A New East Asian Winter Jet Stream Index And Associated Anomalies Of East Asian Winter Monsoon

According to the data analysis, we define a new winter East Asian Jet Stream(EAJS) index, which reflects very well the interannual variability of winter EastAsian Jet Stream. When index value is large (small), winter East Asian Jet Stream isstrong (weak), and its position extends east (west). The differences fields of severalmeteorological variables between high and low index years describe the climateanomalous characteristics in East Asian, which are the enhanced meridional gradientof surface temperature, the strengthened upper-level westerly jet stream movingeastward, the developed Siberian high and the significantly deepened Aleutian low atsea surface level, the deepened East Asian trough at 500hPa, the significantlystrengthened cyclonic flow associated with Aleutian low at 850hPa, the obviousnortherly anomaly over northeastern Asian, northwestern Pacific and East Asian coast,namely significantly strengthened East Asian winter monsoon. The results ofcorrelation between the index and SST, OLR indicates that strong EAJS year ischaracterized by enhanced SST meridional gradient at the position of EAJS in autumn,SSTA distribution in winter similar to that in strong East Asian winter monsoon year,but different from that in La Ni(?)a year, meanwhile, enhanced convective activity overthe tropical western Pacific and Walker circulation, and suppressed convectiveactivity over the tropical eastern Pacific. The teleconnection analysis implies that instrong EAJS years, the meridionality of general circulation over Eurasia-Pacificincreases, which favors cold air moving southwards from high-latitude, East Asianwinter monsoon becomes stronger, and vice versa. The correlation coefficients analysis between EAJS index and other indices is consistent with above results, theEAJS index can describe comprehensively the anomalous characteristics of thegeneral circulation of East Asian winter monsoon. Additionally, the PNAteleconnection pattern associated with EAJS differs significantly from that associatedwith the equatorial eastern Pacific SSTA. The EAJS index has a strong interdecadalvariability as well as a strong interannual variability. The difference of climatecharacteristics associated with EAJS index, between on the interannual time scale andon the interdecadal time scale, manifests mainly in the equatorial east central PacificSSTA.