Quantifying the processes of accelerated wintertime Tibetan Plateau warming: outside forcing versus local feedbacks

The Tibetan Plateau (TP) has experienced an accelerated wintertime warming in recent decades under global warming, but consensus on its causes has not yet been reached. This study quantifies the processes of the warming through analyzing surface temperature budget and surface energy balance. It is found that increased diabatic heating (73%) and warm advection (27%) by an anomalous anticyclone southeast of TP are two primary processes determining the surface air warming. The former is caused by a significant increase of the TP skin temperature which warms the near surface atmosphere through increasing upward surface sensible heat flux. The land surface warming is attributed to increased absorbed radiation fluxes in which three processes are identified to be major contributors. While outside forcing which is primarily due to increased anthropogenic emissions of greenhouse gases contributes to the warming by 25% through increasing downward longwave radiation, two types of local positive feedbacks which are triggered by the land surface warming are found to contribute to most of the warming. One is the snow-albedo feedback which accounts for 47% of the surface warming by increasing surface absorption of incident solar radiation. The other is the moisture process feedback which accounts for 28% of the surface warming. The surface warming which works with increased soil water due to increased precipitation in the preceding seasons tends to promote surface evaporation and moisten the atmosphere aloft over the eastern TP, which, in turn, tends to increase downward longwave radiation and cause a further surface warming.