scholarly journals On the role of Rossby wave breaking in the quasi‐biennial modulation of the stratospheric polar vortex during boreal winter

2020 ◽  
Vol 146 (729) ◽  
pp. 1939-1959
Author(s):  
Hua Lu ◽  
Matthew H. Hitchman ◽  
Lesley J. Gray ◽  
James A. Anstey ◽  
Scott M. Osprey
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Polar Vortex ◽  
Boreal Winter ◽  
Stratospheric Polar Vortex ◽  
Rossby Wave Breaking

scholarly journals Rossby Wave Breaking and Transient Eddy Forcing during Euro-Atlantic Circulation Regimes

2017 ◽  
Vol 74 (6) ◽  
pp. 1735-1755 ◽  
Author(s):  
Erik T. Swenson ◽  
David M. Straus
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Ocean Model ◽  
Heat Fluxes ◽  
Boreal Winter ◽  
Transient Eddy ◽  
Flux Divergence ◽  
Western Atlantic ◽  
Rossby Wave Breaking

Abstract The occurrence of boreal winter Rossby wave breaking (RWB) along with the quantitative role of synoptic transient eddy momentum and heat fluxes directly associated with RWB are examined during the development of Euro-Atlantic circulation regimes using ERA-Interim. Results are compared to those from seasonal reforecasts made using the Integrated Forecast System model of ECWMF coupled to the NEMO ocean model. The development of both Scandinavian blocking and the Atlantic ridge is directly coincident with anticyclonic wave breaking (AWB); however, the associated transient eddy fluxes do not contribute to (and, in fact, oppose) ridge growth, as indicated by the local Eliassen–Palm (EP) flux divergence. Evidently, other factors drive development, and it appears that wave breaking assists more with ridge decay. The growth of the North Atlantic Oscillation (NAO) in its positive phase is independent of RWB in the western Atlantic but strongly linked to AWB farther downstream. During AWB, the equatorward flux of cold air at upper levels contributes to a westerly tendency just as much as the poleward flux of momentum. The growth of the negative phase of the NAO is almost entirely related to cyclonic wave breaking (CWB), during which equatorward momentum flux dominates at jet level, yet low-level heat fluxes dominate below. The reforecasts yield realistic frequencies of CWB and AWB during different regimes, as well as realistic estimates of their roles during development. However, a slightly weaker role of RWB is simulated, generally consistent with a weaker anomalous circulation.

scholarly journals Isentropic Transport within the Antarctic Polar-Night Vortex: Rossby Wave Breaking Evidence and Lagrangian Structures

2013 ◽  
Vol 70 (9) ◽  
pp. 2982-3001 ◽  
Author(s):  
Alvaro de la Cámara ◽  
Carlos R. Mechoso ◽  
Ana M. Mancho ◽  
Encarna Serrano ◽  
Kayo Ide
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Invariant Manifolds ◽  
Chaotic Behavior ◽  
Polar Vortex ◽  
Arc Length ◽  
Polar Night ◽  
Stratospheric Polar Vortex ◽  
Rossby Wave Breaking ◽  
The Antarctic

Abstract The trajectories in the lower stratosphere of isopycnic balloons released from Antarctica by Vorcore and Concordiasi field campaigns during the southern springs of 2005 and 2010 showed events of latitudinal transport inside the stratospheric polar vortex, both away from and toward the poleward flank of the polar-night jet. The present paper applies trajectory-based diagnostic techniques to examine mechanisms at work during such events. Reverse domain-filling calculations of potential vorticity (PV) fields from the ECMWF Interim Re-Analysis (ERA-Interim) dataset during the events show irreversible filamentation of the PV fields in the inner side of the polar-night jet, which is a signature of planetary (Rossby) wave breaking. Balloon motions during the events are fairly consistent with the PV filaments. Events of both large (~15° of arc length) and small (~5° of arc length) balloon displacements from the vortex edge are associated, respectively, with deep and shallow penetration into the core of the elongated PV contours. Additionally, the Lagrangian descriptor M is applied to study the configuration of Lagrangian structures during the events. Breaking Rossby waves inside the vortex lead to the presence of hyperbolic points. The geometric configuration of the invariant manifolds associated with the hyperbolic trajectories helps to understand the apparent chaotic behavior of balloons' motions and to identify and analyze balloon transport events not captured by reverse domain-filling calculations. The Antarctic polar vortex edge is an effective barrier to air parcel crossings. Rossby wave breaking inside the vortex, however, can contribute to tracer mixing inside the vortex and to occasional air crossings of the edge.

