Temporal and spatial variation and non-stationary characteristics of extreme precipitation in the Shanmei reservoir basin
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Abstract:
The probability distribution of extreme precipitation in the Shanmei reservoir basin is expected to change due to the dual influence of global climate change and human activities,showing non-stationary characteristics.Therefore,investigating the temporal and spatial trend characteristics and the non-stationarity of the extreme precipitation are valuable for policy decisions. Based on the daily precipitation data of 8 meteorological stations in the Shanmei reservoir basin from 1972 to 2010,9 extreme precipitation indices including 6 intensity indices and 3 frequency indices were used to describe the extreme precipitation characteristics.The Pre-Whitening Mann-Kendall (P -WM-K) method was adopted to analyze the temporal and spatial trend changes of extreme precipitation,and the generalized additive models for location,scale,and shape (GAMLSS) was employed to characterize the non-stationarities in the 9 indices in the Shanmei reservoir basin. The number of moderate precipitation days (R10 mm) and the number of heavy rain days (R25mm) showed a downward trend while the number of very heavy rain days (R50mm) showed an upward trend with a 0.05 significant level.Except for the total precipitation (PRCPTOT),the other intensity indices (daily intensity (SDII),very wet day precipitation (R95P),extremely wet day precipitation (R99P),max 1-day precipitation (RX1day) and the max 5-day precipitation (RX5day) increased significantly.The linear trend rate of R95 reached 30.5 mm/（10 a）.The extreme precipitation indices had abrupt changes in the whole basin,and the mutation years mainly occurred in the late 1980s and early 1990s.In terms of spatial variation,R10mm and R25mm showed a download trend for all the stations,and reaches a 005 significant level in Dazhong and Zimei Stations.R25mm showed a downward trend for the stations in the exception of the Dongguan and Shanmei Stations while the trend was not significant.The R50mm and extreme precipitation intensity indices showed an upward trend in the southeastern part of the basin (Yongchun Station,Huyang Station,Dongguan Station,and Shanmei Station),and the trend was significant.The PRCPTOT had decreased significantly in the northwest of the basin.The GAMLSS model was fitted well to each precipitation station,and the Filliben coefficient passed the 0.05 significance level.R10mm and R25mm showed stationary characteristics.The R50mm showed non-stationary characteristics at 50% of the stations in the basin,and that was dominated by mean non-stationary.Except for PRCPTOT,the other intensity indices mainly showed non-stationary characteristics which mainly manifested as the mean non-stationary.Under the non-stationary conditions,the mean and variance of the extreme precipitation indices was mainly characterized by an increasing trend in the southeastern basin,and mainly showed a decreasing trend in the northwest. In light of climate variability and anthropogenic activities,the stable environment of extreme precipitation events in the Shanmei reservoir basin had been disturbed.The intensity of extreme precipitation and R50mm increased significantly in the Shanmei reservoir basin,especially in the southeastern part of the basin.This showed non-stationary characteristics in the study area.The intensity of extreme precipitations as well as uncertainty would increase,which may lead to more related disasters in the future.
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