中蒙强、弱沙尘暴年春季平均环流及沙尘活动变化分析

利用NCEP/NCAR再分析资料,对比分析了中蒙东、中及西区强、弱沙尘暴年春季(3—5月)平均环流的特征和差异,讨论了过去50年3分区沙尘暴活动的变化。主要结论是:(1)根据诱发沙尘暴的诱生系统、沙尘源地、冷空气入侵路径及主要影响,中蒙沙尘暴活动区可以划分为中蒙东区、中区及西区3个区系,并分区整体讨论与预测中蒙3分区的沙尘活动。(2)中蒙东区沙尘暴强年春季盛行日本海或中国东北低压活动,常随偏东的北路及东北路冷空气入侵,带来蒙古国东部的沙尘,造成蒙古东部及中国华北的沙尘天气;而弱年春季日本海及东北低压活动则少。(3)中蒙中区沙尘暴强年春季盛行蒙古低压,多西北路及偏西的北路冷空气入侵,常造成中蒙南边界西段附近的沙尘暴天气;而沙尘暴弱年春季则相反。(4)中蒙西区沙尘暴强年春季盛行南疆热低压,多西路冷空气入侵,诱发沙尘暴,常影响南疆及柴达木盆地等;弱年春季则相反。(5)近50年中蒙地区的沙尘暴活动呈波动变化,荒漠化环境、特别是大气环流的变化是导致上述3个分区沙尘活动波动变化的主要原因。主要从大气环流角度考虑,在目前全球增暖持续的背景下,近1—2年应注意中、东区(特别是东区)沙尘活动加强的可能性。

ANALYSES OF SPRING MEAN CIRCULATIONS FOR STRONG AND WEAK DUST-STORM ACTIVITY YEARS IN CHINA-MONGOLIA AREA

The China-Mongolia(CM) area is one of major duststorm(hereafter DS) regions in the world.In view of the different features of DS activities in various subregimes of the CM area,firstly,the CM DS area covering North China and Mongolia is divided into three sub-regimes: the east-,middle-and west-CM subareas;secondly,the mid-and lower-level mean circulation features and differences for springs with strong and weak DS activities in the three sub-regimes are further analyzed,utilizing the NCEP/NCAR reanalyzed gridded data and observed DS frequency data in the CM area,and the composite analysis method.The main conclusions are as follows:(1) Due to differences in the DS-inducing systems,dust origins,routes of cold air,and main DS-hit areas,the whole CM DS area is divided into three subregimes: the east-,middle-and west-CM sub-areas.(2) In the strong DS springs of the east sub-regime,the middle-and lower-level troughs or cyclones frequently dominated over the Sea of Japan and Northeast China.The cold air intrusion along a north by east-or northeast-route brought about the DS activity in East Mongolia,Beijing,and Northeast China,and dusty weather in Korea,Japan and Taiwan.But nearly vice versa in weak DS springs.(3) In the strong DS springs of the middle sub-regime,the Mongolia troughs or cyclones were major DS-inducing systems.The strong cold air intrusion along a northwest-or north by west-route caused the DS in the West and Central Inner-Mongolia,the Gansu Corridor and West-and South-Mongolia.In weak DS springs,the opposite is nearly true.(4) In strong DS springs of the west sub-regime,heat lows prevailed over the South Xinjiang,and the west wind in the south edge of the South Xinjiang Basin was so strong that the cold air intrusion along a west route induced the DS in South Xinjiang,the West Gansu Corridor and the Caidam Basin;and vice versa in weak DS springs.(5) In the past 50 years,the middle-subregimes DS activities played the most important role in CM DS activities,but in recent years it is necessary to pay more attention to the east-subregimes DS activities under backgrounds of the global warming and strengthening Mongolia ridges in spring.