Diagnosis of Frontal Instabilities over the Southern Ocean

Patoux, Jérôme; Hakim, Gregory J.; Brown, Robert A.

doi:10.1175/mrw2883.1

Cited by 15 publications

(4 citation statements)

References 41 publications

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“…Scatterometers have revolutionized our view of the surface wind field over the world ocean [ Milliff et al , 2002; Liu , 2002]. We now better understand its interactions with oceanic fronts [ O'Neill et al , 2005; Samelson et al , 2006], the air‐sea interactions in the intertropical convergence zone [ Chelton et al , 2001; Chelton , 2005], the effects of baroclinicity on the marine boundary layer [ Foster et al , 1999], and the role of the environmental flow in the development of frontal waves [ Patoux et al , 2005] among many applications. Levy and Brown [1991] and Levy [1994] demonstrated the impact of the early Seasat scatterometer on our view of the Southern Hemisphere synoptic weather.…”

Section: Introductionmentioning

confidence: 99%

Satellite‐based midlatitude cyclone statistics over the Southern Ocean: 1. Scatterometer‐derived pressure fields and storm tracking

Patoux

Yuan

2009

J. Geophys. Res.

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[1] A wavelet-based method is described for incorporating swaths of surface pressure derived from scatterometer measurements into surface pressure analyses obtained from the European Centre for Medium-range Weather Forecasts (ECMWF). The resulting modified pressure fields are used to identify low-pressure centers over the Southern Ocean and to build statistics of midlatitude cyclones during 7 years of the SeaWinds-on-QuikSCAT operational period (July 1999 to June 2006. The impact of the scatterometer-derived pressure swaths is assessed with a statistical analysis of cyclone characteristics (central pressure, radius, depth) performed in parallel on the ECMWF and on the modified pressure fields. More low-pressure centers (5-10% depending on the season) are identified with the modified pressure fields, in particular incipient lows captured earlier than ECMWF and more short-lived mesoscale cyclones (with a life span less than 4 days). The cyclones identified with the modified pressure fields are characterized by lower central pressure and tighter isobars on average. A parallel spectral analysis reveals $1% additional energy at scales less than 2000 km in the modified pressure fields.Citation: Patoux, J., X. Yuan, and C. Li (2009), Satellite-based midlatitude cyclone statistics over the Southern Ocean: 1. Scatterometer-derived pressure fields and storm tracking,

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Section: Introductionmentioning

confidence: 99%

Satellite‐based midlatitude cyclone statistics over the Southern Ocean: 1. Scatterometer‐derived pressure fields and storm tracking

Patoux

Yuan

2009

J. Geophys. Res.

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“…The deformation-strain rate is varied between 0.6 × 10 −5 s −1 and 1.4 × 10 −5 s −1 . Values of environmental deformation-strain rate for observed frontal-wave cases typically lie within this range, or are weaker (as determined using the domain-independent vorticityand-divergence-attribution method of Thorpe (1994a, 1994b) by Renfrew et al (1997), Rivals et al Chaboureau and Thorpe (1999) and Patoux et al (2005)). Weaker deformation strains failed to trigger frontal convection in the model within a reasonable time period.…”

Section: Model Simulationsmentioning

confidence: 95%

The impact of deformation strain on the formation of banded clouds in idealized modelling experiments

Gray

Dacre

2008

Quart J Royal Meteoro Soc

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Experiments are performed using an idealized version of an operational forecast model to determine the impact on banded frontal clouds of the strength of deformational forcing, low-level baroclinicity, and model representation of convection. Line convection is initiated along the front, and slantwise bands extend from the top of the line-convection elements into the cold air. This banding is attributed primarily to M adjustment. The cross-frontal spreading of the cold pool generated by the line convection leads to further triggering of upright convection in the cold air that feeds into these slantwise bands. Secondary low-level bands form later in the simulations; these are attributed to the release of conditional symmetric instability. Enhanced deformation strain leads to earlier onset of convection and more coherent line convection. A stronger cold pool is generated, but its speed is reduced relative to that seen in experiments with weaker deformational strain, because of inhibition by the strain field. Enhanced low-level baroclinicity leads to the generation of more inertial instability by line convection (for a given capping height of convection), and consequently greater strength of the slantwise circulations formed by M adjustment. These conclusions are based on experiments without a convective-parametrization scheme. Experiments using the standard or a modified scheme for this model demonstrate known problems with the use of this scheme at the awkward 4 km grid length used in these simulations.

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“…There are numerous case-study analyses and climatological compilations that relate to aspects of such wave trains (Ford and Kent Moore, 1990;Appenzeller and Davies, 1992;Fehlmann and Davies, 1999;Zhang et al, 1999;Parker, 1998;Patoux et al, 2005;Boettcher and Wernli, 2011;Simmonds et al, 2012;Schemm and Sprenger, 2015). The objective in this subsection is merely to introduce and illustrate some characteristic features of frontal wave-trains as they pertain to the present study.…”

Section: Features Of a Nascent Frontal Wave-trainmentioning

confidence: 98%

Eady edge waves, frontal wave-trains and type-B cyclogenesis

Davies

2021

Tellus A: Dynamic Meteorology and Oceanography

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Eady edge waves (EEWs) propagate on surface baroclinic zones and they resemble synoptic and sub-synoptic scale frontal wave-trains. The wave-trains are frequently depicted on surface charts, and occur per se on a front with a local baroclinicity extremum. The possible linkage of EEWs to frontal waves is explored within the framework of so-called 'surface quasi-geostrophic dynamics' by establishing the properties of free and forced EEWs propagating on an ambient flow comprising a laterally confined baroclinic zone. It is shown that the dispersion properties of the free EEWs modes are influenced significantly both by the zone's baroclinicity extremum and by key features that are akin to those of cold and warm fronts. In particular the larger-scale waves are nondispersive and a local wave-packet can retain coherency, the leading modes on a pseudo-cold front possess a phase speed related to the baroclinicity extremum, whereas waves on a pseudowarm front propagate in the reverse direction. Also theoretical considerations demonstrate that forced modes can undergo resonant secular growth. It is further shown that transient or sustained forcing of a front by an upper-tropospheric potential vorticity anomaly (sic. short-wave trough) can serve to instigate features akin to frontal wave-trains and type-B cyclogenesis. More generally the study hints at the significance for NWP of a front's structure and its dispersion properties, and that an element of predictability is introduced by the latter features due to dynamical scale selection.

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Diagnosis of Frontal Instabilities over the Southern Ocean

Cited by 15 publications

References 41 publications

Satellite‐based midlatitude cyclone statistics over the Southern Ocean: 1. Scatterometer‐derived pressure fields and storm tracking

Satellite‐based midlatitude cyclone statistics over the Southern Ocean: 1. Scatterometer‐derived pressure fields and storm tracking

The impact of deformation strain on the formation of banded clouds in idealized modelling experiments

Eady edge waves, frontal wave-trains and type-B cyclogenesis

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