Dynamical and Surface Impacts of the January 2021 Sudden Stratospheric Warming in Novel Aeolus Wind Observations, MLS and ERA5

Abstract

Major sudden stratospheric warmings (SSWs) are extreme dynamical events where the usual strong westerly winds of the stratospheric polar vortex temporarily weaken or reverse and polar stratospheric temperatures rise by tens of Kelvin over just a few days, and remain so for an extended period. Via dynamical modification of the atmosphere below them, SSWs are believed to be a key contributor to extreme winter weather events at the surface over the following weeks. SSW-induced changes to the wind structure of the polar vortex have previously been studied in models and reanalyses and in localised measurements such as radiosondes and radars, but have not previously been directly and systematically observed on a global scale because of the major technical challenges involved in observing winds from space. Here, we exploit novel observations from ESA’s flagship Aeolus wind-profiler mission, together with temperature and geopotential height data from NASA’s Microwave Limb Sounder and surface variables from the ERA5 reanalysis, to study the 2021 SSW