我国北方的冬季沙尘暴

本文利用我国北方100站气象记录，分析冬季沙尘暴日数的空间分布和时间演变，讨论了典型冷、暖气候时段中冬季沙尘暴日数的差异，并将1999年1月24～27日的大范围沙尘暴事件，作为我国冬季沙尘暴的典型个例，采用地面、高空天气图和卫星云阁资料作了分析。

WINTER SANDSTORM EVENTS IN EXTENSIVE NORTHERN CHINA

n the context of the meteorological record from 100 stations in the northernparts of China, covering the northwest, northeast and north of the country,investigation has been conducted for the spatial and temporal patterns of wintersandstorm days and the difference in the number between intervals of typically coldand warm climatc. A large-scale dust-raising event on January 24～27, 1999 wasdealt with in the context of surface and upper-air synoptic charts and satellite imagery.From the analyses on the number of winter sandstorm days （NWSD） of northern100 stations in 1951 ～1998, the following points are of note:（1） Winter is another season of high incidence sandstorm events, next to spring,and most of the northern stations have recorded greatly reduced NWSD during thelast more than a decade.（2） The NWSD differ in magnitude in a large scale cold and warm climatebackground. In a typically warm interval （1988 ～1997） the number is significantlyless compared to 1963 ～1972 for most of the 100 stations, a conclusion that is inagreement with that concerning the increase in dust depositing frequency in the coldPeriod over east China based on the historical documentary record since the third andespecially the 15-th century.（3） In 1988 ～1997 or 1985 ～1994 as a warm decade, the NWSD at a fewstations in Qinghai are increased a lot compared to a cold counterpart （1963～ 1972）,which is more or less related to local climate. And whether that relates tonon-meteorological factors awaits further research.From the synoptic charts and satellite imagery, it is considered that thesandstorm-dust raising event on January 24 ～27, 1999 is a large-scale happeningtypical of northern China for the past two decades, in association with class III of thecirculation pattern as a trough-ridge-trough form. The sands have the origin fromMongolia-Hetao, reaching Japan and the Ishigaki of the Ryukyu islands around 24°N.