1960—2019年关中平原极端降水时空变化及非平稳性分析

Spatial and temporal variation and non-stationary analysis of extreme precipitation in Guanzhong Plain from 1960 to 2019

【目的】为探究极端降水的时空变化及其非平稳性特征,【方法】选取位于关中平原范围内1960—2019年长时间降水序列,利用极点对称模态分解(ESMD)方法分析了区域极端降水的时间变化特征,并采用Sen斜率估计+Mann-Kendall(Sen+MK)方法对5d最大降水量(Rx5)进行空间分析,最后利用广义可加模型(GAMLSS)对极端降水序列的非平稳性特征进行分析。【结果】研究发现:在时间变化趋势上,持续湿润指数(CWD)、年降雨量(PRCPTOT)、5 d最大降水量(Rx5)呈现出先下降后上升的趋势,整体为下降趋势,极强降水量(R99P)和降水强度(SDII)呈上升趋势;大雨日数(R25)呈现出下降趋势;在空间分布上,其中春、秋两季下降明显,降雨主要集中在夏季,趋势系数最高达到0.17 a^(-1),冬季降雨有一定程度的增加;关中平原极端降水指数基本为平稳序列,个别站点非平稳性较为明显。【结论】关中平原极端降水量和不确定性变化较为稳定,未来突发性强降水事件出现概率较低,但是个别区域会遭到较为严重的灾害风险,研究结果可为将来关中平原相关洪涝预防措施提供一定指导。

[Objective]To investigate the spatial and temporal variability of extreme precipitation and its non-stationarity characteristics,[Methods]a long time precipitation series located within the Guanzhong Plain from 1960 to 2019 was selected,and the temporal variability characteristics of regional extreme precipitation were analysed using the pole symmetric modal decomposition(ESMD).Sen′s slope+Mann-Kendall(Sen+MK)was used for the 5-day maximum precipitation(Rx5)for spatial analysis.Finally the non-stationarity characteristics of the precipitation series were analysed using the generalised additive model(GAMLSS).[Results]The results show that:in terms of temporal trends,the continuous wet days(CWD),the total precipitation(PRCPTOT)and the maximum five-day precipitation(Rx5)showed a decreasing trend followed by an increasing trend,while the very heavy precipitation(R99P)and the extreme precipitation intensity index(SDII)showed an increasing trend;the number of heavy rainfall days(R25)showed a decreasing trend;in terms of spatial distribution,among which the decline was obvious in spring and autumn,with Rainfall is mainly concentrated in summer,with a trend coefficient of 0.17 a^(-1),and there is a certain degree of increase in winter rainfall;the extreme precipitation index in the Guanzhong Plain is basically a smooth series,with non-smoothness more obvious at individual stations.[Conclusion]The extreme precipitation and uncertainty variation in the Guanzhong Plain is relatively stable,and the probability of future unexpected heavy precipitation events is relatively low,but individual areas are subject to more severe disaster risk,and the results of the study may provide some guidance for future flood prevention measures related to the Guanzhong Plain.