Influences of subtropical jet and Tibetan Plateau on precipitation pattern in Asia: Insights from regional climate modeling

Abstract

Large topographic features, like the Tibetan Plateau (TP) and the Rocky Mountains, have significant impacts on Earth's climate. Numerical experiments were carried out using a regional climate model in order to study the sensitivity of rainfall distribution to the TP's thermal/dynamic effects and meridional position of the subtropical westerly jet. The sensitivity experiments under the present winter conditions, characterized by weaker solar radiation and westerly jet located to the south of the TP, reveal that broad arid climate characterizes Northeast Asia, covering North China and Mongolia. The results are consistent with previous studies, indicating that TP dynamic forcing is dominant in winter. In sensitivity experiments under present summer conditions, characterized by stronger solar radiation and the westerly jet located to the north of TP, a prominent subsidence occurred over North China, where the Taklimakan and Gobi deserts are located. In summer, dynamic forcing of TP is very weak, whereas the thermal forcing of TP mainly induces subsidence. Relatively smaller mountain ranges, such as the TianShan Mountains, also modify the atmospheric circulation even during the summer season. The active convection zone along the Baiu front, which produces an elongate rain belt that extends from East China to Korea and Japan, is near the boundary of two moisture sources, transported by the westerly wind over the Eurasian continent and by the Asian summer monsoon flow. The millennial-scale variation in the location of the boundary reflects corresponding changes in East Asian climate, including monsoon intensity, storm activity, and the subtropical jet.