2006•Gaoyuan qixiangRequires access
The Interannual and Interdecadal Variation of Arctic Polar Vortex at 300 hPa
Hengde Zhang, Shouting Gao, Zhang You-shu
Open publisher page 3 citations
Abstract
The area size and intensity of 300 hPa Arctic polar vortex and their seasonal changes are estimated from 1949 to 2002 based upon the 54-year NCEP/NCAR reanalysis monthly meangeopotential height data.By means of linear trend estimate,Morlet wavelet analysis and binomial coefficient smooth,the interannual and interdecadal variation characteristics of300 hPa Arctic Polar vortex are studied,including the variation of area,intensity and location.The results show that:(1) Before middle age of 1970s,annual area size of Arctic polar vortex trend to rise,with small fluctuating,and after that,with clear undulating,it trend to decrease,but the size has a linear decline trend during 1949-2002.The linear variation trends of regionⅠandⅡ are much smaller than that of regionⅣ.The interannual variation in summer is the most obvious,and the variation in autumn is the smallest.The area of seasonalArctic polar vortex also trend to contract linearly,especiallyin winter.(2) Intensity ofannual polar vortex has the similar characteristics of the interannual and interdecadal variationswith area,but the linear trend is very slight.Each region resemble Northern Hemisphere about the variation of intensity,especially regionⅠ,except for local difference in some period of time.The interannual variation in summer has the largest extent,and inter-decadal variationin spring and summer is much more prominentthan in autumn.(3) The center of northern polar vortex is not at Arctic pole.The percentage of the polar vortex size in each quadrant hasdistinct difference,and it varies from January to December,which is close related to thermodynamic difference over sea-land.The main location of polar vortex hasinterannual and interdecadal variation characteristics.The percentage of the vortex size in quadrantⅠandⅡ trend to ascend,while descend in quadrantⅢ andⅣ,and the linear trend coefficient is small for quadrantⅠandⅢ.The center of polar vortex mainly displace towards Asia land and the Pacific.