资源环境科技发展态势分析平台

This study focuses on changing trends in the spatial variance and annual distribution of precipitation across mainland China during the period 1957-2014. The influence on precipitation of temperature, the East Asian summer monsoon (EASM), and related atmospheric circulation variables are examined to explore the underlying mechanisms driving the changes in precipitation. Statistically significant downward trends in the number of wet days were observed in humid regions. Large parts of southeastern China featured high temporal inequality of rainfall over the course of a year, with extreme precipitation events contributing a relatively large percentage of the total annual precipitation. Arid regions generally showed statistically significant upward trends in the number of wet days and in the fraction of extreme precipitation but a decrease in the temporal inequality. These spatial heterogeneities indicate that extreme precipitation became more widespread across mainland China. Temperature dominated the long-term changes in precipitation indices over large regions of mainland China, except in the Jianghuai region, where the weakening EASM induced greater precipitation and a more uneven annual distribution of precipitation. The effects of temperature on precipitation were region dependent and varied with precipitation intensity. This contributed to the overall decrease in the spatial variance of extreme precipitation and the increase in the temporal inequality of precipitation over eastern China. However, the EASM was more important for the interannual variability of precipitation indices over the west of northwestern China, the Yanghuai region, and some grids in southern China. The EASM exerted a zonal influence on precipitation variability through the modulation of water vapor patterns, wind fields, and convection activities.