Influence of the Tibetan Plateau and its northern margins on the mid-latitude Westerly Jet over Central Asia in summer

Abstract

The upper-troposphere Westerly Jet is currently maintained in the mid-latitudes of Central Asia during summer, the strength and movement of which are closely related to the variations in precipitation in arid Central Asia. However, little is known about how this Westerly Jet has changed during the Cenozoic, although it is known that the Tibetan Plateau has a crucial role in the modern Asian climate. We conducted a set of numerical experiments to examine the effects of the Tibetan Plateau and the topography of its northern margins (the Pamir Plateau, the Tian Shan mountains and the Mongolian Plateau) on the Westerly Jet in summer. The mid-latitude Westerly Jet is significantly intensified with the uplift of the Tibetan Plateau. The center of the jet stream moves about 1° to the north. This strengthening and shift in the Westerly Jet are primarily due to the strong atmospheric heat source induced by the uplift of the Tibetan Plateau. With the inclusion of the Pamir Plateau and Tian Shan mountains, the Westerly winds in the northern axis of the jet are strengthened while the southern part is weakened, resulting in a continuous northward shift in the Westerly Jet stream. Similar to the effects of the Tibetan Plateau, anomalous diabatic heating appears with the inclusion of the Pamir Plateau and Tian Shan mountains and the intensity of the Westerly Jet is slightly weakened. The Westerly Jet is also weakened, but stops moving northward, when the Mongolian Plateau is uplifted. This is a result of continuous northward warming. The mid-latitude Westerly Jet therefore experienced distinct changes during the Cenozoic in association with the development of the atmospheric heat source in summer as a result of the stepwise uplift of the Tibetan Plateau, Tian Shan mountains and Mongolian Plateau. This may have influenced the aridity of the Asian interior and the transport of eolian dust.