Another source of error in simulating or predicting Meiyu: a case study

The Meiyu phenomenon in the Yangtze River Basin (YRB) is a significant characteristic of summer precipitation in China. The successful prediction of Meiyu front intensity and location is highly important for disaster prevention and reduction. In this study, the Weather Research and Forecasting (WRF4.0) model was used to simulate the 2020 extreme Meiyu to find the possible sources of bias in simulating or predicting Meiyu. The results revealed that the simulated Meiyu rain band deviates from the YRB and lingers abnormally in South China from June 15 to July 6. This deviation is termed the “southern lingering bias (SLB)” in this paper. The SLB is closely associated with the excessive sensible heat over the Tibetan Plateau and the large positive latent heat flux bias over the South China Sea. Selecting an appropriate land surface model, surface layer scheme, or planetary boundary layer scheme can reduce the bias of simulated surface heat fluxes and improve Meiyu simulations. These findings can improve our understanding of the source of model bias and enhance the accuracy of Meiyu simulation or prediction via dynamical models.