Fig. 2: Evolution of anomalous atmospheric variables at 200 hPa in terms of the springtime ASO.
From: Arctic stratospheric ozone as a precursor of ENSO events since 2000s
a Regressed air temperature (shaded, °C; shading bar at bottom), ozone concentration (contour, interval: 20 ppbm), and wind anomaly (vector) at 200 hPa in February–March (t-1) against the springtime (March–April: t + 0) ASO index for the period 2002–2023. Anomalous air temperature is marked as significant at the 95% confidence level according to the Student’s t-test. For winds, areas satisfying the 95% and 85% confidence levels according to the Student’s t-test are marked in black and gray, respectively. b–e show similar figures to (a), but for March–April (t + 0), April-May (t + 1), May-June (t + 2), and June-July (t + 3), respectively. For the Student’s t-test, the degrees of freedom were fixed at 20.
