Climatic precipitation efficiency and its dependence on environmental factors over the Sichuan Basin and adjacent regions, Southwest China

Based on satellite observation and reanalysis data, basic features of cloud water and precipitation and the dependence of precipitation efficiency (PE) on environmental factors over the Sichuan Basin and adjacent regions are investigated. Results found that the spatiotemporal distribution characteristics of precipitation and cloud water over the Sichuan Basin and adjacent regions are consistent. The liquid water path (LWP) and ice water path (IWP) in the Sichuan Basin (SCB) are richer than the West Sichuan Plateau (WSP) and Yunnan-Guizhou Plateau (YGP), and the contribution of IWP to precipitation in Sichuan Basin and adjacent regions is greater than that of LWP. Furthermore, the results indicate that PE has the most significant dependence on the low-tropospheric relative humidity (RH) and the convective available potential energy (CAPE) over the Sichuan Basin and adjacent regions. Higher RH and CAPE contribute to a larger PE in the Sichuan Basin. The CAPE has a positive effect on the PE, which indicates that PE is directly affected by precipitation convection, mainly due to the special topography of the Sichuan Basin and adjacent regions, leading to frequent convective activities. The ratio of LWP to IWP (RLI) affects PE. The RLI decreases with the increase of IWP, leading to an increase in PE. RLI is negatively correlated with PE, which further indicates that ice water clouds have a more significant impact on PE over the Sichuan Basin and adjacent regions. Through this study, we can enhance our understanding of the formation processes, spatio-temporal structures, and evolutionary mechanisms of cloud precipitation in the Sichuan Basin and its adjacent areas. This is crucial for unraveling the dynamics of atmospheric water cycle, climate change processes, and optimizing the utilization efficiency of cloud water resources.