长江源区降水变化的时空分布规律分析

Analysis of Spatiotemporal Distribution of Precipitation Changes in the Source Region of the Yangtze River

摘要: 长江源区降水对发挥区域的水源涵养功能，维护三江源区生态具有重要的作用。利用长江源区1966~2017年的站点实测与空间再分析两套降水数据，综合线性趋势、滑动平均、Mann-Kendall检验、箱形图法和相关性检验等对源区降水的时空分布变化进行了分析。结果表明：从时间分布来看，长江源区的年际降水量表现为稳定的缓慢增加趋势，且在0.05检验水平下，2009年之后呈现出显著性增长，其增长量为多年平均增长量的2.3倍；年内降水分布不均的趋势加大，突变点2002年之后，出现极端降水月的概率增加了近3倍，6~9月降水量在全年中的占比增加了11%。从空间分布上看，源头区降水偏小，变化趋势与面平均降水基本一致；下游出口处降水丰富，发生极端降水月的频率也更高，各站点表现出不稳定的变化趋势。气候变化背景下，长江源区的降水在时空分布上都存在较大的异质性，降水量的增加主要集中在了下游出口区域的汛期，这可能使源区的水生态面临更加不利的环境。

Abstract: Precipitation plays an important role in exerting the water conservation function and maintaining the ecology in the source region of the Yangtze River. Based on the two different kinds of dataset including gauged point data and reanalysis distribute data in 1966~2017, the spatiotemporal distribution of the precipitation changes was analyzed by the linear regression, moving average, Mann-Kendall test, box plot method, and correlation test, etc. The results show that the annual precipitation in the source area presented a steady and slow increasing tendency in terms of time distribution; furthermore, at the 0.05 test level, the tendency became significant in 2009 which was 2.3 times the average annual increase. The trend of uneven distribution of precipitation during the year had increased that after the mutation point in 2002, the probabilities of the month with extreme precipitation increased to triple, and the proportion from June to September was increased by 11%. In terms of spatial distribution, the precipitation in the source area was small, and the changing trend was basically consistent with the average surface pre-cipitation; while the precipitation of downstream outlet was abundant, meanwhile, the same features were expressed in the frequency of extreme precipitation months, and each site shows an unstable trend of change. Under the global climate change, the precipitation in the source region of the Yangtze river has great heterogeneity in the spatial and temporal distribution, and the increase of precipitation was mainly concentrated in the flood season of the downstream export area, which may make the water ecology in the source area face more adverse environment.