Extreme precipitation changes over the Yangtze River Basin in 1901-2020

To better understand the characteristics of long-term change and variability in regional extreme precipitation and to examine possible regional responses to global climate warming, we analyzed temporal and spatial patterns of precipitation and extreme precipitation index changes in the Yangtze River Basin (YRB) over the last 120 yr. Based on the China Meteorological Administration's daily precipitation data set of 60 city stations in mainland China from 1901-2020, we found that total annual precipitation and daily precipitation intensity of the Upper Reaches (UR) experienced a downward trend, but those of the Middle and Lower Reaches (MLR) showed an upward trend. Precipitation amount and intensity increased, while the number of precipitation days slightly decreased over the YRB during 1901-2020. Most extreme precipitation indices showed a decreasing trend in the first 60 yr that reversed after 1961 into slightly upward trends, except for consecutive dry days and wet days in the YRB during 1901-2020. There were significant downward trends for consecutive dry days and maximum 1 and 5 d precipitation during the first 60 yr, and significant upward trends for maximum 1 d precipitation, total extreme heavy precipitation, and very heavy precipitation days in the last 60 yr. The trends for extreme precipitation in the UR were lower than those in the MLR during 1901-2020, particularly in the last 60 yr, whereas the trends in the UR were higher than those in the MLR during 1901-1960. The fluctuations of extreme precipitation indices in the UR were more dramatic than those in the MLR, and the extreme precipitation indices all showed 5-10 or 20 yr periodic variabilities. The analysis also showed that observed changes in regional extreme events were directly related to rapid urbanization around the stations and multi-decadal variability of the East Asian monsoon.