Fig. 2: Stratospheric water vapor anomaly and its contributors averaged over three periods.

SWV anomaly (unit: ppmv) averaged over the first wet decade 1990–1997 (a and d); the dry decade 1998–2009 (b and e) and the second wet decade 2010–2020 (c and f) for SWOOSH (a–c) and CLaMS simulations (d–f). Regions with more than 50% missing values are blanked for SWOOSH. Following the procedure described in the method section and also in Hegglin et al.¹¹ (see their Eq. 2), ∆H₂O is decomposed into contributions from changes in H₂O entering the stratosphere (g–i), circulation changes (j–l), changes in methane entering the stratosphere (m–o) and the residuum (p–r). Black contours in a–f show anomalies relative to the climatological means (unit: %). The gray contours on g–i are the mean age of air (AoA) for each period (unit: year). The red and blue contours on j–l are positive and negative anomalies of AoA averaged over each period (unit: year). The magenta thick line indicates the climatological tropopause.