Impacts of the Regional North Polar Vortex Anomalies on Summer Precipitation of the Tarim River Basin

With precipitation data of 43 stations in the Tarim River Basin and the polar vortex areas data in the Atlantic-European (polar vortex) in summer of 1961-2015, variation characteristics of the precipitation and the polar vortex, the correlation and impacts of north polar vortex anomaly on precipitation in the Basin are studied. The precipitation in the Basin has been increasing since 1961, while the polar vortex is decreasing, and a significant negative correlation is found. In negative (positive) polar vortex anomaly years, in the upper atmosphere layer, the significantly weaker (stronger) subtropical westerly jet in West Asia and Central Asia, while it is the opposite in East Asia (35°-45°N, 120°-160°E) and the Basin, where the high-middle latitude cold air and mid-low latitude warm wet air that enter the Tarim River Basin increase (decrease) and strengthen (weaken). In the middle layer, negative (positive) polar vortex anomaly may lead to stronger (weaker) Middle European ridge and the Baike Lake ridge, weaker (stronger) East Asia trough, increased (decreased) meridional circulation in the Central Asian, and converging (diverging) stream in this basin. In the low layer, negative (positive) polar vortex anomaly may lead to stronger (weaker) anomaly easterly and southwesterly (northwesterly and northeasterly), stronger (weaker) weather disturbance. More east vapor flux is found entering the Basin comparing to the west vapor flux outflowing away this Basin. Moreover, the southern and eastern vapor flux converging in the southwest borders, and the convergence of vapor flux are strengthened (weakened) in the main precipitation areas of the Basin, which all lead to the increasing (decreasing) of precipitation in the Tarim River Basin.In summer, the polar vortex anomalies in the Atlantic-European have impacts on the meridional wind, zonal wind and the vertical motion from the high latitude to the low latitude by the meridional correlations. In the meridional range of the Tarim River Basin, the meridional variation distributions of the meridional wind, zonal wind and the vertical motion are formed from high latitudes to low latitudes by the zonal correlation, which are similar to those of the Atlantic-European, and anomalies of the wind field and the water vapor transition are also triggered in the Basin and its adjacent areas, impacting the precipitation. Therefore, the north polar vortex anomalies could possibly have significant denotative meaning on the Tarim River Basin precipitation in summer.