Observed Relationships Between Sudden Stratospheric Warmings and European Climate Extremes

Abstract

Sudden stratospheric warmings (SSWs) have been linked with anomalously cold temperatures at the surface in the middle to high latitudes of the Northern Hemisphere as climatological westerly winds in the stratosphere tend to weaken and turn easterly. However, previous studies have largely relied on reanalyses and model simulations to infer the role of SSWs on surface climate and SSW relationships with extremes have not been fully analyzed. Here, we use observed daily gridded temperature and precipitation data over Europe to comprehensively examine the response of climate extremes to the occurrence of SSWs. We show that for much of Scandinavia, winters with SSWs are on average at least 1 °C cooler, but the coldest day and night of winter is on average at least 2 °C colder than in non‐SSW winters. Anomalously high pressure over Scandinavia reduces precipitation on the northern Atlantic coast but increases overall rainfall and the number of wet days in southern Europe. In the 60 days after SSWs, cold extremes are more intense over Scandinavia with anomalously high pressure and drier conditions prevailing. Over southern Europe there is a tendency toward lower pressure, increased precipitation and more wet days. The surface response in cold temperature extremes over northwest Europe to the 2018 SSW was stronger than observed for any SSW during 1979–2016. Our analysis shows that SSWs have an effect not only on mean climate but also extremes over much of Europe. Only with carefully designed analyses are the relationships between SSWs and climate means and extremes detectable above synoptic‐scale variability.

The Remarkably Strong Arctic Stratospheric Polar Vortex of Winter 2020: Links to Record‐Breaking Arctic Oscillation and Ozone Loss

“…These relationships are commonly expressed using metrics that describe phases of the “Northern Annular Mode” (NAM), a pattern that characterizes meridional shifts of mass into or out of the polar cap throughout the atmospheric column (note that the NAM and AO are often used interchangeably; Baldwin, 2001; Thompson & Wallace, 2000). Anomalously strong or weak polar vortex states correspond to positive or negative phases of the stratospheric NAM, respectively, and these tend to be followed in the troposphere by positive or negative AO events, which may last for weeks to months and alter patterns of surface temperatures and precipitation (Baldwin & Dunkerton, 2001; Domeisen, 2019; Dunn‐Sigouin & Shaw, 2015; Kidston et al, 2015; King et al, 2019; Limpasuvan et al, 2005; Orsolini et al, 2018; Polvani & Kushner, 2002; Tripathi et al, 2015). Downward wave coupling events can not only strengthen the polar vortex but also directly induce tropospheric circulation patterns consistent with a positive AO on short time scales (Dunn‐Sigouin & Shaw, 2015; Shaw & Perlwitz, 2013).…”

Comparison of stratospheric evolution during the major sudden stratospheric warming events in 2018 and 2019

“…Recently, in 2018 and 2019, two major SSWs occurred continuously during the Arctic winters (e.g., Rao J et al, 2018, 2019b, 2020). The 2018 SSW, with a central date of 12 February 2018, was found to be related to the extremely cold winter over the European region (King et al, 2019; Lü ZZ et al, 2020) and ionospheric perturbations over the China sector (Liu GQ et al, 2019). The 2018 SSW was excited by the upward wavenumber 2 planetary waves, which were mainly related to the Ural and Alaska blockings (Rao J et al, 2018).…”

Stratospheric influence on North Atlantic marine cold air outbreaks following sudden stratospheric warming events

“…The stratosphere can have a significant impact on surface weather in the North Atlantic and Europe. This has dominantly been investigated with respect to cold temperature extremes over land, where cold air outbreak frequency has been linked to the strength of the stratospheric polar vortex (Thompson et al, 2002;Kolstad et al, 2010;King et al, 2019). Extreme changes in the stratospheric polar vortex, such as sudden stratospheric warming (SSW) events, often lead to a negative signature of the North Atlantic Oscillation (NAO; e.g.…”