Radiative Forcings of Wild Fire Aerosol and Impacts on North American Climate

Wednesday, May 14, 2014 - 07:00
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This study investigates the radiative forcings and climatic effects of aerosol particles emitted from wild fires with the Community Earth System Model version 1.2 (CESM1.2). The 4-mode version of modal aerosol module (MAM4) together with the daily Global Fire Emissions Database (GFED) version 3.1 for the period of 2003-2011 are used in the numerical experiments. We diagnose the direct, indirect, and surface albedo forcings by wild fire aerosols (black carbon (BC), organic matter (OM)) by conducting several experiments with and without fire aerosols. The fire BC-induced snow forcing is most significant during the springtime in Northeast Asia and Western United States. Surface warming by 1.5-2.0 K is found over these areas in spring due to the increased absorption of solar radiation at surface, while a cooling by about 1.5 K is observed in Canada. The fire BC-induced surface albedo effect generates a PNA (Pacific/North American) like teleconnection pattern during the spring with two anti-cyclones over the North Pacific and North Atlantic oceans and a trough in Canada. This pattern has significant impacts on North American precipitation. In summer, the indirect effect of fire OM dominates the fire aerosol effects in North America. The enhanced (more negative) shortwave cloud forcing, increased low-level clouds and cloud liquid water path due to fire OM are found in Canada, Alaska and North East Asia. Decreased surface air temperature and suppress of precipitation are also found in these regions.

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