5B.7 Exploring the WRF simulation skill of Southeastern United States summer rainfall: sources of skills and the mechanisms

Li, Laifang, Wenhong Li, Duke University, and Jiming Jin, Utah State University

Regional climate simulation is important to understand the mechanisms and processes that control Southeastern (SE) United State (US) summer precipitation. However, accurately simulating SE US summer precipitation remains challenging. In this study, skills of SE US summer precipitation simulations at process levels was evaluated using the Weather Research and Forecasting (WRF) model driven by the Climate Forecast System Reanalysis (CFSR) data. Influences of parameterization schemes and model resolution on precipitation were investigated. Our results show that WRF simulations of SE US summer precipitation are most sensitive to the cumulus schemes embedded in WRF, moderately sensitive to the planetary boundary layer schemes, but less sensitive to the microphysics schemes. Among five WRF cumulus schemes analyzed, the Zhang-McFarlane scheme outperforms the other four in reproducing the observed precipitation amount and pattern due to its capability to represent the convective rainfall triggering processes over the SE US. The Zhang-McFarlane scheme simulated precipitation at 15-km resolution is also compared with the 3-km convective resolving simulation. The results indicate that 3-km simulation does not show advantages over the 15-km simulation. Thus, besides increasing model resolution, a realistic convective rainfall triggering scheme is important to obtaining satisfactory simulation skills in SE US summer precipitation.