Remote modulation of European blocking on 2022 Pakistan summer extreme rainfall: the bridge role of Tibetan Plateau

In the summer of 2022, extreme rainfall struck Southern Pakistan, causing catastrophic floods and severe damage to both ecosystems and human communities. Previous studies have linked this extreme rainfall to the European blocking high, yet the underlying physical pathways remain elusive. Using observational data and numerical simulation, this study demonstrates a critical bridge role of the Tibetan Plateau (TP) in conveying the remote effects of European blocking on Pakistan rainfall. On the one hand, the extreme rainfall deficiency around the southeastern TP and its attendant anomalous diabatic cooling directly drive pronounced lower-level easterly anomalies over the northwestern Indian subcontinent, thereby channeling moisture westward and boosting rainfall within Southern Pakistan. This mechanism surpasses the influence of moderate tropical SST anomalies observed in this year. On the other hand, the southeastern TP rainfall itself is regulated by the record-breaking European blocking. The enhanced European blocking stimulates an atmospheric Rossby wave train propagating to the east of the TP and reinforces the anomalous upper-tropospheric anticyclone there. This anticyclone, combined with unique thermal structure over the TP, induces intense descent and reduced rainfall around the southeastern TP. Both statistical analysis during 1979–2022 and model simulation results jointly corroborate these physical processes observed in 2022. Hence, this study clearly establishes the physical linkage among European blocking, TP heating, and Pakistan extreme rainfall.