第二届未来大气科学论坛

Using reanalysis and model data, this study investigated potential vorticity (PV) generated by diabatic cooling over the Tibetan Plateau (TP) and its associated climatic effects on adjacent regions. Results suggest that anomalous diabatic cooling over the TP exhibits a bottom-heavy vertical structure, which leads to the generated positive PV anomaly being confined within a shallow near-surface layer. The total PV generation anomaly within this shallow near-surface layer is determined by the anomalous surface PV generation flux that is thermally driven by anomalous surface cooling. Further analysis revealed a significant interannual relationship linking stronger near-surface PV generation over the TP with anomalously warm winters in eastern China. The proposed mechanism involves PV generation by surface cooling, PV transport by katabatic flows, and an attendant weakened Siberian High. The surface cooling anomaly over the TP generates a positive PV anomaly within the near-surface layer, while simultaneously induces a form of anomalous katabatic flow down the slopes of the TP. This anomalous katabatic flow transports positive PV within the near-surface layer into the region of the Siberian High, increasing the local positive PV anomaly and weakening the Siberian High. A weaker Siberian High is associated with weaker winter monsoon flow and anomalous southerlies, favoring a warm surface air temperature anomaly over eastern China. The validity of the proposed mechanism was corroborated by numerical modeling. Relative to the well-studied winter block effect of the TP, this study offers and emphasizes new aspects of the TP’s climatic effects driven by its wintertime thermal conditions.

Tibetan Plateau,Potential Vorticity,diabatic heating