Westward extension of ENSO teleconnections links spring rainfall between northern Southeast Asia and the Arabian Peninsula

Abstract. ENSO teleconnections are not stationary, but how this nonstationarity reorganizes spring hydroclimate across Asia remains unclear. Spring rainfall is particularly important for the Arabian Peninsula, one of the world’s most arid regions, where even modest rainfall changes can affect water availability and drought risk. Here we show that a March–April rainfall seesaw between the Arabian Peninsula and northern Southeast Asia strengthened markedly after the late 1990s. During 1979–1998, ENSO-related convection and circulation anomalies remained mainly confined to the tropical Pacific–Maritime Continent sector and projected only weakly toward the Arabian Peninsula, with limited evidence of a coherent pathway linking the two regions. During 1999–2023, the ENSO-related response extended farther westward and northwestward, linking El Niño-related suppressed convection and reduced rainfall over northern Southeast Asia with enhanced rainfall over the Arabian Peninsula. This shift was associated with a reorganization of Indo-Pacific overturning, including a more distinct double-cell Walker response, a strengthened Arabian Peninsula vertical branch extending farther northward, and enhanced upper-level Rossby-type and thermal adjustment. Idealized model experiments show that western equatorial Indian Ocean heating can generate an Arabian Peninsula-sector response and that this response becomes more effective under the later-period background state. Observed changes in convection, low-level pressure and winds, and the upper-level jet and divergence further indicate that the later-period ENSO anomalies developed within a modified mean-state environment. These results identify a nonstationary ENSO teleconnection pathway in which the westward extension of tropical heating anomalies, Walker–Hadley coupling, and off-equatorial upper-level adjustment connect spring rainfall variability across Southeast and West Asia.