Effects of Different Land‐Surface Schemes on the Simulation of a Heavy Rainfall Event by WRF

Abstract

AbstractA heavy rainfall event occurring in the Yangtze‐Huaihe valley and south China during late June, 2003 was simulated to examine the effects of different land‐surface schemes on simulated precipitations using the Weather Research and Forecasting Model (WRF) Version 3.1 and National Centers for Environmental Prediction (NCEP) analysis data. The simulation was performed in the short‐range mode for 24‐h integrations. The results show that generally the simulated heavy rainfall event is sensitive to different land‐surface schemes, the scheme‐induced difference of threat score becomes larger as the forecast categories of rainfall gets higher within the relatively large study subarea, where the scheme‐induced relative differences of precipitation can amount up to 30% with an average of 7%, while the maximum values of daily precipitation differences can be as large as 100%~150%, and different schemes lead to simulated systematic differences in averaged sensible and latent heat fluxes that are characterized by regional distributions. Finally, the land‐surface schemes can substantially affect the simulated precipitations via two mechanisms, i.e., by affecting land surface evaporation, and by affecting low‐level atmospheric circulation and water vapor convergence, the schemes exert great influences, respectively, on the simulated rainfall over a relatively large area of the model domain (e.g., with an average difference of 7% and a maximum difference of ~30%), and on simulated heavy rainfalls within small areas including rainfall centers (e.g., up to differences within 100%~150%). All these suggest that different land surfaces affect heavy rainfall weather at different spatial scales and to different extents, and that improving the land‐surface schemes can lead to better simulation of the heavy‐rainfall weather with the WRF model.