Based on the NCEP/NCAR reanalysis data, China station precipitation data from 1960 to 2008, and aerosol optical depth （AOD） data in northern China from 1980 to 2004, this paper investigates the variability of winter...Based on the NCEP/NCAR reanalysis data, China station precipitation data from 1960 to 2008, and aerosol optical depth （AOD） data in northern China from 1980 to 2004, this paper investigates the variability of winter snow/rainfall in northern China and the associated atmospheric circulation and aerosol distribution characteristics by using composite analysis. The results show that winter precipitation in northern China has been generally increasing since the 1960s. Among the winters of 1990 2008, the years with more rain/snow （MRSYs） are 1998, 2003, and 2006, while the years with less rain/snow （LRSYs） are 2005, 1997, and 2001. Composite analysis finds that MRSYs and LRSYs are as follows the main differences of atmospheric 1） In MRSYs, strong low-level cold circulation in East Asia between air over the northern polar region and Taymyr Peninsula migrates southward to northern China （Northwest, North, and Northeast China）, establishing a channel favoring continuous southward tronsport of cold air. In LRSYs, however, this cold air channel does not exist. 2） In MRSYs, the frontal zone and westerlies are over North China, and the low-level geopotential height field from eastern China to West Pacific exhibits an ＂east high, west low＂ pattern, which is conducive to easterly and southerly airflows moving northward along 110°E. In LRSYs, the 500-hPa prevailing westerly winds stay far away from China and the low-level southeasterlies move to higher latitudes, which are disadvantageous to the development of precipitation in northern China. 3） In MRSYs, large-scale upward motions combined with local-scale updrafts develop into strong slanted climbing airflows, forming a vertical circulation that favors the generation of heavy snows in eastern China. In LRSYs, the vertical circulation moves eastward into the Pacific Ocean. Furthermore, the correlation analysis on AOD and winter precipitation during the period 1980 2004 in northern China reveals that AOD differs significantly between MRSYs and LRSYs and the annual variation of winter rain/snow is positively correlated to the annual variation of AOD with a correlation coefficient of 0.415 at the 0.001 significance level.展开更多
基金Supported by the National Key Basic Research and Development(973)Program of China(2011CB403404and2011CB403401)Basic R&D Fund of the Chinese Academy of Meteorological Sciences(2009Y002)International Sci.&Tech.Cooperation Program of the China Meteorological Administration(2009DFA21430)
文摘Based on the NCEP/NCAR reanalysis data, China station precipitation data from 1960 to 2008, and aerosol optical depth （AOD） data in northern China from 1980 to 2004, this paper investigates the variability of winter snow/rainfall in northern China and the associated atmospheric circulation and aerosol distribution characteristics by using composite analysis. The results show that winter precipitation in northern China has been generally increasing since the 1960s. Among the winters of 1990 2008, the years with more rain/snow （MRSYs） are 1998, 2003, and 2006, while the years with less rain/snow （LRSYs） are 2005, 1997, and 2001. Composite analysis finds that MRSYs and LRSYs are as follows the main differences of atmospheric 1） In MRSYs, strong low-level cold circulation in East Asia between air over the northern polar region and Taymyr Peninsula migrates southward to northern China （Northwest, North, and Northeast China）, establishing a channel favoring continuous southward tronsport of cold air. In LRSYs, however, this cold air channel does not exist. 2） In MRSYs, the frontal zone and westerlies are over North China, and the low-level geopotential height field from eastern China to West Pacific exhibits an ＂east high, west low＂ pattern, which is conducive to easterly and southerly airflows moving northward along 110°E. In LRSYs, the 500-hPa prevailing westerly winds stay far away from China and the low-level southeasterlies move to higher latitudes, which are disadvantageous to the development of precipitation in northern China. 3） In MRSYs, large-scale upward motions combined with local-scale updrafts develop into strong slanted climbing airflows, forming a vertical circulation that favors the generation of heavy snows in eastern China. In LRSYs, the vertical circulation moves eastward into the Pacific Ocean. Furthermore, the correlation analysis on AOD and winter precipitation during the period 1980 2004 in northern China reveals that AOD differs significantly between MRSYs and LRSYs and the annual variation of winter rain/snow is positively correlated to the annual variation of AOD with a correlation coefficient of 0.415 at the 0.001 significance level.
