珠江流域非平稳性降雨极值时空变化特征及其成因

Spatiotemporal variations and the causes of non-stationary extreme precipitation in the Pearl River basin

受全球气候变化和人类活动影响,珠江流域极端降雨事件发生的频次和强度均发生变化,变化环境导致极端降雨样本存在非平稳性。本文以珠江流域43个站点1960—2012年的日降雨数据为基础资料,通过分析广义帕累托分布(GPD)的参数时变特性及其空间分布规律,探索珠江流域非平稳性极端降雨的时空变化特征及其成因。结果表明:珠江流域极端降雨序列的极值指数呈从东到西逐渐减小特点,表征强降雨之间的相关性由东向西减弱;极端降雨变化程度大的区域其变化程度呈减弱趋势,而变化程度小的区域其变化程度呈加强趋势;珠江三角洲和东江流域南部、柳江流域东北部地区50/100年一遇的日降雨量级较大,而南盘江西部地区则较小。7个影响因子中,厄尔尼诺指标(SMEI)对流域的极端降雨影响最明显。非平稳时变超定量(POT)模型与平稳POT模型的结果比较表明,本文提出的时变POT模型较好地处理了珠江流域部分区域降雨存在的非平稳性特征。

Due to global climate change and the growing impact of human activity, frequency and intensity of extreme precipitation events in the Pearl River basin are changed, and the consistency of non-stationary extreme precipitation no longer be guaranteed under changing environment. This paper attempts to explore the spatiotemporal variations and the causes of non-stationary extreme precipitation using time-varying Gen- eralized Pareto distribution （GPD） based on daily rainfall of 43 sites during 1960-2012 in the Pearl River basin. The results show that the extreme value index of extreme precipitation sequence decreases gradually from east to west, which indicates that the correlations of the extreme precipitations reduce from east to west. The region with large variationof extreme precipitation at present tends to weaken, and on the con- trary, the region with small variation of extreme precipitation at present tends to strengthen. The amount of 50- and 100-years return period daily precipitation in the Pearl River delta, the southern of the Dongjiang River basin and the northeastern of Liujiang River basin is greater than that in the western region of the Nanpan River basin. The SME index of ENSO is the most significant factor of extreme precipitation among the 7 factors. The comparative result of the time varying POT model and stationary POT model shows that the time varying POT model of non-stationary proposed in this paper can better overcome the problem of non-stationarv characteristics in harts of the study basin.