第一届未来大气科学论坛

The Freeze-Thaw process on the Tibetan Plateau (TP) plays a crucial role in local phenology and atmospheric circulation. Utilizing observational and reanalysis data from 1979 to 2018, this study found that the winter TP Freeze-Thaw state (TPFT) explains nearly 20% of the variability in the East Asian summer monsoon (EASM) during Meiyu season (June–July). Results indicate that as the TP trends towards a frozen state, the winter TP soil moisture (TPSM), closely linked to the freeze-thaw process, shows negative anomalies. The negative anomalies can persist into the Meiyu season, causing reduced surface downward longwave radiation and decreased low cloud cover, which in turn result in negative surface air temperature (SAT) anomalies. The negative SAT anomalies act as a link between the TPFT and the EASM, inducing an anomalous anticyclone over the northwest Pacific during the Meiyu season and leading to positive precipitation anomalies in the Yangtze River Basin. Furthermore, the numerical experiments demonstrate that TPFT anomalies play a pivotal role. Finally, hindcast experiment outputs reveal that incorporating winter TPFT as a predictor significantly improves the crossvalidated prediction skill, with the model explaining over 54% of the variance in the EASM.

East Asian summer monsson,Meiyu,Interannual variability,Tibetan Plateau,Freeze-thaw