Fine-scale layering on the edge of a stratospheric intrusion

Vaughan, G.; Gouget, Hervé; O’Connor, Fiona M.; Wier, D.

doi:10.1016/s1352-2310(00)00482-9

Cited by 8 publications

(8 citation statements)

References 21 publications

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“…Dynamic processes leading to tropopause folding, as a result of cross frontal secondary circulation associated with jet streams in upper level troughs and cutoff lows, are well documented through extensive studies and measurements of folds. They include theoretical studies [ Hoskins and Bretherton , 1972], in situ aircraft measurements [ Danielsen , 1968; Shapiro , 1980], radar/lidar remote sensing techniques [ Browell et al , 1987; Ancellet et al , 1994; Vaughan et al , 2001; Nastrom et al , 1989; Bertin et al , 2001; Rao et al , 2003; Rao and Kirkwood , 2005], satellite measurements [ Wimmers and Moody , 2004] and mesoscale and synoptic‐scale models [ Ebel et al , 1991; Lamarque and Hess , 1994]. These studies addressed various issues related to the tropopause folds, such as characteristics of folds, identification of folds from observational and model data sets, their role in instigating severe weather events, exchange of constituents occurring through the fold boundaries, etc.…”

Section: Introductionmentioning

confidence: 99%

Climatology of tropopause folds over a European Arctic station (Esrange)

2008

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of continuous measurements of threedimensional wind and backscattered signal strength observed with Esrange Radar (ESRAD) have been utilized to study the annual and interannual variation of tropopause folds over an Arctic station. Two typical tropopause fold events (one is associated with a streamer type of system and the other with a cutoff low) are selected and are characterized with the help of synoptic charts and potential vorticity (PV) analysis. Typical characteristics of radar parameters during the passage of folds are identified, such as the sudden rise in the tropopause altitude, high-reflectivity layer sloping downward from the tropopause beneath the jet stream, and intensification of the jet stream. These characteristics are utilized to discern the tropopause fold in the radar data. The climatology of tropopause folds exhibits a pronounced annual cycle with a large number of folds in winter and fewer in summer. The annual cycle of folds is more or less similar in all the years; however, significant interannual variation is observed with winter periods exhibiting maximum interannual variability. The climatology of folds and its annual cycle are compared and contrasted with similar climatological studies available in the literature. The differences in the climatologies are discussed in light of differences in the algorithms and the spatial variability of fold frequency.

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Section: Introductionmentioning

confidence: 99%

Climatology of tropopause folds over a European Arctic station (Esrange)

2008

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“…Extratropical events, such as the Cho et al (1999) tropopause fold discussed below, may approach similar spatial scales, with the important distinction that extratropical layers may be advected isentropically toward the ground, whereas in the Tropics PV layers of stratospheric origin will remain aloft. Smaller-scale events (H ϳ 500 m, L ϳ 50 km) have also been widely studied in the extratropics, such as the relatively thin layers of stratospheric origin observed near the extratropical tropopause, and referred to as ''streamers'' (e.g., Vaughan et al 2001). Also, stratospheric values of PV may be present in dry intrusion air masses of frontal circulations (e.g., Browning 1990).…”

Section: Discussionmentioning

confidence: 99%

Kelvin–Helmholtz Instability of Potential Vorticity Layers: A Route to Mixing

Esler¹,

Polvani²

2004

J. Atmos. Sci.

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The linear and nonlinear dynamics of layers of anomalously high potential vorticity (PV) are studied in detail. It is well known that PV layers are subject to slow, balanced, mixed barotropic-baroclinic instabilities. In this paper, it is shown that, in addition, PV layers are subject to a Kelvin-Helmholtz instability, operating on much smaller spatial and faster temporal scales. For simplicity, spatially infinite layers of uniform anomalous PV are considered. Such layers are characterized by two key parameters: the ratio ⌬q of their anomalous PV to the background PV, and the angle ␣ between the layer and the direction of the ambient stratification gradient (in suitably scaled coordinates). It is found that Kelvin-Helmholtz appears, for certain values of ␣, whenever ⌬q Ͼ 8. Of notable interest is the case of an initially vertical PV layer embedded in a weak ambient shear flow: for sufficiently large ⌬q, once the PV layer is tilted past a critical angle, Kelvin-Helmholtz instability becomes possible. It is argued that the breakdown of PV layers due to a Kelvin-Helmholtz instability induced by ambient shear might be an important systematic mechanism leading to irreversible mixing during stratosphere-troposphere exchange events. This is discussed in the context of an example of Kelvin-Helmholtz instability observed near a tropopause fold.

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“…Recent advances in lidar and radar technology have provided an opportunity to study these features in much more detail (e.g. Holton et al 1995;Vaughan et al 2001). While tropopause folds have been recognized features of atmospheric dynamics for about half a century, it has not proved straightforward to develop a quantification of STE from a climatology of folds.…”

Section: The Tropopausementioning

confidence: 99%

Stratospheric Chemistry and Transport

MacKenzie¹

2003

Handbook of Atmospheric Science

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Fine-scale layering on the edge of a stratospheric intrusion

Cited by 8 publications

References 21 publications

Climatology of tropopause folds over a European Arctic station (Esrange)

Climatology of tropopause folds over a European Arctic station (Esrange)

Kelvin–Helmholtz Instability of Potential Vorticity Layers: A Route to Mixing

Stratospheric Chemistry and Transport

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