Global-Scale Atmospheric Change with the Tibetan Plateau Uplift in a Coupled Climate Model (CESM)

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Large topography can affect the global climate change significantly. Many studies have revealed that the altitude of the Tibetan Plateau (TP) is related to the Asian regional climate. In order to find how the global-scale atmospheric circulation changes in response to the TP uplift in summer, a fully coupled model, Community Earth System Model (CESM), was used in this paper. Four experiments were run with the altitude of TP set to 25%, 50%, 75%, and 100% of the modern height, respectively (referred to as TP25, TP50, TP75, TP100 experiments). The results show that the uplift of the TP causes the change of the subtropical circulation over the northern hemisphere as well as the southern hemisphere. In the TP25 experiment, the South Asian High (SAH) at the 150mb is comparatively weak, and with the elevated surface heating, the vertical motion in the middle troposphere strengthens greatly. The ascending air over the TP leads to the forming and sustaining of the SAH, a dominate subsystem of the upper troposphere. The perturbation of the SAH propagates in the upper troposphere and stimulates stronger planetary waves on the globe and it also affects the circulation in the low level atmosphere. The subtropical highs over seal level strengthen over the Southern Ocean as well as the North Pacific and Atlantic Oceans. Furthermore, the westerlies around the Antarctica become stronger with the increasing altitude of the TP. This is meaningful that the stronger westerlies may be a forcing to accelerate the Cenozoic global cooling during the geological history.