Patterns of Wintertime Jet Stream Variability and Their Relation to the Storm Tracks*

Abstract

A new approach is put forward for defining extratropical teleconnection patterns. The zonal wind field at 250 hPa is analyzed separately in the North Atlantic and North Pacific Ocean sectors during the winter season (December-March). Teleconnectivity of this field is found to be particularly strong. EOF analysis of the zonal wind field yields patterns that (i) are robust with respect to the range of frequencies included in the data, (ii) relate clearly to the position of the climatological-mean jets, and (iii) are broadly consistent with their traditionally defined counterparts in terms of climatic impacts. The patterns are characterized by a northsouth shifting or an extension/retraction of the eddy-driven jet in its exit region and similar changes at the entrance region of the subtropical jet. The patterns also reflect the degree of separation between the subtropical and eddy-driven jets. Atlantic EOFs 1 and 2 are counterparts of the North Atlantic Oscillation (NAO) and eastern Atlantic pattern, respectively, while Pacific EOF 1 is the counterpart of the Pacific-North America (PNA) pattern. Pacific EOF 2, a pattern that has not been previously noted, has a pronounced impact on the jet configuration and precipitation over the western coast of North America. This pattern may be of particular interest for precipitation forecasting applications. Atlantic EOF 1 exhibits a long decorrelation time and strong negative skewness. The relation between these jet variability patterns and the stormtrack variability is examined, including the dynamical interaction between baroclinic waves and the jets. In each sector, the eddy forcing is found to maintain the respective jet anomalies.

How well do state-of-the-art atmosphere-ocean general circulation models reproduce atmospheric teleconnection patterns?

“…Wallace and Gutzler, 1981;Blackmon et al, 1984). This leads Athanasiadis et al (2010) The regression patterns at 500 hPa are very similar to the teleconnection patterns, underlining the close relation of the NAO (EA) patterns to variations in the position (intensity) of the Atlantic atmospheric jet and of the PNA (WP) patterns to variations in the intensity (position) of the Pacific jet. Thus, the four most important teleconnection patterns NAO, EA, PNA and WP are dynamically consistent with the sectoral zonal wind variability patterns.…”

“…Hence, the basic dynamics of the teleconnection patterns is related to the dynamics of jet streams and their variability. It was found by Athanasiadis et al (2010) that the anomaly patterns of the eddy forcing are similar to those of the related jet anomalies, which underlines the crucial role of the atmospheric eddies in maintaining the teleconnection patterns. Most teleconnection patterns appear in the form of 'standing' waves or in the form of NorthÁSouth-orientated dipoles.…”

“…Evidence for such a coupling between the high frequency transient eddies (baroclinic waves) and teleconnection patterns was given already by Lau (1988) and Hartmann (2001, 2003). The co-variability of zonal wind and baroclinic wave activity and their relation to the most dominant teleconnection patterns (NAO, PNA, WP and EA) has been investigated by, for example, Strong and Davis (2008), Athanasiadis et al (2010) and Woollings et al (2010).…”

“…Wallace and Gutzler, 1981;Blackmon et al, 1984;Ambaum et al, 2001;Athanasiadis et al, 2010). Hence, the basic dynamics of the teleconnection patterns is related to the dynamics of jet streams and their variability.…”

Atmospheric Low Frequency Variability: The Examples of the North Atlantic and the Indian Monsoon

“…The positive phase of the EA is associated with above-and below-average surface temperature over Europe and eastern North America respectively. The variability of these modes is usually described by patterns in pressure or geopotential height fields, or wind fields as in Athanasiadis et al (2009). Jet stream shifts are associated with a positive feedback between the mean flow and the transient eddies (eg, Lorenz and Hartmann 2003).…”