A polar mesospheric precursor of sudden stratospheric warmings observed by the Aura Microwave Limb Sounder

Abstract. The observations of the Aura Microwave Limb Sounder (Aura/MLS) indicate the existence of a polar mesospheric precursor of major sudden stratospheric warmings (SSWs). The geopotential height data of Aura/MLS from 2004 to 2021 show that a burst of a 4 day-oscillation (zonally symmetric wave with zonal wavenumber zero) occurs at the stratopause and in the mesosphere at 80° N about 17 days before the central date of the SSW. The detection of this precursor in forecast analyses of weather and climate models has the potential to extend the subseasonal forecast of SSWs from three to five weeks.