Analysis of Biomass Burning Aerosol Impacts on Clouds and Precipitation over Amazonia

Biomass burning aerosols are thought to have significant impacts on clouds and precipitation, yet little quantification of the effects has been performed. We employ a high-resolution nested computer model, together with satellite and in situ data, to analyze aerosol effects for the period between September 14th, 2006 and September 24th, 2006, during the peak of the biomass burning season. Consistent with previous studies, the satellite data show correlations between aerosol and cloud parameters, yet this study also demonstrates causation of these aerosol effects through modeling. High resolution biomass burning emissions data are gathered from the new Global Fire Emissions Database (GFEDv2), combined with land cover data and biomass burning emission factors. Three high-resolution domains (each nested within three increasingly coarser domains), two located over the central and southern Amazon, and the third located over the Atlantic Ocean in the exit region to the southeast, are used to track the evolution of the biomass burning plume, and the resulting aerosol effects on clouds and precipitation. Initial comparisons of in situ meteorological data with model data show good agreement in time and space. The impact of aerosols on cloud optical thickness, cloud liquid water/ice content, cloud top pressure, cloud fraction, and precipitation are illustrated through differences between simulations that include and exclude biomass burning emissions.