塔克拉玛干沙漠周边地区极端弱降水的时空变化特征

选用塔克拉玛干沙漠周边40个气象站1961—2009年日降水资料和4个极端弱降水指标,分析该地区极端弱降水的时空变化特征。采用M-K法和F检验对各站点降水指标的变化趋势及变化率进行检验和计算,并利用Monte Carlo模拟进行区域显著性检验。由Copula函数得到两降水指标的联合分布,计算两降水指标的联合重现期。结果表明:(1)年最长连续无降水日数(CDD)多为80~100d,呈显著减少趋势;出现频率最高的每年日降水量小于降水日序列25%分位数的日数(D25)为0~10d,呈显著增加趋势;每年日降水量小于降水日序列25%分位数的总降水量(P25)的值集中在0~1.5mm,2~3mm的P25从2000年才开始出现;出现频率最高的每年日降水量小于降水日序列25%分位数的日平均降水量(I25)为0.1~0.3mm,I25超过0.4mm的情况极少出现。(2)CDD与D25和P25各自五年一遇值的空间分布相反。除CDD和D25均大于各自五年一遇值的联合重现期较长外,其余各类型联合重现期较短。沙漠周边地区发生不同类型极端弱降水事件的概率不同。

Spatial and Temporal Characteristics of Extremely Weak Precipitation in the Area Around the Taklimakan Desert

With the daily precipitation data of 40 meteorological stations surrounding the Taklimakan Desert from 1961 to 2009 and four precipitation indices, the spatio-temporal variations of extremely weak precipitation in this area were analyzed in this paper. The Mann-Kendall method and F test were used to verify and calculate the trends and the changing rates of these indices in each station. Monte Carlo simulation was used to verify the regional significance of precipitation events and Copula function was used to determine the joint distribution and return period for every two of these indices. The results showed that: (1) CDD frequently ranged 80-100 days and exhibited a decreasing trend. The most frequent D₂₅ values ranged 0-10 days, the number of days with extremely precipitation increased over time. Most P₂₅ values ranged 0-1.5 mm, but values of 2-3 mm began to appear after 2000. I₂₅ with the highest frequency ranged 0.1-0.3 mm, I₂₅>0.4 mm was extremely rare; and (2) the spatial distribution of CDD in each 5-year period showed patterns contrasting those of D₂₅ and P₂₅. The joint return period for most values was short, and the occurrence probability of diverse types of extreme precipitation events is different.