Tibetan Plateau Warming in May–June Intensified Pakistan Summer Flood in 2022 and 2023

The catastrophic floods that struck Pakistan in June–July of 2022 and 2023 were caused by persistent heavy convective precipitation, resulting from multiscale atmospheric interactions and dynamic forcing. This study demonstrates that the prolonged rainfall anomaly was primarily driven by low-frequency westerly waves and monsoon circulations, which were association with pronounced warming over the central-western Tibetan Plateau (TP) during the preceding May–June (MJ) period, in combination with other contributing climatic forcings. The MJ TP warming diminished the latitudinal tropospheric temperature gradients between the TP and tropical Indian Ocean, favoring a weakening and westward contraction of the North African subtropical jet stream (JS) core. This jet adjustment enhanced a low-level cyclonic circulation within the JS’s right exit region, extending from the Arabian Sea to western India–Pakistan (WIP). Simultaneously, warming over the western TP amplified the elevated heat pump effect, promoting a westward displacement of the South Asian high’s anticyclonic center during May–July. This shift likely promoted upper-level divergence over WIP while reinforcing a low-level cyclonic anomaly and westward retreat of the North African subtropical high, which, in turn, intensified and deepened westerly troughs. Furthermore, soil moisture and soil moisture–atmosphere coupling helped sustain these anomalous cyclonic circulations throughout the June–July. This positive feedback mechanism intensifies the low-level jet and moisture transport from the Arabian Sea into WIP, ultimately triggering extreme rainfall events and devastating floods.