The Asian Jet Stream Variations And Their Impacts On East Asian Climate In Boreal Summer

According to the summertime mean zonal wind and its annual variations at200hPa from1979to2010, Asian westerly jet is segmented roughly in boreal summer, using CMAP and NCEP/NCAR Reanalyses for the period of1979～2010. The meridional shifting of East Asian jet stream (EAJ), the Zonal Heterogeneity of Asian jet stream in upper troposphere and their regional climate impacts have been investigated. In addition, we study the general circulation and the atmospheric heating field of anomalies of IEjp and IAja.Finally the preceding signal of IEjp and IAja anomaly are analyzed. The major results are summarized as follow:(1) The indices-the position of East Asian summer westerly jet index index(IEjp) and Index of Asian jet stream Asymmetry(IAja)-are defined to describe the meridional shifts of EAJ and The intensity of significant differences of eastern Asian jet and western Asian jet. The IEjp and the IAja are shown that the meridional shifts of EAJ and the intensity of significant differences of eastern Asian jet and western Asian jet. High IEjp year relates to EAJ moving north from the average, vice versa. When the IAja are changed into a positive phase, it has described to the intensity of eastern Asian jet and western Asian jet have significant differences; there was no significant difference in the negative year. Moreover, the indices are not only simple in calculating, but also facilitate monitoring and application.(2) The IEjp and IAja exist interannual variations obviously. Variation of the indices exhibit notable eight years low frequency oscillation. In the1980s and1990s, there are notable interannual variability of the IEjp with periodicities of2-3a. But the IAjain the mid-1980s-4years period is significant.(3) Anomalies of IEjp and IAja have important effects on East Asian climate variations in boreal Summer and there are significant differences. Anomalies of IEjp and IAja have important effects on Summer Rainfall in China, but we find that IAja anomaly inpacts on the temperature in westhern of East Asian.(4) The meridional shifts of EAJ and the intensity of significant differences of eastern Asian and western Asian jet and the temperature anomalies in the regions from the middle-lower reaches of Yangtze River eastward to Japan are found to be related to the anomalous meridional circulation induced possibly by the anomalous diabatic heating in Tropic regions including the Western Pacific and the South China Sea.(5) The preceding the zonal wind in200hPa, Sea level pressure, The sea surface temperature and Arctic(Antarctica) Oscillation Index could be used to predict the variability of IEjp and IAje in boreal summer..