Half-day (daytime and nighttime) precipitation extremes in China: Changes and attribution from 1981 to 2022

Increased atmospheric water vapor pressure due to the warming climate has led to more frequent and extreme precipitation events, which has resulted in incalculable losses. The hydrothermal circulation suggests that extreme daytime and nighttime precipitation patterns can have many distinct consequences,ranging from changes in various scale hydrological cycles to social security concerns. However, the spatio-temporal patterns of daytime and nighttime precipitation events remain underexplored, lacking quantitative analysis. Therefore, our study analyzed daily precipitation data (including 24-h, daytime, and nighttime) from 1981 to 2022 across China to investigate extreme precipitation patterns at a half-day scale (daytime and nighttime). Fourteen monthly extreme indices associated with atmospheric circulations and sea surface temperatures were examined to clarify precipitation distribution patterns using random forest and optimal fingerprinting techniques. The main findings are: (1) A clear upward trend was found in cumulative precipitation, intensifying the frequency of extreme precipitation events. Notably, the increase in both accumulated 24-h precipitation and the rate of nighttime precipitation exceeded the rate of daytime precipitation between 1981 and 2022. This trend became more pronounced as precipitation events became more extreme. (2) Most regions in China exhibited an increasing trend in both cumulative precipitation days and total precipitation, particularly in the North China Plain, although the Yunnan-Guizhou Plateau saw significant decreases in both variables. (3) Extreme precipitation events were primarily driven by changes in the different types of the Subtropical High (Western Pacific, South China Sea, and Northern Hemisphere Subtropical High), along with the typhoons southeast of the Hu Huanyong line. These findings enhance the understanding of hydrothermal exchange processes and extreme precipitation, providing a useful basis for climate change adaptations in China.