Possible Effect of the Tibetan Plateau on the "Upstream" Climate over West Asia, North Africa, South Europe, and the North Atlantic

We conduct several experiments using a fully-coupled climate model to understand the role of Tibetan Plateau (TP) surface heating in the climate variations over West Asia, South Europe, North Africa, and the North Atlantic during summer. Emphasis has been placed on the physical processes and responsible mechanisms that involve the shift of the Hadley cell and the important features of rotational and divergent response of the atmosphere to the TP heating. The relative importance of the TP to the Asian continent is also analyzed.

A heating of the TP surface leads to local increases in tropospheric temperature and the thickness of the air column due to the so-called air pumping effect. In the upper troposphere, the South Asian high intensifies and extends westward. Distinguished Rossby wave responses occur in the regions to the west of TP especially West Asia, South Europe, North Africa, and the North Atlantic. Anomalous high pressure and uniform warming appear in the entire troposphere, in agreement with the temperature-vertical heating gradient relationship proposed by previous studies, and correspondingly descending motions intensify and precipitation decreases. However, the tropical Sahel rainfall increases because of a northward shift of the intertropical convergence zone and the anomalous westerlies due to the weakening of the southeastern portion of the Atlantic subtropical high. These effects of the TP heating explain a remarkable portion of the effects by the Asian continent heating. In addition, the impacts of different magnitudes of TP surface heating are also discussed.