Representation of the Scandinavia-Greenland Pattern and its Relationship with the Polar Vortex in S2S Models

2021 ◽  
Author(s):  
Simon Lee ◽  
Andrew Charlton-Perez ◽  
Jason Furtado ◽  
Steven Woolnough
Keyword(s):  
Heat Flux ◽  
Wave Breaking ◽  
Polar Vortex ◽  
Boreal Winter ◽  
Stratospheric Polar Vortex ◽  
Rossby Wave Breaking ◽  
The North ◽  
Eddy Heat Flux ◽  
Vertically Propagating ◽  
The North Atlantic Oscillation

<p>The strength of the stratospheric polar vortex is a key contributor to subseasonal prediction during boreal winter. Anomalously weak polar vortex events can be induced by enhanced vertically propagating Rossby waves from the troposphere, driven by blocking and wave breaking. Here, we analyse a tropospheric pattern—the Scandinavia–Greenland (S–G) pattern—associated with both processes. The S–G pattern is defined as the second empirical orthogonal function (EOF) of mean sea‐level pressure in the northeast Atlantic. The first EOF is a zonal pattern resembling the North Atlantic Oscillation. We show that the S–G pattern is associated with a transient amplification of planetary wavenumber 2 and meridional eddy heat flux, followed by the onset of a persistently weakened polar vortex. We then analyse 10 different models from the S2S database, finding that, while all models represent the structure of the S–G pattern well, some models have a zonal bias with more than the observed variability in their first EOF, and accordingly less in their second EOF. This bias is largest in the models with the lowest resolution, and consistent with biases in blocking and Rossby wave breaking in these models. Skill in predicting the S–G pattern is not high beyond week 2 in any model, in contrast to the zonal pattern. We find that the relationship between the S–G pattern, enhanced eddy heat flux in the stratosphere, and a weakened polar vortex is initially well represented, but decays significantly with lead time in most S2S models. Our results motivate improved representation of the S–G pattern and its stratospheric response at longer lead times for improved subseasonal prediction of the stratospheric polar vortex.</p>

scholarly journals Tropospheric Rossby Wave Breaking and Variability of the Latitude of the Eddy-Driven Jet

2014 ◽  
Vol 27 (18) ◽  
pp. 7069-7085 ◽  
Author(s):  
Chaim I. Garfinkel ◽  
Darryn W. Waugh
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
General Circulation ◽  
Polar Vortex ◽  
Circulation Model ◽  
Internal Variability ◽  
Tropospheric Temperature ◽  
Stratospheric Polar Vortex ◽  
Rossby Wave Breaking ◽  
Ultimate Cause

Abstract A dry general circulation model is used to investigate the connections between Rossby wave breaking and the latitude of the midlatitude tropospheric eddy-driven jet. An ensemble of experiments is constructed in which the jet latitude is influenced by a midlatitude tropospheric temperature anomaly that resembles observed climate change and by the imposition of a stratospheric polar vortex, and the distribution of Rossby wave breaking frequency is examined for each experiment. The shift in wave breaking per degree latitude of jet shift is then compared for three different sources of jet movement: the tropospheric baroclinic forcing imposed in midlatitudes, the imposition of a stratospheric polar vortex, and the internal variability of the midlatitude eddy-driven jet. It is demonstrated that all three sources of jet movement produce a similar change in Rossby wave breaking frequency per degree of jet shift. Hence, it is difficult (if not impossible) to isolate the ultimate cause behind the shift in Rossby wave breaking in response to the two external forcings.

scholarly journals Quantifying Asymmetric Wave Breaking and Two-Way Transport

2004 ◽  
Vol 61 (22) ◽  
pp. 2735-2748 ◽  
Author(s):  
Noboru Nakamura
Keyword(s):  
Wave Breaking ◽  
Polar Vortex ◽  
Effective Diffusivity ◽  
The Other ◽  
Stratospheric Polar Vortex ◽  
Air Masses ◽  
Rossby Wave Breaking ◽  
Advection Diffusion Equation ◽  
Extratropical Tropopause ◽  
Asymmetric Wave

