黄河上游降水变化分析

黄河上游是黄河流域重要的水源涵养区，径流占流域多年平均(1956—2000年)总径流的62%，降水变化不仅是水源的主要影响因素，也关系到涵养能力的变化。本文利用黄河上游43个气象站1960—2021年逐日降水系列数据，基于小波分析划分周期，采用Mann-Kendall检验法、距平法、频率曲线法等对上游区降水变化进行分析，结果表明：(1)黄河上游降水可划分出1963—1981年、1981—1999年、1999—2018年三个明显的周期;(2)1960—2021年年降水量以4.9 mm/10a的趋势增加，三个周期时段内年降水量的倾向率分别为-0.9 mm/10a，-1.0 mm/10a，46mm/10a;(3)1960—2021年年降水量距平百分率在-15%～15%的正常年份占比74%，距平百分率在-30%～-15%的轻旱年份和15%～30%的轻涝年份分别占比15%和8%;距平百分率在30%～40%的中涝年份占3%，旱涝年份基本发生在1963—1981年、1999—2018年两个周期;(4)三个周期时段日降水量具有差异的主要是频率小于10%的降水，且随海拔变化有差异，表现为1999—2018年玛沁站25～45.4 mm/d降水量比以往增强，1999—2018年临夏站20～50 mm/d降水量比以往增强，1963—1981年乌审召站50～65 mm/d降水量比以往增强。

Analysis of precipitation changes in the upper basin of the Yellow River

The upper basin of the Yellow River is an important water source conservation area in the Yellow River Basin，with natural runoff accounting for 62% of the annual average(1956-2000) total runoff.Precipitation changes are not only the main influencing factor on water sources，but also related to changes in conservation capacity.Based on wavelet analysis，this paper uses a series of daily precipitation data from 43 meteorological stations in the upper basin of the Yellow River from 1960 to 2021 to analyze the precipitation changes in the upper basin，using Mann Kendall test，anomaly method，frequency curve method，etc.The results show that：(1) the precipitation in the upper basin of the Yellow River can be divided into three distinct periods：1963 to 1981，1981 to 1999，and 1999 to 2018;(2) The annual precipitation from 1960 to 2021 shows an increasing trend of 4.9 mm/10 a，and the trend rates of annual precipitation during the three periods are -0.9 mm/10 a，-1.0 mm/10 a，and 46 mm/10 a，respectively;(3) From 1960 to 2021，74% of normal years have an annual precipitation anomaly percentage of -15% to 15%，while light drought years with an anomaly percentage of -30% to -15% and light flood years with an anomaly percentage of 15% to 30% account for 15% and 8%，respectively;3% of flood prone years have a percentage of anomaly between 30% and 40%.Drought and flood years generally occur in two periods：1963-1981 and 1999-2018;(4) The main difference in daily precipitation during the three periods is the frequency of precipitation less than 10%，which varies with altitude.The precipitation at Maqin Station from 1999 to 2018 increases at a rate of 25-45.4 mm/d compared to the past.The precipitation at Linxia Station from 1999 to 2018 increases at a rate of 20-50 mm/d.From 1963 to 1981，the precipitation at Wushenzhao Station increases at a rate of 50-65 mm/d compared to the past.