The Circulation Indices of Polar Vortex on 10hPa in Northern Hemisphere and Preliminary Analysis

A set of circulation indices are defined and calculated to characterize monthly mean polar vortex at 10 hPa geopotential heights in the Northern Hemisphere,including area-(S),intensity-(P) and centre position-(λ-c,φ-c)-indices by use of 10 hPa 1948-2007 NCEP/NCAR reanalyzed value monthly height data.These indices series are used to investigate the seasonal variation and interannual anomaly of polar vortex,together with the relation to global warming,ozone anomaly and AO.The results are as follows:(1) there is anticyclonic(cyclonic) from June to August(from September to March).The change of autumn circulation pattern is slower than spring.(2) P can be replaced by S in analysis due to the interannual synchronal variations of the intensity and area for polar vortex.The interannual(interdecadal) variation of P anomaly is significantly in January(July).(3) The anomalies of system centre position in January are more evident than in July.(4) The variations of mean temperature at mid-stratosphere in the vicinity of pole zone in January are different from in July,but they are synchronal with corresponding P and not significantly correlative with the trend of global warming.However the relationship between P and total ozone in July are obviously.(5) There is so notable correlation between P and AO that P can represent AO.