Diurnal cycle of summer precipitation over the North China Plain and associated land–atmosphere interactions: Evaluation of ERA5 and MERRA‐2

Abstract

AbstractThe diurnal cycle of precipitation is influenced by the dynamic and thermodynamic processes of the land–atmosphere system and is a gateway for understanding land–atmosphere interactions. Here, we use satellite‐based precipitation data from CMORPH and TRMM 3B42 to evaluate the ability of ERA5 and MERRA‐2 reanalyses to depict the diurnal cycle of summer precipitation over the North China Plain (NCP). The observed diurnal cycles generally have a peak time in the afternoon or in the night to early morning, depending on the region. Both ERA5 and MERRA‐2 can reproduce the observed night to early morning precipitation peak, but the observed afternoon precipitation peak is only shown in ERA5. Moisture flux convergence is the main driver for night and early morning precipitation, while local land surface evapotranspiration and moisture flux convergence jointly drive afternoon rainfall. Compared with ERA5, the land surface is more strongly coupled with the atmosphere in MERRA‐2, and MERRA‐2 precipitation is more sensitive to precipitable water. The low‐level wind field is more divergent in MERRA‐2 than in ERA5 during afternoon, which causes weaker ascending motions, less precipitable water, and lower precipitation efficiency. The less favourable atmospheric conditions for precipitation, exacerbated by the strong land–atmosphere coupling, lead to the absence of afternoon rainfall in MERRA‐2.