[Atmosdyn] atmosdyn: weekly summary

[Andres, Heather]

Hi everyone.

Today we discussed Rossby waves as waves with potential vorticity as a
restoring agent.  We looked at the assumptions required to obtain these
solutions and their implications.

1.  Dispersion relation depends on the wavenumber, so they do not travel as
a wave packet, but split according to their wave number.

2.  The background flow exactly balances the phase speed to produce
standing waves with a wavenumber 3ish pattern in current mid-latitudes
(i.e. U~30m/s)

3.  Phase speeds tend to be easterly for low wave numbers and westerly for
high wave numbers.  The group velocity is westerly in all cases.

Outstanding questions:
1.  What does it mean to have a non-zero group velocity for a standing wave?
2.  What determines the balance between the three potential vorticity terms
when responding to a perturbation?  For example, for zonal flow over the
Rockies, what determines how much of the correction is associated with
changes to relative vorticity and changes to latitudinal position?

Next week, Taimaz will be presenting the Eliassen-Palm flux.  THis is a
start to wave -mean flow interactions in Chapter 7.2 of Vallis.  An
electronic version of Lev's preferred textbook, Cushman-Roisin, has been
found.  Ryan, can you make that available to people?  We'll use that as a
second place to work from in our future discussions.  It's less
mathematical and more physical.

Heather

-- 
********************************************************
Dr. Heather Andres
Post-doctoral Research Fellow
Physics and Physical Oceanography
Memorial University of Newfoundland
St. John's, CANADA
(709)864-8846
*********************************************************
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