Analysis of spatial and temporal evolution characteristics of extreme precipitation in Chengdu area from 1960 to 2019

Based on daily precipitation data from 21 national ground meteorological observation stations in and around Chengdu City from 1960 to 2019, through constructing an extreme precipitation index system, the trend free pre-whitening Mann-Kendall (TFPW-MK) method and empirical orthogonal function (EOF) method were used to analyze spatial and temporal evolution characteristics of extreme precipitation in Chengdu area in the past 60 years from the perspective of time-history and spatial changes. Results indicate that extreme precipitation in Chengdu area showed a decreasing trend, especially demonstrated by indexes of wet-day precipitation and heavy precipitation. This feature is significantly different from extreme precipitation variation in urbanization areas in southwestern and southern China. Different extreme precipitation indexes have similar distribution modes in Chengdu area, including the modes of north-south type, west-east type, and radiation type. The north-south type is the main distribution mode, and the center of extreme precipitation gradually shifted from northern parts of Chengdu area in the 1960s to the south and southeast after 2000. The distribution modes of west-east type and radiation type reflect the impact of topography and urbanization on extreme precipitation in this area. The urbanization process has a certain precipitation enhancement effect in Chengdu area, the year 2005 was the abrupt change point of the precipitation enhancement effect, and after 2005, the probability and level of extreme precipitation in urban areas were higher than those in suburban areas, increasing the risk of urban flooding.