4/10 How often do SSW events occur? Roughly every 2 years, but with high decadal variability. Especially the 1990s showed very few SSWs, the longest absence since at least 1850 (see https://t.co/nbNYnTBzIX). pic.twitter.com/VuoeawL1AK

— Daniela Domeisen (@Domeisen_D) November 19, 2021