1961-2010年新疆极端降水过程时空特征

Spatiotemporal variations of extreme precipitation events within Xinjiang during 1961-2010

采用新疆50个气象测站1961-2010年逐日降水资料,选用14个极端降水指数探讨新疆极端降水事件的发生与变化。结果表明:无论平均降水过程还是极端降水过程,均能反映新疆明显的湿润化趋势。伴随降水量的增加,降水强度及降水频率均增大,除CDD变化表现为下降趋势外,其他指数变化均呈上升趋势。分析各极端降水指数序列变化,20世纪60-70年代年际变化幅度小,稳定性好;80-90年代年际差异大,稳定性差;新疆东部各极端降水指数上升与下降趋势小幅交替出现,而北疆、南疆及全疆极端指数序列则呈明显且单一的上升趋势。各极端降水指数最大概率变异年为1986年、2009年;降水变异后,新疆弱降水过程变化不明显,但强降水过程变幅增大,易导致洪旱灾害等极端气象水文事件的发生。

With the development of global climate change, extreme climate events have drawn attention of worldwide researchers not only due to their direct impact on socio-economy, but also as climate change indicators. Human and natural systems have been affected by extreme climate events to a great extent. The main objective of our study is to detect the possible changes and intensity, tendency and frequency of extreme climate events. Xinjiang is located in the inland China, where the climate is arid to semi-arid. Xinjiang is therefore highly vulnerable to climate variability, and a better understanding of changes in extreme precipitation events plays an increasingly role in the arrangement of agricultural production and the process of agricultural planning. Fourteen extreme precipitation indices have been selected and spatiotemporal patterns of extreme precipitation events have been analyzed based on daily precipitation data from50 stations covering the period of 1961-2010 using statistical methods. The results indicate that precipitation amount is in an upward trend with increasing precipitation intensity and precipitation frequency. With the increase of precipitation, evident decrease of CDD can be found and increasing trend can be identified by RR1, RR5, RR10, R95 P, Rx1 day and Rx5 day. This result show obvious wetting tendency in Xinjiang. However, different time periods are dominated by different changing properties of precipitation regimes. With smaller variability and higher stability, precipitation amount level during 1960-1970 s is lower. The period of 1980-1990 s can be taken as the transitional period characterized by abrupt increase of precipitation amount and lower stability, and according to unsteady precipitation variations in recent years, higher precipitation variability can be found after the 1990 s. Spatially, increasing and decreasing trends of precipitation variations alternate in eastern Xinjiang with small amplitudes; however, evident increase of precipitation can be found in the northern, southern and the entire Xinjiang region.Alteration of precipitation variations was found mainly in 1986 and 2009. After occurrence of precipitation alteration, strong precipitation processes are subject to higher variability and moderate changing characteristics are found in weak precipitation processes. This study will be of great merits in terms of development of human understanding of regional responses of hydrological cycle to climate changes in Xinjiang.