巴丹吉林沙漠西南缘降水的时空变化及其与季风及沙尘暴的相关性

Precipitation’s Temporal and Spatial Variation and Its Correlation to the East Asian Summer Monsoon and the Dust Storm over the Badanjaran Desert’s Southwestern Surrounding Area

摘要: 通过分析巴丹吉林沙漠西南缘降水的时空变化特征及其与季风和沙尘暴的相关性发现：1) 该区域降水主要集中于夏季，冬季最少；各季降水频次、雨量和强度均随海拔升高而增大，夏季增幅最大。2) 各季干湿主要取决于日雨量不小于1 mm的较强降水，但在冬季，日雨量小于1 mm的弱降水也贡献良多。3) 四季较强降水(弱降水)对总降水的贡献随海拔升高而加大(减少)，说明海拔越高越易发生较强降水，但冬季除外。4) 就1971~2005年的总体变化而言，冬、春季的较强和弱降水都在显著增加，高处尤甚，秋季增加不明显，夏季则有所减少，全年与冬、春季趋势一致；总降水量的年际和年代际变化趋势取决于较强降水，但就频次而言，弱降水也不能忽视。5) 各季较强及弱降水的雨量和频次与东亚夏季风指数的年际变化间均以负相关为主，随着夏季风的总体减弱，巴丹吉林沙漠西南缘降水有所增加，冬、春季尤为显著。6) 随着冬、春季降水增多，冬、春和夏季沙尘暴明显在减少，反映出降水对沙尘暴的抑制作用；夏季降水与当季和秋季沙尘暴间显著的正相关则表明降水和沙尘暴一致减少的变化趋势掩盖了前者对后者的抑制作用。

Abstract: By analysis on the temporal and spatial variations of the precipitation amount and the rainfall frequency (number of rainfall days) over the Badanjaran Desert’s southwestern surrounding area and their relationships with the East Asian Summer Monsoon (EASM) and the dust storm, the following conclusions have been drawn: 1) The precipitation there is mostly concentrated in the summer but lest in the winter; and the seasonal precipitation amount, rainfall frequency and intensity are all increasing with the altitude, and their amplitudes reach the maximum in the summer. 2) The seasonal drought or wetness is mainly decided by the heavier rainfall, whose intensity reaches no less than 1 mm day−1, however, in winter the weaker rainfall (whose intensity is less than 1 mm day−1) can also say something important about it. 3) The seasonal heavier (weaker) rainfall contributes more (less) to the total amount or frequency with the altitude rising, except in winter, telling that the higher altitude is more ready to trigger a heavier rainfall in warm seasons. 4) In general, both the precipitation amount and the rainfall frequency due to either the heavier or weaker rainfall in winter and spring were apparently increasing during 1971-2005, resulting in that the annual total amount and frequency are also increasing, but those in summer were somewhat reducing. The general inter-annual and interdecadal tendencies of the total precipitation amount are decided by the heavier rainfall, but those of the rainfall frequency are attributed to not only the heavier rainfall but also the weaker. 5) The seasonal precipitation amount and rainfall frequency due to either the weaker or heavier rainfall especially in winter and spring were both correlated to the EASM Index (EASMI) primarily in a negative manner, i.e., with EASM weakening, the precipitation amount and rainfall frequency were both increasing over the Badanjaran Desert’s southwestern surrounding area. 6) Apparently, with the seasonal precipitation amount and rainfall frequency in winter and spring increasing, the dust storm in the same and next seasons was taking place less frequently, reflecting the precipitation’s restriction upon the dust storm. However, the positive correlations be-tween the precipitation in summer and the dust storm in the same and next seasons are telling that the precipitation’s general reduction tendency agreeing with the dust storm’s had preceded that restriction effect.