雅鲁藏布江流域降水时空变化特征

雅鲁藏布江流域是全球气候变化的敏感区,该流域降水变化对青藏高原的水系统、生态系统和山地灾害系统的演变具有重要影响。本文通过流域水文分析,将雅鲁藏布江流域的三大水资源区细分为9个分区。基于雅鲁藏布江流域1979—2018年降水数据,综合分析了雅鲁藏布江流域及9个分区的年、干湿季、月降水量以及日、小时尺度极端降水的时空变化特征,探讨了降水和典型大尺度大气环流因子的相关性。结果表明：① 1979—2018年间,在流域尺度上,各时间尺度降水整体上均呈上升趋势。其中,年降水量上升趋势最大,为2.5 mm·a^-1;年、干湿季降水量以及典型小时尺度极端降水（Rx3hour、Rx12hour）均在95%信度水平下显著上升。在水资源分区尺度上,各分区不同时间尺度降水的变化趋势呈现更明显的非一致性,所有分区除小时尺度极端降水均呈上升趋势外,其余时间尺度降水的趋势变化方向各异。② 雅鲁藏布江流域降水存在明显的空间分异性,且降水空间分异性会随着降水指标时间尺度的缩短而增强。各时间尺度降水整体上均呈现出自东部向西部逐渐减少的趋势,流域东南部（分区Ⅲ-2）始终是高值中心,流域中西部（分区Ⅰ-2、Ⅱ-1）存在区域性高值中心。③ 北半球副热带高压和北半球极涡对雅鲁藏布江流域降水变化具有显著影响。研究结果有助于掌握当地降水的多尺度变化特征,可为雅鲁藏布江流域和青藏高原地区的水循环研究、水资源开发利用和山洪灾害防治等提供科学基础。

Spatio-temporal variation of precipitation in the Yarlung Zangbo river basin

The Yarlung Zangbo river basin (YZRB) is sensitive to global climate change. The precipitation changes in the YZRB have a great impact on the evolutions of water system, ecosystem and mountain disaster system on the Qinghai-Tibet Plateau. In this study, we divided three water resources regions of the YZRB into nine subregions through hydrological analysis. Based on precipitation data within the YZRB from 1979 to 2018, we examined the spatio-temporal variations of precipitation at annual, wet and dry seasons, monthly scales, daily and hourly extreme precipitation in the study area and its nine subregions. We further discussed the correlation between precipitation and typical large-scale atmospheric circulation factors. The results showed that: (1) From 1979 to 2018, at the whole basin scale, precipitation at each time scale showed an overall upward trend. Among them, annual precipitation showed the largest increasing trend of 2.5 mm·a^-1. Annual precipitation, dry and wet precipitation, and typical hourly scale extreme precipitation (Rx3hour and Rx12hour) increased significantly at the 95% confidence level. At the regional scale, the variation trend of precipitation at different time scales in each subregion showed more obvious inconsistencies. Except for the increasing trend of hourly scale extreme precipitation, the trends of precipitation in all the subregions were different. (2) There was an obvious spatial heterogeneity of precipitation in the YZRB, and the spatial heterogeneity of precipitation did increase with the shortening of the precipitation time scale. The precipitation at each time scale showed a gradual decreasing trend from the east to the west. The southeastern part of the YZRB (i.e. subregion Ⅲ-2) had been the center of high value, and the central and western parts (i.e. subregions Ⅰ-2 and Ⅱ-1) had a regional high value center. (3) The Northern Hemisphere Subtropical High (NHSH) and the Northern Hemisphere Polar Vortex (NHPV) had significant effects on precipitation changes. The results can help us to understand the characteristics of local precipitation at multiple scales, and provide a scientific basis for water cycle research, water resources development and utilization, and prevention of flash flood disasters in the YZRB and the Qinghai-Tibet Plateau.