Jet-Streak Dynamics

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.