Impacts of land surface processes on summer extreme precipitation in Eastern China: Insights from CWRF simulations

Understanding the impacts of land surface processes on summer extreme precipitation is crucial for accurate climate predictions. This study investigated these impacts across three subregions of eastern China (North China, Central China, and South China) using the regional Climate-Weather Research and Forecasting model with two land surface parameterization schemes: the Conjunctive Surface-Subsurface Process (CSSP) scheme and the NOAH Land Surface Model (NOAH). When compared with observational and reanalysis data, both schemes were found to successfully reproduce the spatial distribution of extreme precipitation, with the CSSP scheme showing distinct advantages in simulating evapotranspiration. The influence of land surface processes on summer extreme precipitation varies among the three subregions, largely depending on soil moisture conditions. In North China, a transitional zone between arid and humid regions, soil moisture primarily influences extreme precipitation, with biases arising from difference between the lifting condensation level and the planetary boundary layer height. In Central China, where soil moisture is moderate, soil moisture and net radiation jointly influence extreme precipitation, with biases linked to the planetary boundary layer height. In South China, where soil moisture is mostly saturated during summer, net radiation dominates the variability of land surface variables, with latent heat bias leading to extreme precipitation bias. Overall, soil moisture affects extreme precipitation by altering the energy and stability of the planetary boundary layer and the lifting condensation level. These findings could inform the assessment and future improvement of models, and support the monitoring and predicting of extreme precipitation events.