Jet-Streak Dynamics

Background
Journal Articles
Conference Preprints (with figures)
Conference Abstracts
MS Thesis
PhD Prospectus
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Background

Jet streaks are defined as localised wind speed maxima along the jet stream. They are a common feature of the extratropical atmosphere, particularly at the level of the tropopause, and have assumed a prominent role in synoptic meteorology, largely in recognition of their association with cyclogenesis and severe weather. However, while there are a number of conceptual models relating jet streaks to vertical motion, little attention appears to have been devoted to the dynamical treatment of these features. Questions arise as to how jet streaks may be represented dynamically, and hence how they may be studied using a body of idealised conceptual and numerical models.

There appears to be a decent amount of evidence from observations that at least some jet streaks result from the superposition of monopolar and dipolar vortices of mesoscale dimensions (vortex radius ~350-500 km) with the enhanced potential vorticity gradients that constitute the extratropical tropopause. The figure below is one such example - click on the image to view the full size version and the caption. You will notice that many of the jet streaks seen on this map are found in conjunction with localised "blobs" of potential vorticity (note for example the jet streak over North America). These blobs typically possess numerous closed contours of PV, and correspond to strongly nonlinear mesoscale vortices. In the relative vorticity field, a dipolar structure (i.e., cyclonic-anticyclonic couples) often can be seen in association with these PV blobs, although this field may also be monopolar.

Vortices are fundamental features of fluid mechanics, and in association with the large-scale background flow in the atmosphere, they may be considered to "induce" jet streaks. This hypothesis provides the foundation for the work I have been undertaking for my MS and PhD degrees, in which I have employed elements of the theory of vortex dynamics in conjunction with some idealised models to gain some insight into the structure and behaviour of jet streaks in extratropical regions.

In January 1997 I presented my MS thesis entitled ``Analytical and Numerical Modelling of Jet-Streak Dynamics'', and at present I am working on my PhD which has the tentative title of ``Coherent Structures in the Extratropical Atmosphere: A Dynamical Interpretation of Jet Streaks.''

Below you will find all the documents that I have written over the past few years, including conference abstracts and preprints, and placed them here either as HTML or as postscript documents. For further information, feel free to send me mail at cunning@atmos.albany.edu.

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Journal Articles

Below you can download an article I submitted on 16 August 1999 to the Quarterly Journal of the Royal Meteorological Society that describes the results of my MS thesis.
"Analytical and numerical modelling of jet streaks: Barotropic dynamics" (Text) (Figures)
Here is the abstract in html.

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Conference Preprints (with figures)

8th Conference on Mesoscale Processes. Boulder, CO, June 1999. (Postscript only)
12th Conference on Atmospheric and Oceanic Fluid Dynamics. New York, NY, June 1999. (Postscript only)
IUTAM/IUGG Developments in Geophysical Turbulence. Boulder, CO, June 1998.
11th Conference on Atmospheric and Oceanic Fluid Dynamics. Tacoma, WA, June 1997.
7th Conference on Mesoscale Processes. Reading, UK, September 1996.

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Conference Abstracts

8th Conference on Mesoscale Processes. Boulder, CO, June 1999.
12th Conference on Atmospheric and Oceanic Fluid Dynamics. New York, NY, June 1999.
33rd Annual CMOS Congress. Montreal, PQ, June 1999.
IUTAM/IUGG Developments in Geophysical Turbulence. Boulder, CO, June 1998.
10th Extratropical Cyclone Workshop. Val Morin, Quebec, September 1997.
IAMAS/IAPSO Joint Assemblies. Melbourne, Australia, July 1997.
11th Conference on Atmospheric and Oceanic Fluid Dynamics. Tacoma, WA, June 1997.
7th Conference on Mesoscale Processes. Reading, UK, September 1996.
9th Extratropical Cyclone Workshop. Monterey, CA, December 1995.

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MS Thesis

``Analytical and Numerical Modelling of Jet-Streak Dynamics''

Abstract

The following files contain my MS Thesis in its entirety. All figures are contained within, and are located at the end of each chapter. If you do happen to read any of this thesis, I would be pleased to hear any questions or comments.

File 1 - Title page, Abstract, Contents, Introduction (pp. 1-16).
File 2 - Chapter 2 (pp. 17-55).
File 3 - Chapter 3 (pp. 56-88).
File 4 - Chapter 4 (pp. 89-129).
File 5 - Summary & Discussion, References, Appendix (pp. 130-150).

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PhD Prospectus

``Coherent Structures in the Extratropical Atmosphere: A Dynamical Interpretation of Jet Streaks''

Abstract

This prospectus was defended successfully in April 1998, and contains a thorough overview of the work I will be undertaking over the next few years, and perhaps beyond. I would be very interested to hear any comments on this proposed research.
The following two files contain the complete text and the figures, respectively, in postscript form.

Text
Figures

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Phil Cunningham
cunning@atmos.albany.edu