1970-2015年汉江流域多尺度极端降水时空变化特征

基于汉江流域63个气象站点逐日降水数据,辅以超阈值抽样、极端降水集中度（EPCD）和集中期（EPCP）、Mann-Kendall趋势检验等分析方法,对1970-2015年汉江流域多尺度极端降水变化特征进行分析。结果表明：（1）在旬尺度上,汉江流域EPCD较高,呈现出“西高东低”空间特征;汉江EPCP多年均值为七月下旬,空间呈现出“东部早,西部迟”的分布特征,不同流域表现出不同的年代变化规律。（2）在月尺度上,汉江流域极端降水各月分布不均,主要集中在5-9月,同年10月至次年4月为极端降水少发期。（3）在季尺度上,汉江流域极端降水夏季占比50%以上,但近期全流域夏季极端降水比例下降,其中上游主要为春季占比增加,中下游为秋季占比增加,说明夏季是影响汉江极端降水非均匀变化的关键季节。（4）在影响因素上,当东亚季风和南亚II区季风偏强时,汉江流域夏季极端降水量整体减少;当东亚季风偏弱时,夏季极端降水增幅呈南北分异,而南亚II区季风偏弱时,极端降水增幅呈东西分异。

Spatiotemporal variation of extreme precipitation regimes in the Hanjiang River Basin during 1970-2015

With the rapid development of social economy and the continuous development of ecological construction, the change of water resources in the Hanjiang River Basin plays an important role in the sustainable development of trans-regional water transfer. Thus, it is worthy to analyze the variation characteristics and influencing factors of extreme precipitation in the Hanjiang River Basin, using the peaks-over-threshold approach, extreme precipitation concentration degree (EPCD) and extreme precipitation concentration period (EPCP). The results show that (1) In terms of the "10-day" scale, the extreme EPCD in the river basin is relatively high, and it shows the distribution characteristics of "high in the west and low in the east", which illustrated that the precipitation is more uniform in the eastern part than in the western. And the EPCD in the lower reaches of Hanjiang River has a decreasing tendency in recent years, which indicated that the precipitation tends to disperse. The annual average value of EPCP in the Hanjiang River is concentrated in late July, and it shows the spatial distribution features of "early in the east, and late in the west", that is, there is earlier arrival of the flood season in the east than in the west. (2) For the monthly scale, the extreme precipitation in the study basin is concentrated in May and September, and extreme precipitation rarely occurs during the period from October of the same year to April of the following year. (3) At the seasonal scale, since the start of the 21st century, the proportion of extreme precipitation in summer in the basin has decreased, and the summer extreme precipitation has mainly changed to spring in the upper reaches, which turned into autumn in the middle and lower reaches of the basin, indicating that summer is the key season that leads to the uneven variation of the extreme precipitation. (4) As for influencing factors, the East Asian summer monsoon and South Asia II have a negative correlation with the extreme precipitation. When the East Asian summer monsoon and South Asia II are strong, the extreme precipitation in the whole river basin decreases. However, when the East Asian monsoon and South Asia II are weak, the correlations with extreme precipitation present spatial difference. The weaker the East Asian monsoon, the increase of extreme precipitation varies from north to south, while in South Asia region II, the increase of extreme precipitation varies from east to west.