Abstract Effective diffusivity calculated from a scalar field that obeys the advection–diffusion equation has proved useful for estimating the permeability of unsteady boundaries of air masses such as the edge of the stratospheric polar vortex and the extratropical tropopause. However, the method does not discriminate the direction of transport—whereas some material crosses the boundary from one side to the other, some material does so in the other direction—yet the extant method concerns only the net transport. In this paper, the diagnostic is extended to allow partitioning of fluxes of mass and tracer into opposing directions. This is accomplished by discriminating the regions of “inward” and “outward” wave breaking with the local curvature of the tracer field. The utility of the new method is demonstrated for nonlinear Kelvin– Helmholtz instability and Rossby wave breaking in the stratosphere using a numerically generated tracer. The method successfully quantifies two-way transport and hence the direction of wave breaking—the predominantly equatorward breaking of Rossby waves in the extratropical middle stratosphere, for example. Isolated episodes of mixing are identified well, particularly by the mass flux that primarily arises from the tracer filaments. Comparison of different transport schemes suggests that the results are reasonably robust under a varying subgrid representation of the model.

scholarly journals Modeling Rossby Wave Breaking in the Southern Spring Stratosphere

2015 ◽  
Vol 73 (1) ◽  
pp. 393-406 ◽  
Author(s):  
Anirban Guha ◽  
Carlos R. Mechoso ◽  
Celal S. Konor ◽  
Ross P. Heikes
Keyword(s):  
Velocity Profile ◽  
Rossby Wave ◽  
Traveling Wave ◽  
Wave Breaking ◽  
Invariant Manifolds ◽  
Water System ◽  
Lagrangian Analysis ◽  
Stratospheric Polar Vortex ◽  
Rossby Wave Breaking ◽  
Zonal Wavenumber

Abstract Rossby wave breaking (RWB) plays a central role in the evolution of stratospheric flows. The generation and evolution of RWB is examined in the simple dynamical framework of a one-layer shallow-water system on a sphere. The initial condition represents a realistic, zonally symmetric velocity profile corresponding to the springtime southern stratosphere. Single zonal wavenumber Rossby waves, which are either stationary or traveling zonally with realistic speeds, are superimposed on the initial velocity profile. Particular attention is placed on the Lagrangian structures associated with RWB. The Lagrangian analysis is based on the calculation of trajectories and the application of a diagnostic tool known as the “M” function. Hyperbolic trajectories (HTs), produced by the transverse intersections of stable and unstable invariant manifolds, may yield chaotic saddles in M. Previous studies associated HTs with “cat’s eyes” generated by planetary wave breaking at the critical levels. HTs, and hence RWB, are found both outside and inside the stratospheric polar vortex (SPV). Significant findings are as follows: (i) stationary forcing produces HTs only outside of the SPV and (ii) eastward-traveling wave forcing can produce HTs both outside and inside of the SPV. In either case, HTs appear at or near the critical latitudes. RWB was found to occur inside the SPV even when the forcing was located completely outside. In all cases, the westerly jet remained impermeable throughout the simulations. The results suggest that the HT inside the SPV observed by de la Cámara et al. during the southern spring 2005 was due to RWB of an eastward-traveling wave of wavenumber 1.

Seasonal Influence of the Quasi-Biennial Oscillation on Stratospheric Jets and Rossby Wave Breaking

2009 ◽  
Vol 66 (4) ◽  
pp. 935-946 ◽  
Author(s):  
Matthew H. Hitchman ◽  
Amihan S. Huesmann
Keyword(s):  
Rossby Wave ◽  
Wave Breaking ◽  
Boreal Winter ◽  
Quasi Biennial Oscillation ◽  
Rossby Wave Breaking ◽  
Eastern Hemisphere ◽  
Biennial Oscillation ◽  
Mode A ◽  
Pv Gradient ◽  
Middle Stratosphere

