The Influence of Stratospheric Vortex Displacements and Splits on Surface Climate

Abstract

A strong link exists between stratospheric variability and anomalous weather patterns at the earth's surface. Specifically, during extreme variability of the Arctic polar vortex termed a ''weak vortex event,'' anomalies can descend from the upper stratosphere to the surface on time scales of weeks. Subsequently the outbreak of cold-air events have been noted in high northern latitudes, as well as a quadrupole pattern in surface temperature over the Atlantic and western European sectors, but it is currently not understood why certain events descend to the surface while others do not. This study compares a new classification technique of weak vortex events, based on the distribution of potential vorticity, with that of an existing technique and demonstrates that the subdivision of such events into vortex displacements and vortex splits has important implications for tropospheric weather patterns on weekly to monthly time scales. Using reanalysis data it is found that vortex splitting events are correlated with surface weather and lead to positive temperature anomalies over eastern North America of more than 1.5 K, and negative anomalies over Eurasia of up to 23 K. Associated with this is an increase in high-latitude blocking in both the Atlantic and Pacific sectors and a decrease in European blocking. The corresponding signals are weaker during displacement events, although ultimately they are shown to be related to cold-air outbreaks over North America. Because of the importance of stratospheretroposphere coupling for seasonal climate predictability, identifying the type of stratospheric variability in order to capture the correct surface response will be necessary.

Observations of stratospheric sudden warmings in Earth rotation variations

“…We did not find statistically significant differences in compositing between vortex-splitting or displacement events in either the 2 or ΔLOD anomalies, even though previous studies have shown significant differences in the precursor anomaly patterns associated with vortex splits and displacements [Martius et al, 2009;Mitchell et al, 2012]. The difference in the Earth rotation signature of these types of events and a possible…”

“…The surface pressure signals preceding SSWs differ between vortex-displacement and vortex-splitting events, with vortex displacements more strongly associated with a low-pressure anomaly over North America, a high-pressure anomaly over Western Europe, and North Atlantic blocking, and vortex splits associated with high-pressure anomalies over the North Pacific and Siberia, a low-pressure anomaly over the North Atlantic, and North Pacific blocking with or without Atlantic blocking [Martius et al, 2009;Mitchell et al, 2012]. The surface anomaly pattern preceding vortex displacements is more closely associated with a wave 1 pressure anomaly (which would result in a negative M 2 anomaly), whereas vortex splits can be preceded by a wave 1 or wave 2 anomaly [Bancalá et al, 2012;Martius et al, 2009] (a wave 2 anomaly results in no net M 2 excitation), though this relationship seems to be strongly modulated by the phase of ENSO [Barriopedro and Calvo, 2014].…”

Comparison of co‐located independent ground‐based middle atmospheric wind and temperature measurements with numerical weather prediction models

“…In particular, improvements of the microbarom predictions would require more accurate source and propagation models [e.g., Landès et al, 2014]. With the increasing number of IMS and other infrasonic arrays deployed around the globe, more systematic studies using historical infrasound data set and state-of-the-art reanalysis systems could provide useful information on the polar vortex structure and the longer-term influences of SSWs on the troposphere [e.g., Charlton-Perez et al, 2007;Mitchell et al, 2013;Smets and Evers, 2014].…”

Weakening of the stratospheric polar vortex by Arctic sea-ice loss

“…20). SSW events are often followed by a negative phase of the AO at the surface with a time lag of 1 or 2 months [21][22][23] . This indicates that understanding possible contributors to recent stratospheric variability, which may include cryospheric changes 24 , is critical for the better understanding of the surface climate variability in the recent past.…”