, much smaller than what can be inferred from model predictions.