Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Biomass Burning Aerosol Vertical Distribution Over the South African-Atlantic Region: Perspectives from Multi-Models and CALIOP

Friday, December 16, 2016 - 08:45
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Open burning of agricultural residue in the southwestern African Savanna during the austral spring season (July-October) contributes to about one-third of the global biomass burning (BB) emissions. The optically thick smoke aerosol plumes originating from this BB are transported primarily westward for thousands of kilometers by the mid-tropospheric trade winds. Unlike the smoke from industrial activity and biofuels that intermingles with clouds in most regions, the smoke here mainly overlies the vast stretches of marine stratocumulus clouds over the South-East Atlantic. Accurate simulations of the existence, location and properties of these BB aerosols are necessary to determine their effects on the underlying clouds and eventually on the regional climate. Towards this end, we evaluate the simulation of long-range transport and vertical distribution of BB aerosol by GEOS-5 (coupled to GOCART) over the complete south African-Atlantic region using CALIOP observations and compare the simulation with other global aerosol models participating in the AeroCom Phase-III BB experiment to find any common model biases. Most of the models exhibited some common features after long-range transport of aerosol plumes that were distinct from that of CALIOP. Most importantly, just off the western coast of the continent, the model simulated BB aerosol plumes rapidly descend to lower levels while CALIOP data suggest that smoke plumes continue their horizontal transport at elevated levels above the marine boundary layer. However, the levels to which the aerosol plumes get subsided and the steepness of their descent vary amongst the models and also amongst the different sub-regions of the domain, even though the fields driving the large-scale horizontal and vertical transport amongst the models were found to be similar. To reveal other possible cause(s) of differences between model and CALIOP, aerosol transport over the ocean was further investigated in the context of GEOS-5.

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