Links between the thermal condition of the Tibetan Plateau in summer and atmospheric circulation and climate anomalies over the Eurasian continent

摘要

We examine the links between the thermal condition of the troposphere over the Tibetan Plateau with the atmospheric circulation and climate over the Eurasian continent. The temperature of the troposphere over the Tibetan Plateau is higher than the temperature in other regions at the same latitude and is consistent with the temperature of the Eurasian troposphere on an interannual timescale. The higher temperature of the troposphere over the Tibetan Plateau leads to anomalous south-north temperature gradients from mid-latitudes over the Eurasian continent to its two flanks, accompanied by anomalous easterly and westerly winds in the upper troposphere in the subtropics and at higher latitudes. Anomalous anticyclonic circulations and subsidence motions appear between the anomalous easterly and westerly winds and contribute to the high surface air temperature over West Asia, Central Asia and East Asia via anomalous vertical temperature advection in the troposphere and change in the amount of solar radiation incident on the surface. The enhanced East Asian summer monsoon associated with the high temperature of the troposphere over the Tibetan Plateau also partly contributes to the high surface air temperature over East Asia via horizontal temperature advection. The westerly wind anomalies in the north of the mid-latitudes over the Eurasian continent indicate the enhancement and northward shift of the mid-latitude westerly jet. This is related to anomalous upward motion and higher precipitation in Northeast China and North China. Sensitivity experiments based on an atmospheric model verify the impact of anomalous tropospheric heating over the Tibetan Plateau in summer on the atmospheric circulation over the Eurasian continent.