Effects of the Physical Process Ensemble Technique on Simulation of Summer Precipitation over China

The e?ects of the physical process ensemble technique on simulation of summer precipitation over China have been studied by using a p-σ regional climate model with 9 vertical levels (pσ-RCM9). The results show that there are obvious di?erences among simulations of summer precipitation over China from different individual ensemble members. The simulated precipitation over China is sensitive to different cumulus convection, radiative transfer, and land surface process parameterizations. These di?erences lead to large uncertainties in the simulation results. The standard deviation of the simulated summer precipitation departure percentage over West China is larger than that over East China, signifying that the simulated precipitation over East China has higher reliability and consistency than that over West China. The Talagrand diagram shows that the ensemble system has reasonable dispersion in the simulated summer mean precipitation over East China. The summer ensemble mean precipitation over East China evaluated by various indices is better than most single simulations. The physical process ensemble technique reduces the uncertainties of the model physics in precipitation and improves the simulation results as a whole. Further,adopting the optimized ensemble mean method can obviously improve the performance of the pσ-RCM9 model in simulation of summer precipitation over East China.