Abstract The influence of the stratospheric quasi-biennial oscillation (QBO) on the polar night jets (PNJs), subtropical easterly jets (SEJs), and associated Rossby wave breaking (RWB) is investigated using global meteorological analyses spanning 10 recent QBO cycles. The seasonal dependence of the descent of the QBO is shown by using five layered shear indices. It is found that the influence of the QBO is distinctive for each combination of QBO phase, season, and hemisphere (NH or SH). The following QBO westerly (W) minus easterly (E) differences in the PNJs were found to be significant at the 97% level: When a QBO W (E) maximum is in the lower stratosphere (∼500 K or ∼50 hPa), the NH winter PNJ is stronger (weaker), in agreement with previous results (mode A). Mode A does not appear to operate in other seasons in the NH besides DJF or in the SH in any season. When a QBO W (E) maximum is in the middle stratosphere (∼700–800 K or ∼10–20 hPa), the PNJ in the SH spring is stronger (weaker), also in agreement with previous results (mode B). It is found that mode B also operates in the NH spring. A third distinctive mode is found during autumn in both hemispheres: a QBO W (E) maximum in the middle stratosphere coincides with a weaker (stronger) PNJ (mode C). The signs of wind anomalies are the same at low and high latitudes for modes A and B, but are opposite for mode C. This sensitive dependence on QBO phase and season is consistent with the nonlinear nature of the interaction between planetary waves and the shape of the seasonal wind structures. During the solstices the meridional circulation associated with QBO connects primarily with the winter hemisphere, whereas during the equinoxes it is more symmetric about the equator. QBO W enhance the equatorial potential vorticity (PV) gradient maximum, but the time-mean maximum may be related to chronic instabilities in the subtropics. The equatorial PV gradient maximum and flanking RWB tend to be more pronounced in the Eastern Hemisphere in stratospheric analyses. When QBO W are in the middle stratosphere, the flanking PV gradient minima (SEJs) are enhanced and RWB is more frequent and symmetric about the equator. When QBO W are in the upper stratosphere, a strong seasonal asymmetry is seen, with enhanced RWB in the summer SEJ, primarily during boreal winter. This is consistent with an upward increase of summer to winter flow and modulation by a strong “first” and weak “second” semiannual oscillation.

scholarly journals The Role of Dynamic Tropopause Rossby Wave Breaking for Synoptic-Scale Buildups in Northern Hemisphere Zonal Available Potential Energy

2019 ◽  
Vol 147 (2) ◽  
pp. 433-455 ◽  
Author(s):  
Kevin A. Bowley ◽  
John R. Gyakum ◽  
Eyad H. Atallah
Keyword(s):  
Potential Energy ◽  
Northern Hemisphere ◽  
Rossby Wave ◽  
North Pacific ◽  
Wave Breaking ◽  
Synoptic Scale ◽  
Rossby Wave Breaking ◽  
The North ◽  
The North Pacific

Abstract Zonal available potential energy AZ measures the magnitude of meridional temperature gradients and static stability of a domain. Here, the role of Northern Hemisphere dynamic tropopause (2.0-PVU surface) Rossby wave breaking (RWB) in supporting an environment facilitating buildups of AZ on synoptic time scales (3–10 days) is examined. RWB occurs when the phase speed of a Rossby wave slows to the advective speed of the atmosphere, resulting in a cyclonic or anticyclonic RWB event (CWB and AWB, respectively). These events have robust dynamic and thermodynamic feedbacks through the depth of the troposphere that can modulate AZ. Significant synoptic-scale buildups in AZ and RWB events are identified from the National Centers for Environmental Prediction Reanalysis-2 dataset from 1979 to 2011 for 20°–85°N. Anomalies in AWB and CWB are assessed seasonally for buildup periods of AZ. Positive anomalies in AWB and negative anomalies in CWB are found for most AZ buildup periods in the North Pacific and North Atlantic basins and attributed to localized poleward shifts in the jet stream. Less frequent west–east dipoles in wave breaking anomalies for each basin are attributed to elongated and contracted regional jet exit regions. Finally, an analysis of long-duration AWB events for winter AZ buildup periods to an anomalously high AZ state is performed using a quasi-Lagrangian grid-shifting technique. North Pacific AWB events are shown to diabatically intensify the North Pacific jet exit region (increasing Northern Hemisphere AZ) through latent heating equatorward of the jet exit and radiative and evaporative cooling poleward of the jet exit.

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