Modeling the transport and optical properties of smoke plumes from South American biomass burning

Abstract

This study investigates the transport and optical properties of smoke plumes from South American biomass burning by using an aerosol transport and microphysical model. In general, the model can reproduce the smoke aerosol optical properties observed by satellite and ground‐based instruments during the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia ‐ Smoke Aerosols, Clouds, Rainfall and Climate (LBA‐SMOCC) campaign. The simulated spatial distribution of smoke aerosol loading over South America also compares well to satellite observations, suggesting that the transport processes in the model are adequate over this region. The results further suggest that the emissions provided by version 2 of the Global Fire Emissions Database are too low over South America. However, wet deposition may be too aggressive in the model. Since the model wet deposition does not include the feedback smoke may have on cloud formation and precipitation suppression, too many aerosols may be removed. Surprisingly, given the different vegetation types, the model simulations also suggest that similar initial particle size distributions and aerosol optical properties can be used to simulate smoke from both African savanna and South American forest fires. However, to reproduce the observed smoke aerosol optical properties over South America, humidification of smoke aerosols needs to be considered. Model results and observations both suggest that the typical single scattering albedo of smoke over South America and Africa differ because of relative humidity, not vegetation type. Overall, this work suggests strategies for improved treatment of South American smoke plumes in climate and microphysical models.