近40a青海湖流域逐日降水和气温变化特征

Daily Precipitation and Temperature Variations in Qinghai Lake Watershed in Recent 40 Years

利用青海湖流域内刚察气象站1958-2001年的逐日降水和气温资料,分析了流域内的气候变化特征。结果表明,日降水量P≤5 mm的降水总量以9 mm/10 a的速率显著减少,已从1960 s的130.8 mm/a减少为1990 s的116.2 mm/a,而P≥20 mm的降水总量以9 mm/10 a的速率显著增加,已从29.7 mm/a增加为36.9 mm/a;连续无降水最长天数由1960 s的32 d/a增加为1990 s的45 d/a,至少10 d连续无降水总天数由103 d/a增加为145 d/a。逐年平均温度40 a来明显升高,已从1960 s的-0.7℃升至1990 s的0.1℃,且与逐年极端低温升高有较好相关性。1990 s与1960 s的同日平均气温相比,已有261 d变暖(占年天数的71.2%),且主要发生在冬季。这种气候变化特征对流域内的青海湖水位和河川径流有重要影响。

The daily precipitation （P） and temperature changes in the Qinghai Lake watershed from 1958 to 2001 were analyzed using the records from Gangeha Meteorological Station. Results show that the yearly total rainfall of 0 〈 P 〈 5 mm decreased significantly from 130. 8 mm/a in 1960s to 116.2 mm/a in 1990s at a rate of -9 mm/10 a, whereas the yearly total rainfall of P≥20 mm increased from 29.7 mm/a in 1960s to 36.9 mm/a in 1990s at a rate of 9 mm/10 a. The longest dry period expanded from 32 d/a in 1960s to 45 d/ a in 1990s, and the total days for more than 10 successive no - rainfall days changed from 103 d/a to 145 d/a. The average annual temperature increased from -0.7 ℃ in 1960s to 0.1 ℃in 1990s, and closely connected with the extreme low temperature changes. The daily temperature in 1990s was much higher than that in 1960s, and its increase mainly occurred in winter. These climatic changes had great impacts on Qinghai Lake level and runoffs in this watershed.