甘肃春季(3～5月)沙尘暴成因分析

Causes of Spring (Mar. to May) Sand-dust Storms in Gansu Province

甘肃春季(3～5月)沙尘暴小波变换分析清楚地反映了甘肃春季沙尘暴不同时间尺度周期振荡的交替作用。甘肃中西部自20世纪80年代以来变暖,其变暖与太阳黑子周期长度(SCL)密切相关。甘肃春季沙尘暴与甘肃中西部热力因子和降水研究表明,当冬季冷空气活动频繁,春季气温回升快,气温波动幅度大,降水偏少,甘肃春季容易发生沙尘暴。

We analyzed the periodical variation of spring (from Mar. to May) sand-dust storms in Gansu province by using the Mexican Hat Wavelet method as well as their relation with thermal factors. There is positive correlation between the departure of pre-winter (from Dec. to Feb.) ground-air temperature difference and the spring sand-dust storm days in the middle and west Gansu province; the positive and the negative departure correspond very well to the more times of spring sand-dust storm before 1980's and the less times after 1980's in Gansu respectively. Contrary, there is negative correlation between the departure of the corresponding spring ground-air temperature difference and the spring sand-dust storm days.;When the cold air that affected the region is active in winter, the temperature rises rapidly in spring, the scope of spring daily temperature range is large and the precipitation is less, the spring sand-dust storms in Gansu happened easily. Otherwise, the spring sand-dust storms in Gansu are less. Especially, the warming winter phenomena happened in the 1990's, the minimum temperature rose prominently, the scope of daily temperature range reduced; in the other words, the heavy cold airs influencing the region weakened so much, the spring dust-sand storms tended to less. Global warming is the background of the warming in the west and middle of Gansu since 1980's. Furthermore, the warming in the region related closely to the sunspot cycle length (SCL).