Modeling the Impact of Amazonian Biomass Burning Aerosol on Clouds and Climate

Abstract:

Biomass burning aerosol (BBA) can alter clouds by microphysical processes (the indirect effect), and by absorbing shortwave radiation which subsequently alters temperature and stability profiles (the semi-direct effect), and thus cloud development. The magnitude and direction of the semi-direct effect from BBA is sensitive to many factors, including relative altitudes of cloud and BBA and the optical properties of BBA. During September 2012 the SAMBBA (South American Biomass Burning Analysis) field campaign took place, during which the UK BAe146 aircraft performed measurements of BBA and cloud properties over the Amazon. Properties of BBA were found to vary over different burning regimes (forest vs cerrado/tropical savannah), with single scattering albedo at 550nm being notably lower in the east over cerrado (<0.85) compared to in the west over forest burning fires (>0.9). We present results from the HadGEM3 climate model, where we vary the presence and optical properties of BBA emitted over the South American region to determine how sensitive regional climate and the atmospheric circulation are to BBA properties.