Aerosol impacts on deep convective clouds by acting as CCN and IN in regional climate model WRF-CAM5

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Thursday, 6 February 2014: 2:30 PM
Room C207 (The Georgia World Congress Center )
Kyo-Sun Sunny Lim, PNNL, Richland, WA; and J. Fan, L. R. Leung, C. Zhao, P. L. Ma, B. Singh, and G. J. Zhang

The Zhang and McFarlane (ZM) convection scheme (Zhang and McFarlane, 1995), incorporated with microphysics (Song and Zhang 2011), allows us to simulate the influence of aerosols in microphysical and dynamical processes for convective clouds in regional and global climate model frameworks by linking aerosols with cloud droplet activation and ice nucleation processes. Lim et al. (2013) implemented this new ZM convection scheme into the WRF model, coupled with the physics and aerosol packages from the Community Atmospheric model (CAM5) (Ma et al. 2013). The simulated precipitation and radiative properties with the new ZM scheme that includes microphysical processes show better agreement with the observed properties relative to the original ZM scheme. Analysis of the simulations suggests that increased detrained cloud water and ice with the new ZM scheme is responsible for the improved simulation skills. Further improvements in ice nucleation parameterizations have been added to the new ZM convection scheme for a consistent treatment of ice formation mechanism as used in the Morrison and Gettelman microphysics scheme that represents grid-scale processes and to avoid a possible double counting of ice freezing processes. Very recent ice nucleation parameterizations are also evaluated for mixed-phase clouds with observations. Detailed analysis of aerosol impacts through acting as CCN and IN in a regional climate simulation will be presented.