Synergistic contribution of soil moisture and sea surface temperature to summer Tibetan Plateau temperature

The Tibetan Plateau, particularly the eastern Tibetan Plateau (ETP), experienced extraordinarily high surface air temperature (SAT) anomalies in summer 2022. This study investigated the impact of anomalous soil moisture (SM) on the SAT over the ETP and explored the synergistic effect of SM and sea surface temperature (SST) anomalies on the ETP SAT during 1961–2022. It is found that the anomalous SM in the region from the eastern European Plain to the western Siberia Plain (EEP-WSP) remarkably affects the summer SAT over the ETP. Corresponding to lower EEP-WSP SM, the overlying upper-level higher geopotential height appears and stimulates downstream wave train from the EEP-WSP region to ETP, thereby affecting atmospheric circulation and associated SAT anomalies over the ETP. Since warmer SST anomalies in the Barents Sea and Black Sea contribute to the lower EEP-WSP SM anomalies (i.e., drier soil), the EEP-WSP SM can be considered a critical factor in bridging the Barents Sea and Black Sea SST anomalies and the ETP SAT. Moreover, the EEP-WSP SM can independently modulate the ETP SAT even when the effects of the SST anomalies are removed. The variability in the EEP-WSP SM is independent of that in the Yellow-Japan Sea (YJS) SST. Accordingly, the EEP-WSP SM and YJS SST can cooperatively and remarkably adjust the summer SAT over the ETP. The synergistic effect of EEP-WSP SM and YJS SST can regulate the ETP SAT on various (interannual, interdecadal, and trend) timescales and explain well the 2022 SAT anomaly over the ETP.