甘肃春季沙尘暴环流特征及其时间尺度诊断分析

Circulation Characters and Different Temporal Scales Diagnosis Analyses about Spring Sand-dust Storms in Gansu

根据43a甘肃春季沙尘暴日数距平序列选取了甘肃春季沙尘暴多发年和少发年。对甘肃春季沙尘暴多发年和少发年前期冬季(12月至翌年2月)和同期春季(3～5月)500hPa环流距平场合成结果表明,前期冬季东亚大槽、同期春季蒙古气旋是影响沙尘暴发生多少的主要系统。西风指数和东亚北风指数计算结果表明,沙尘暴多发年与少发年指数差异明显,沙尘暴与冬季风联系紧密。甘肃春季沙尘暴小波变换分析,清楚地反映沙尘暴不同频域的变化特征及其交替作用;不同频域小波系数变化说明21世纪初沙尘暴将趋于增加。

According to the departure sequences of spring sand-dust storm days happened in Gansu during 43 years, the years in which sand-dust storm took place at high frequency and at low frequency have been selected. The 500 hPa departure height fields during spring (Mar.-May) and pre-winter (Dec.-Feb.) synthetically showed that the pre-winter East Asian Trough and the homochronous Mongolia cyclone are the main systems influenced the spring sand-dust storms in Gansu. The calculating results of the Westerly Index and the East Asian Boreas Index indicated that there existed remarkable differentiation of indexes between in the years of sand-dust storm frequently occurred and in the years of less sand-dust storms; the East Asian circulation in pre-winter is the main background causing the spring sand-dust storms in Gansu. The Mexican Hat Wavelet transform analysis clearly reflected the different temporal scales of the spring sand-dust storms in Gansu; it also showed that there were 2 more and less phases about the spring sand-dust storms. The positive and negative extremum of different temporal coefficients wavelet transform respectively corresponded well to the phases of more spring sand-dust storm years and less spring sand-dust storms years in Gansu. The changing trend of different wavelet coefficients suggests that the spring sand-dust storms in Gansu will increase at the beginning of the 21st century.