黑河流域日降水格局及其时间变化

Daily Precipitation Pattern and Its Temporal Variability in Heihe River Basin

利用10个气象站1950-2000年日降水资料，对黑河流域的降水及其时空格局进行了研究。结果表明：①降水事件以≤5mm的降水为主，占全年降水事件的82％，0～10d间隔期占全年无降水期的40．7％，〉10d间隔期占59．3％；②年降水日数与降水量之间存在显著的正相关性（r=0．78，P〈0．01），〉10mm降水总量与年降水量呈显著正相关，而≤5mm降水总量与年降水量的相关性差；③〉10mm和≤5mm的降水总量变化范围分别为：0～262．6mm，20．3～172．7mm，变异系数分别为0．25～0．92，0．17～0．25；④近50d来，黑河流域近50d降水量的变化总体上呈平稳上升趋势，≤5mm的降水日呈现小幅下降的趋势，≥10mm的降水日呈小幅上升的趋势。0～10d的降水间隔期出现的频率总体保持不变，〉10d间隔期出现的频率出现明显的下降趋势，年内总降水日数保持不变。

Daily precipitation patterns are characterized for temporal variability, based on daily precipitation data from an area of Heihe river basin, with emphasis on 1950 to 2000 recorded by ten stations. The results show： （1）Taking the 10 stations as a whole, 82% of all of the precipitation events received at arid and semiarid sites in Heihe river basin are ≤5 mm in the past 50 years, 40.7 % of dry periods （intervals between precipitation events） are ≤10 days and 59.3 % are ≥10 days. OThere is a significantly positive correlation between rain-days and annual rainfall in Heihe river basin （r = 0.78, P〈0.01）, annual rainfall is significantly correlated with the amount of water received in events larger than 10 mm, but not with the amount of water received in events smaller than 5 mm. （3）The range of annual accumulation water received in events larger than 10 mm is 0-262.6 mm and in events smaller than 5 mm is 20.3-172.7 mm, and the Cv range is 0.25-0.92, 0.17-0.25 respectively. QIn past 50 years, it is found that the annual precipitation in most of Heihe river basin showed an increasing trend, the days with light rain （≤5 mm.d^-1 ） have been reduced slightly, the days above moderate rain （≥10 mm.d^-1） have been increased slightly, the frequency of short dry periods （≤10 days） showed no significant trend, the frequency of long dry periods （≥10 days） is found to increase remarkably, and rainy days display no evident trend.