Stratospheric impacts on Eurasian soil moisture on subseasonal timescales.

Abstract

Sudden stratospheric warming (SSW) events and soil moisture are both key sources of subseasonal-to-seasonal predictability, raising the possibility that SSWs could enhance hydroclimate predictability through soil moisture. Yet this connection remains largely unexplored. Here we show that SSWs induce a robust dipolar soil moisture response across Eurasia, with wetter conditions over the Iberian Peninsula and pronounced drying from the Iranian Plateau to northern India during the two months following SSWs. These responses occur in both surface and root-zone soil moisture and are consistently captured by reanalysis, land surface model simulations, and satellite observations. Enhanced precipitation drives the wet anomalies over Iberia, whereas anomalous near-surface warming drives drying from the Iranian Plateau to northern India. Our findings identify a previously underrecognized pathway linking stratospheric variability to subseasonal Eurasian hydroclimate predictability.