近50年西藏最长连续无降水日数变化特征

Variation Characteristics of the Longest Continuous Dry Days: Tibet, 1961-2010

利用1961—2010年西藏18个站点逐日降雨资料,建立年、季最长连续无降水日数的时间序列,分析西藏最长连续无降水日数的分布特征、变化趋势及对干旱的影响,并初步分析厄尔尼诺对西藏最长连续无降水日数的可能影响。结果表明:西藏最长连续无降水日数的高值区主要位于干旱与半干旱气候区,气候越干燥的地方,越容易出现长时间的无降水天气;西藏年、季最长连续无降水日数均呈减少趋势,且年(3.1 d/10 a)和冬半年(2.8 d/10 a)减幅明显,通过了0.01以上的信度检验,并于1977年发生了由多到少的突变;长时间无降水是导致西藏干旱发生的重要原因;厄尔尼诺对西藏最长连续无降水日数具有一定的调节作用,即厄尔尼诺出现当年西藏最长连续无降水日数普遍增多,厄尔尼诺出现的次年西藏最长连续无降水日数普遍减少。

Based on daily precipitation data at 18 meteorological stations in Tibet during 1961- 2010, theauthors established annual and seasonal longest continuous dry days time series, and analyzed the distributioncharacteristics and trends of the longest continuous dry days, and the impact on drought in Tibet, and thepreliminary analysis of the possible effect of El Nino on the longest continuous dry days was conducted. Theresults showed that： the high value region of Tibet＇s longest continuous dry days was mainly located in the aridand semi arid climate region, the drier regions were more prone to prolonged weather without precipitation;annual and seasonal longest continuous dry days had a decreasing trend in Tibet, the annual and winter halfyear exhibited a significant decreasing tendency with the decrease rate of 3.1 d/10 a and 2.8 d/10 arespectively, passed 0.01 reliability test, and the descending mutation occurred in 1977; long time withoutprecipitation was an important cause of drought in Tibet; El Nino played a regulatory role in the longestcontinuous dry days, the longest continuous dry days had a general increase in El Nino years and a generaldecrease in the second year of El Nino occurrence.