Interdecadal Variation of Temporal Inhomogeneity and Precipitation Structure Changes of the Autumn Rain of West China

In this paper homogenized daily precipitation data from 335 meteorological stations in western China from 1971 to 2022 are used to calculate each station"s Precipitation Concentration Index (CI). By combining the regional averaged rainfall intensity, number of rainfall days, and the proportion of different intensity rainfall days, along with statistical methods such as moving averages and the Piecewise Linear Fitting Model (PLFIM), the study analyzed changes in the precipitation structure and the uneven distribution of the Autumn Rain of West China. The results revealed the following: (1) Most stations in the western China region have a multi-year average CI exceeding 0.6 during the autumn rain period, suggesting that precipitation is not evenly distributed over time at many stations. Further comparative analysis of specific years and stations supports the validity of the CI. (2) Over the past decade, the temporal inhomogeneity of the Autumn Rain of West China has been gradually intensifying. The direct cause is the shift in precipitation structure over the past 20 years, characterized by a decrease in the proportion of light rain and an increase in the proportion of heavy rain and extreme precipitation. The rise in intense rainfall has led to greater precipitation concentration, thereby enhancing the temporal inhomogeneity of precipitation distribution.