Large-scale dynamic processes during the minor and major sudden stratospheric warming events in January–February 2023

Abstract

Using data from reanalyses of meteorological information, this study examines peculiarities of the thermodynamic regime of the Arctic stratosphere in the winter season of 2022–2023. For this purpose, components of the global meridional circulation, wave activity fluxes, volume of polar stratospheric clouds type I (PSC NAT) are analyzed, as well as changes in these indicators during sudden stratospheric warming (SSW) events formed in January–February. The main features of the 2022–2023 winter season were the following: (1) a persistent cold stratospheric polar vortex was observed until mid-January, which caused the PSC NAT volume growth to its maximum values since 1980; (2) enhanced wave activity from mid-January led to the formation of a minor SSW at the end of January, an increase in the temperature of the lower stratosphere and a sharp reduction in PSC NAT; (3) a week of intensification of the polar vortex was then observed, followed by a weakening due to the next burst of wave activity propagation during the second SSW event in mid-February. This second SSW event was major, accompanied by a reversal of the mean zonal wind, which lasted until early March; (4) meridional heat flux in January–February 2023 was the highest since 1948, resulting in unprecedented warming of the lower Arctic stratosphere and preventing ozone depletion in March; (5) the minor SSW at the end of January was accompanied by a more intense change in the meridional circulation than the major SSW in mid-February. Formation of ozone mini-hole over Northern and Central Europe in February 2023 was associated with the strengthening of the anticyclone, leading to a stratopause elevation and northward transport of ozone-poor air masses from the subtropics along the western periphery of the anticyclone additionally to related to the major SSW temperature changes affected the ozone concentration in the lower stratosphere.