Radiative Forcing Effects Due to Black Carbon and Dust in the Atmosphere and Snow in the Western United States

Monday, 15 December 2014
Yuhao Mao1,2, Qinbin Li1,3, Kuo-Nan Liou1,3, Hong Liao2, Yu Gu1,3, Cenlin He1,3 and Li Zhang4, (1)Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, United States, (2)State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, (3)Joint Institute for Regional Earth System Science and Engineering, University of California, Los Angeles, CA, United States, (4)Department of Mechanical Engineering, University of Colorado, Boulder, CO, United States
BC and dust are two of the most important light absorbing aerosols in the atmosphere and thus have significant direct radiative forcing and snow albedo effects regionally. There are large uncertainties in the estimates of direct radiative forcing of BC and dust, which range from 0.2 to 0.9 W m-2 for BC (Bond et al., 2013) and 0.07 to 0.31 W m-2 in the long waves for dust (IPCC, 2007). BC and dust deposited on snow can significantly reduce the surface albedos and further affect the regional hydrological cycle. In the western U.S. (WUS), mountain snowmelt accounts for over 70% of the annual fresh water supply, which is facing severe challenges in the region recently. Transpacific transport of Asian emissions is likely becoming an even larger contributor to the fine particulate matter in the WUS in spring, as the Asian emissions are increasing under the rapid economic development in this region. We thus intend to better understand the radiative forcing effects of BC and dust in the atmosphere and snow in the WUS using an offline coupled 3-D global chemical transport model with a radiative transfer model. With improved dust and BC emissions and dust particle size distributions, we would like to quantify the relative contributions from different sources and source regions to the radiative forcing of BC and dust.