Link between the atmospheric thermal condition over the Tibetan–Iranian Plateaus and Eurasian–African climate through the Asian westerly jet stream

Abstract

Using monthly mean data from the European Centre for Medium-Range Weather Forecasts interim reanalysis dataset and precipitation data from the Global Precipitation Climatology Project, we investigate the connections among the atmospheric thermal condition over the Tibetan–Iranian Plateaus (TIPs), the intensity of the Asian westerly jet stream (AWJS), and climate over the Eurasian–African region during boreal summer. At the entrance of the AWJS, the tropospheric air temperature over the TIPs (TTIP) has a significant negative correlation with precipitation and a positive correlation with surface air temperature (SAT) over West Asia, Eastern Europe, and western Russia. Furthermore, the TTIP has a significant positive correlation with precipitation over Northeast Africa. In contrast, at the exit of the AWJS, the TTIP has a significant negative correlation with precipitation and a positive correlation with SAT over East Asia. The TTIP has a significant positive correlation with precipitation over Northeast Asia. This distribution of TTIP-related precipitation and SAT over the Eurasian–African region can be explained by the four-quadrant conceptual model of a straight jet streak. The enhanced temperature gradient from the mid–lower to higher latitudes over the Asian continent, associated with a high TTIP, results in the enhancement of the AWJS. Two anomalous opposite meridional circulations appear at the entrance and exit of the AWJS, respectively, and are responsible for the distribution of the TTIP-related precipitation and SAT over the Eurasian–African region.