The impact of tropospheric blockings on duration of the sudden stratospheric warmings in boreal winter 2023/24

Abstract. The winter 2023/24 exhibited remarkable stratospheric dynamics with multiple sudden stratospheric warmings (SSWs). Based on the fifth generation European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis (ERA5) polar-cap averaged 10 hPa zonal wind, three major SSWs are identified – an extremely rare occurrence in a single winter. Two of three SSWs were short-lived, lasting under 7 days. In this study, we give an overview of the three SSWs that occurred in winter 2023/24 and focus on the impact of tropospheric forcing on their duration. Blocking high-pressure systems are shown to modulate wave activity flux into the stratosphere through interactions with tropospheric planetary waves, depending on their location. The rapid termination of the first SSW (14–19 January 2024) is linked to a developing high-pressure system over the North Pacific. The second SSW (16–22 February 2024) terminated quickly due to more contributing factors, one of which was a high-pressure system developed over the Far East. The third SSW (3–28 March 2024) was a long-duration canonical event extending to levels below 100 hPa. In contrast to two short-lived SSWs in winter 2023/24, the tropospheric forcing was sustained around the SSW onset in March 2024, allowing a long event to develop. We also note that conditions for these SSWs were particularly favorable due to external factors, including an Easterly Quasi-Biennial Oscillation (QBO), the presence of El Niño conditions of the ENSO cycle, and the proximity to the solar maximum.