Sudden Stratospheric Warmings

Abstract

Sudden stratospheric warmings (SSWs) are impressive fluid dynamical events in which large and rapid temperature increases in the winter polar stratosphere (∼10-50 km) are associated with a complete reversal of the climatological wintertime westerly winds. SSWs are caused by the breaking of planetary-scale waves that propagate upwards from the troposphere. During an SSW, the polar vortex breaks down, accompanied by rapid descent and warming of air in polar latitudes, mirrored by ascent and cooling above the warming. The rapid warming and descent of the polar air column affect tropospheric weather, shifting jet streams, storm tracks, and the Northern Annular Mode, making cold air outbreaks over North America and Eurasia more likely. SSWs affect the atmosphere above the stratosphere, producing widespread effects on atmospheric chemistry, temperatures, winds, neutral (nonionized) particles and electron densities, and electric fields. These effects span both hemispheres. Given their crucial role in the whole atmosphere, SSWs are also seen as a key process to analyze in climate change studies and subseasonal to seasonal prediction. This work reviews the current knowledge on the most important aspects of SSWs, from the historical background to dynamical processes, modeling, chemistry, and impact on other atmospheric layers.

Seasonal prediction of the boreal winter stratosphere

“…After the seminal works by Dunkerton (1999, 2001), much attention has been brought to the link between the stratosphere and troposphere, in terms of dynamics and predictability. Various time scales have been explored, from subseasonal to centennial (Kidston et al 2015), with emphasis given to sudden stratospheric warming events-SSWs (Matsuno 1971;Baldwin et al 2021). These are abrupt disruptions of the SPV that can affect the tropospheric circulation for up to two months (e.g.…”

A Study of False Alarms of a Major Sudden Stratospheric Warming by Real-Time Subseasonal-to-Seasonal Forecasts for the 2017/2018 Northern Winter

“…Second, it is obvious that one can extend the present approach to other years and systems. Some years are likely to prefer more forecasted MSSWs than others, as various interannually varying external factors, such as the Quasi-Biennial Oscillation and El Niño/Southern Oscillation, are known to affect the occurrence of MSSWs [5]. It is also possible that some systems exhibit different false alarm MSSWs than others.…”

“…A strong downward influence can occur when the stratosphere experiences significant anomalies, such as sudden stratospheric warmings (SSWs) [3]. SSWs are a dramatic phenomenon, during which the polar vortex largely distorts or even breaks down, accompanied by a strong warming in the polar stratosphere [4,5]. An SSW is often classified as a major SSW (MSSW) if the zonal mean zonal wind at 60 • N, 10 hPa reverses from westerly to easterly [6,7].…”

The Evaluation of the North Atlantic Climate System in UKESM1 Historical Simulations for CMIP6

“…Large uncertainty remains in the simulation of the AMOC (Reintges et al., 2017) and AMV (Martin et al., 2014; Menary et al., 2018). Furthermore, recent decades have seen large swings in the number of sudden stratospheric warmings events (Cohen et al., 2009; Gillett et al., 2002), which are known to have impacts on North Atlantic seasonal weather (Baldwin et al., 2020). The distinction between stratospheric forcing and response with other modes of tropospheric and ocean variability is currently an outstanding question (Omrani et al., 2014).…”