Compound Dry–Hot Conditions in South and Southeast Asia Modulated by the Arctic Stratospheric Polar Vortex

Abstract Compound dry–hot conditions increasingly threaten South and Southeast Asia, highlighting the need to understand drivers. Observations and numerical simulations reveal a robust polar–low‐latitude teleconnection: the March Arctic stratospheric polar vortex (ASPV) strongly modulates March–April compound dry–hot conditions across the region. When the March ASPV weakens, anomalous easterlies in the lower Arctic stratosphere induce corresponding tropospheric easterlies and persist through April, cooling Siberia and accelerating the mid‐latitude westerlies. The resulting anticyclonic shear drives an anomalous anticyclone over northern South and Southeast Asia. Combined with the region's climatologically dry–hot season, these processes promote compound dry–hot conditions further amplified by positive soil moisture–atmosphere feedback. Moreover, the March ASPV outweighs the preceding winter tropical sea surface temperature in shaping compound dry–hot variability in this northern sector. Our results highlight the critical role of the Arctic stratospheric anomalies in driving low‐latitude climate, helping improve risk mitigation.