The influence of Tibetan Plateau surface warming on climate extremes across South-East Asia

With an average height greater than 4500m and an area covering approximately 2.5 million km², the Tibetan Plateau (TP) plays a crucial role in determining the large-scale atmospheric circulation across South-East Asia. Substantial intraseasonal precipitation variability is observed across TP associated with the subtropical jet location and silk road pattern. A northward shift of the subtropical jet is associated with reduced precipitation over TP. Through analysis of weather station data and satellite observations, a diurnally-varying sensitivity of the land surface to intraseasonal precipitation variability is concluded. For example, a prolonged dry spell is associated with warmer ground temperatures and increased surface sensible heat flux. Using reanalyses the influence of anomalous surface conditions across TP, associated with intraseasonal precipitation variability, on the local and remote circulation is investigated.

During a dry spell increased surface sensible heat flux deepens the planetary boundary-layer and leads to the development of a localised heat low anomaly. In the upper-troposphere surface sensible heating forms an anticyclonic anomaly above TP which induces an upper-level Rossby-wave train. The induced Rossby-wave train is associated with an anomalous cyclonic circulation across central China and a westward extension of the west Pacific subtropical high. These circulation anomalies induced by TP surface warming are associated with climate extremes across South-East Asia including an increased risk of flash drought across central China and higher probabilities of extreme precipitation across southern China. The association between land-atmosphere interactions across TP and climate extremes in South-East Asia highlight the importance of land-atmosphere feedbacks in forecasting climate extremes.