Simulation of summer climate over East China by convection-permitting regional air-sea coupled model

In this research, the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Model was utilized to study the summer climate over eastern China and its adjacent ocean from 2009 to 2018. The COAWST model, equipped with a convection-permitting resolution of approximately 4 km for both atmosphere and ocean model, effectively replicated the patterns of precipitation for both land and ocean, including sub-daily extreme precipitation, and the diurnal cycle. The COAWST model offers accurate simulations of the land-sea contrast in terms of the diurnal cycle of precipitation, showing the peaks of rainfall over land and sea in the afternoon and morning respectively. The model exhibited higher skill in extreme precipitation intensity over the ocean, while it was more skillful in wet frequency over the land. Overestimation of land precipitation may be due to the combined effects of higher wind speeds (similar to 0.6 m/s higher over the ocean) from the atmospheric model and the elevated sea surface temperatures (about 0.8 degrees C warmer) from the ocean model, which may have influenced sea surface evaporation, increased latent heat release, and consequently increased precipitation. The significant topographical effects at the convective permitting resolution may have intensified land precipitation.