Variations in Summer Surface Air Temperature Over the Eastern Tibetan Plateau: Connection With Barents-Kara Spring Sea Ice and Summer Arctic Oscillation

Variations in surface air temperature on the eastern Tibetan Plateau (TP-SAT) during boreal summer, related to Barents-Kara spring sea ice and summer Arctic Oscillation (AO), are investigated using observations and ERA-5 reanalysis data during 1979-2018. Results show that the primary mode of summer eastern TP-SAT (SAT_EOF1) is characterized by the consistent warming pattern with larger values over the northeastern TP, which is linked with the anticyclonic circulation located in the northeastern flank of the TP. This anticyclone enhances westward water vapor transport, warm temperature advection, and causes descending over the eastern TP, Descending further results in deceased middle level cloud cover and increased solar radiation, accordingly, favoring the eastern TP warming. Further statistical analysis reveals a robust connection between Barents-Kara spring sea ice, summer AO and SAT_EOF1. Moreover, anticyclonic anomaly located in the northeastern region of the TP acts as an important driver of this consistent warming pattern over the eastern TP, which is modulated by two individual Rossby wave trains from the northwestern Russia and northwestern Atlantic. The spring sea ice in Barents-Kara could cause decreased precipitation and reduced soil moisture in northwestern Russia during following summer, which further induces the Eurasian-like teleconnection and affects the anticyclonic anomaly situated in the northeastern flank of the TP, thereby favoring eastern TP warming. In addition, from northwestern Atlantic to northeastern region of the TP, the Rossby wave train is mainly affected by summer AO, with positive AO causing anticyclonic anomaly over northeast of the TP, thus contributing to the TP warming.