A51I-0186
Aerosol-stratocumulus Interactions over the Southeast Pacific: A Process Study Using WRF-Chem

Friday, 18 December 2015
Poster Hall (Moscone South)
Yulu Qiu1,2, Guoxing Chen2, Wei-Chyung Wang2, Hong Liao1, Jen-Ping Chen3 and Huiwen Xue4, (1)State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, (2)Atmospheric Sciences Research Center, University at Albany, State University of New York, Albany, NY, United States, (3)Department of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan, (4)Department of Atmospheric and Oceanic Sciences, Peking University, Beijing, China
Abstract:
The recent WRF study by Chen et al. (2015) showed that the shortwave radiative forcing by the stratocumulus over the southeast Pacific (SEP) is much enhanced by anthropogenic aerosols from South America. Here we further investigate the aerosol-stratocumulus interactions on the process level using the WRF-Chem model which explicitly simulates the aerosol emissions and formations. Two cloud microphysics schemes are used: the widely-applied Lin scheme and the physics-based two-moment scheme used in Chen et al. (2015). The simulations with the Lin scheme captured some observed features of aerosols (e.g., aerosol mass and optical depth decreases westward along 20°S) and key aerosol-cloud microphysics interactions (e.g., more cloud droplet numbers near the coast). However, biases were also noticed, such as the overestimation of cloud droplet number near the coast, and the underestimation of aerosol concentration over the remote ocean. These could be caused by the inadequacy in cloud process parameterization, such as a lack of aerosol recycling from rain droplets in coupling with chemistry and microphysical modules (Saide et al, 2012). The two-moment scheme that explicitly addresses these processes is expected to minimize the biases. Detailed investigations of the cloud microphysics processes using the two schemes, and, to the extent possible, comparisons with observations will be presented and discussed.

Chen, G.-X., W.-C. Wang, and J.-P. Chen, 2015: Aerosol-stratocumulus-radiation interactions over Southeast Pacific. J. Atmos. Sci., 72, 2612-2621.

Saide, P. E. (and 16 co-authors), 2012: Evaluating WRF-Chem aerosol indirect effects in Southeast Pacific marine stratocumulus during VOCALS-REx, Atmos. Chem. Phys., 12, 3045–3064.