Dynamic effects of the Tibetan Plateau on the sustained drought in southwest China

A continuous drought event happened in Southwest China from the winter of 2009 to the spring of 2014, which has a wide range of impacts and a long duration, causing great economic losses to southwest China.  This research focuses on the dynamic field anomalies of the Tibetan Plateau during this event using statistical analysis methods. Moreover, a further conclusion is drawn about the mechanism of the dynamic effect of the Tibetan Plateau on drought in Southwest China. And a regression model is given. Here we show that, the absolute values of relative divergence, relative vorticity and vertical velocity of the lower layer over the Tibetan Plateau were abnormally low during the winter half year from 2009 to 2014, that is, the downdraft and anticyclone over the Tibetan Plateau were weaker than usual. It would weaken the southward cold airflow from the north of the Tibetan Plateau, while the westerly wind from dry central Asia would intensify on the south of the plateau. As a result, the intersection position of the cold and warm air shifted to north and to east, so that a larger area of the southwest China was controlled by the warm and dry air mass, which was against the precipitation. The conclusion and regression model will be referential to the forecast of drought in Southwest China and help reduce damages.