Examining the Impact of Smoke Aerosol on Clouds and Precipitation using a Regional Model WRF-Chem-SMOKE and A-Train Data: A Case Study of Canadian Boreal Forest Wildfires in Summer 2007

In the summer of 2007, severe boreal forest fires occurred in Alaska and Canada. The A-Train satellite constellation provided a wealth of information on smoke aerosols, clouds, and precipitation. Using these data in conjunction with the WRF-Chem-SMOKE regional model, we examine how smoke affected the properties of mixed-phase clouds and related changes in precipitation. The size- and composition-resolved smoke fluxes were calculated by utilizing the WF_ABBA burned area data set and vegetation-dependent emission factors. Smoke is considered as a mixture of organic carbon, black carbon and sulfate particles. In the SMOKE module, CCN and IN are prognostically predicted from the modeled 3D smoke fields and then incorporated in cloud microphysics. We considered several scenarios of initial size distributions and emission factors to examine the sensitivity of 3D smoke fields to these parameters and associated changes in clouds and precipitation. The multi-satellite and multi-sensor products from A-Train (e.g., OMI, MODIS, CALIPSO) were used to evaluate the realism of modeled smoke spatiotemporal distribution. We examine changes in liquid and ice water content and profile, as well as changes in total precipitation and its spatial pattern. Several CloudSat passes were considered to evaluate simulated cloud properties against satellite observations.