第八届青年地学论坛

The precipitation over Mediterranean Basin, one of the cradles of world civilization, has been declared as a climate change hotspot. Here the impact of the arctic stratospheric polar vortex on the mediterranean precipitation in wet (winter) season is reavealed based on reanalysis data and further reverified by large scale ensemble experiences forvced with a weak (WPV) or strong (SPV)  stratospheric polar vortex. It is found that mediterranean precipitation is anomalously strong under WPV condition through mutiple mechinisms, and vice visa under SPV condition. On monthly timescale, under WPV condition, the qusia-stationary wave train originated from Atlantic region propagating to Europe continent is stronger, resulting in anomolous northerly around 30°E over Mediterranean Basin. The anomolous northerly is companied by warming advection, which further contribute to upward motion and and enhanced precipitation. On synoptical timescale, under weak stratospheric polar vortex condition the negative meridional temperature gradient in lower troposphere around Mediterranean Basin is enhanced, resulting in enhanced forontogensis progress and cyclonical activity, which is usually companied by enhanced precipitation. Furthermore, the southward shift of westerly jet over atlantic ocean under WPV condition lead to enhanced transpotation of water vapor over the west part of Mediterranean Basin, feeding Mediterranean precipitation. Our results suggest that stratospheric variability should be considered when studying the long-term trend of mediterranean precipitation under global warming.

平流层极涡