5B.5 Representing aerosol effects in cumulus physics parameterization in WRF

Lim, Kyo-Sun Sunny, Jiwen Fan, Ruby Leung, Po-Lun Ma, Balwinder Singh, Pacific Northwest National Laboratory, and Guang Zhang, Scripps Institute of Oceanography

As demonstrated by observational and modeling studies, aerosols can exert significant influence on convection, with the potential to alter the timing and intensity of precipitation as well as provide feedbacks on the large-scale circulation. However, cumulus parameterizations used in climate simulations generally do not include cloud microphysics so aerosol-cumulus cloud interactions are not fully represented to allow investigation of aerosol effects on convection. Recently, Song and Zhang (2011) have developed an efficient two-moment microphysics parameterization scheme for convective clouds, which was implemented in the Zhang and McFarlane (ZM) convection scheme (Zhang and McFarlane 1995). This microphysics scheme explicitly treats the mass mixing ratio and number concentration of four hydrometeor species (cloud water, cloud ice, rain and snow), and describes several microphysical process based on Morrison and Gettelman (2008) with modifications to suit convective clouds. The new ZM convection scheme, which incorporates with microphysics, allows us to simulate the influence of aerosols on microphysical and dynamical processes for convective clouds in regional and global climate modeling frameworks. We have implemented the new ZM convection scheme into the Weather Research and Forecasting (WRF) model coupled with the physics package from the most recent version of the Community Atmospheric model (CAM5), which is newly implemented at PNNL (Ma et al. 2013). Simulations are being conducted over China to examine the impacts of the new scheme in simulating cloud properties, vertical mass fluxes, and precipitation compared with the original ZM scheme and to assess the significance of aerosol indirect effects from cumulus clouds at the regional scale. Model evaluation and analysis will be presented for selected case studies.