7.4    Simulated Carbonaceous and Inorganic Aerosols and their Effect on Radiation During the CalNex and CARES Campaigns in California

Fast, Jerome, Vinoj Velu, Ying Liu, and Manish Shrivastava, Pacific Northwest National Laboratory

The WRF-Chem model is used to simulate the evolution of carbonaceous and inorganic aerosols and their impact on radiation during May and June of 2010 over California when two field campaigns took place (CalNex and CARES).  We have merged the CalNex and CARES data into a common dataset for the Aerosol Modeling Testbed, which is supplemented with operational data from various networks.  The resulting rich dataset is used to evaluate how well the model simulates aerosol properties needed to understand uncertainties that could affect regional variations in radiative forcing.  The model reproduced many of the diurnal, multi-day, and spatial variations of aerosols as seen in the measurements; however, performance varied over California and some aerosol species are better represented than others.  The simulated backscatter and extinction compared well to observed profiles from the High Spectral Resolution Lidar, although the values in the boundary layer were too high at times and free tropospheric values were consistently higher than observed suggesting that long-range transport was too large.  Consistent with the Lidar comparisons, simulated aerosol optical depth was often too high.  Finally, the impact of the simulated aerosols on radiation will be quantified in relation to the uncertainties in predicted aerosol properties.