Spatio-temporal variations of precipitation extremes in Hanjiang River Basin, China, during 1960–2015

Abstract

Under the background of global warming, precipitation extremes are the main reasons for the cause of drought-flood disasters at local scales. Regional evaluations on the spatial and temporal variations of precipitation extremes are needed for comprehensively understanding the precipitation-related natural disasters. In this study, ten extreme precipitation indices from 17 meteorological stations in the Hanjiang River Basin, China, were computed and their spatial and temporal variations were analyzed using linear tendency method, based on daily precipitation data for the period of 1960–2015. Results indicated that consecutive dry days, number of heaviest  precipitation days, maximum 1-day precipitation, very wet day precipitation, extremely wet day precipitation, and simple precipitation intensity index exhibited non-significant increasing trends. Consecutive wet days, number of heavy  precipitation days, maximum 5-day precipitation, and total wet day precipitation exhibited non-significant decreasing trends. Using Mann-Kendall test, cumulative anomaly method, and moving t test for cross-validation, an abrupt increase was detected in 1978 for both very wet day precipitation and extremely wet day precipitation and for both these two indices, there were two significant periodic variation cycles, i.e., 1–2 years and 4 years, and in addition, extremely wet day precipitation had a change cycle of 8 years. The cross-wavelet transform method suggested that Pacific Decadal Oscillations and Sea Surface Temperature might be the two driving factors of extreme precipitation variation. The changing trends of precipitation extremes showed regional differences, but the stations with significant trends were not clustered. All the indices were highly correlated with each other, except for the number of consecutive dry days and consecutive wet days. The contribution of extreme precipitation to total precipitation revealed a non-significant increase in the study area. There were negative correlations between most of the indices and elevation with high level of significance. Changes of large-scale atmospheric circulation showed an increasing geopotential height and a weakened summer monsoon and had an impact on the variations of extreme precipitation.