The dynamics of NAO teleconnection pattern growth and decay

Feldstein, Steven B.

doi:10.1256/qj.02.76

Cited by 254 publications

(244 citation statements)

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“…Feldstein (2003), Benedict et al (2004), Franzke et al (2004), and Riviere and Orlanski (2007) found that the NAO is breaking and the low-frequency/high-frequency eddies' breaking plays a fundamental role in the transition of the NAO phase. Our results here show that not only…”

Section: Discussionmentioning

confidence: 99%

Northern hemisphere storm tracks in strong AO anomaly winters

Nie

Wang

Yang

et al. 2008

Atmospheric Science Letters

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Northern Hemisphere winter 300 hPa storm tracks/baroclinic waves and their energetics during strong Arctic Oscillation (AO) anomaly events are investigated. It is shown that during strong positive AO anomaly winters, the Atlantic storm track intensifies significantly and shifts northward and far downstream while Pacific storm track extends westward. Baroclinic waves over the Atlantic propagate along central North Atlantic during strong negative AO anomaly winters while during strong positive AO anomaly winters, waves over the Atlantic split into two branches. Distributions of the kinetic energy and energy conversions of different spatial scale over the storm track regions assume different characteristics for different AO phases.

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Section: Discussionmentioning

confidence: 99%

Northern hemisphere storm tracks in strong AO anomaly winters

Nie

Wang

Yang

et al. 2008

Atmospheric Science Letters

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“…Finally, Orsolini et al (2008) have recently analyzed the formation and life cyclone of the Aleutian-Icelandic Low Seesaw in an atmospheric GCM with a well resolved stratosphere, and they identified a clear extension of this Seesaw into the stratosphere, where its presence modulates the polar night jet intensity. Feldstein (2002Feldstein ( , 2003 investigated the nature of both PNA and NAO modes and concluded that the most important difference is that while PNA life cycle is dominated by linear processes, the variability of the NAO is dominated by nonlinear processes. Further, and unlike the PNA, the NAO may be interpreted as a forced phenomenon (Feldstein 2003).…”

Section: Introductionmentioning

confidence: 99%

The variable link between PNA and NAO in observations and in multi-century CGCM simulations

2010

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The link between the Pacific/North American pattern (PNA) and the North Atlantic Oscillation (NAO) is investigated in reanalysis data (NCEP, ERA40) and multicentury CGCM runs for present day climate using three versions of the ECHAM model. PNA and NAO patterns and indices are determined via rotated principal component analysis on monthly mean 500 hPa geopotential height fields using the varimax criteria. On average, the multicentury CGCM simulations show a significant anti-correlation between PNA and NAO. Further, multi-decadal periods with significantly enhanced (high anti-correlation, active phase) or weakened (low correlations, inactive phase) coupling are found in all CGCMs. In the simulated active phases, the storm track activity near Newfoundland has a stronger link with the PNA variability than during the inactive phases. On average, the reanalysis datasets show no significant anti-correlation between PNA and NAO indices, but during the sub-period 1973-1994 a significant anti-correlation is detected, suggesting that the present climate could correspond to an inactive period as detected in the CGCMs. An analysis of possible physical mechanisms suggests that the link between the patterns is established by the baroclinic waves forming the North Atlantic storm track. The geopotential height anomalies associated with negative PNA phases induce an increased advection of warm and moist air from the Gulf of Mexico and cold air from Canada. Both types of advection contribute to increase baroclinicity over eastern North America and also to increase the low level latent heat content of the warm air masses. Thus, growth conditions for eddies at the entrance of the North Atlantic storm track are enhanced. Considering the average temporal development during winter for the CGCM, results show an enhanced Newfoundland storm track maximum in the early winter for negative PNA, followed by a downstream enhancement of the Atlantic storm track in the subsequent months. In active (passive) phases, this seasonal development is enhanced (suppressed). As the storm track over the central and eastern Atlantic is closely related to the NAO variability, this development can be explained by the shift of the NAO index to more positive values.

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“…The NAO not only affects the surface temperature and the occurrence of storms and precipitation over the Europe, but also influences the global climate (Hurrell 1995a). Although the NAO is found to exhibit remarkable decadal variability (Hurrell 1995a;Häkkinen 2000), the inherent time scale of the NAO events is actually about two weeks and the synopticscale eddies may be the dynamical driver of the NAO (Feldstein 2003). In a previous paper (Luo et al 2007, hereafter LLW), a weakly nonlinear model is proposed to account for the interaction between preexisting planetary-scale and synoptic-scale waves leads to an NAO event, a zonally localized dipole mode (Hurrell 1995b;Vallis et al 2004;Cash et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Eddy-Driven Low-Frequency Dipole Modes. Part II: Free Mode Characteristics of NAO and Diagnostic Study

Luo

Gong

Lupo

2007

Journal of the Atmospheric Sciences

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Through calculating the scatter diagrams of the streamfunction ( P or T ) versus potential vorticity (PV) (q P or q T ), where P and T are the planetary-scale streamfunction and total streamfunction, respectively, and using a weakly nonlinear NAO model proposed in Part I of this paper, it is suggested that negative-and positive-phase NAO events may approximately correspond to free modes even though driven by synopticscale eddies. In a planetary-scale field, the q P ( P ) scatter diagram of an NAO event exhibits a linear multivalued functional relationship in a narrow region for the negative phase, but exhibits a linear singlevalued functional relationship during the positive phase. It was also found that there is no steepening of the slope of the main straight line in the q P ( P ) scatter diagrams for two phases of the NAO event. Instead, the slope of the straight line in the scatterplots is time independent throughout the life cycle of the NAO event.However, when synoptic-scale eddies are included in the streamfunction field, the q T ( T ) scatter diagram of the negative-phase NAO event shows a trend toward steepening during the intensification phase, and this tendency reverses during the decay phase. During the positive NAO phase the slope of the q t ( T ) scatter diagram shoals during the intensification phase and then steepens during the decay phase. Thus, it appears that the steepening and shoaling of the scatter diagrams of the streamfunction versus PV for the negativeand positive-phase NAO events are attributed to the effect of synoptic-scale eddies that force NAO events to form. Diagnostic studies using both composite and unfiltered fields of observed NAO events are presented to confirm these conclusions.

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The dynamics of NAO teleconnection pattern growth and decay

Cited by 254 publications

References 42 publications

Northern hemisphere storm tracks in strong AO anomaly winters

Northern hemisphere storm tracks in strong AO anomaly winters

The variable link between PNA and NAO in observations and in multi-century CGCM simulations

Dynamics of Eddy-Driven Low-Frequency Dipole Modes. Part II: Free Mode Characteristics of NAO and Diagnostic Study

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