Name:			Aime' Fournier
Citizenship:		USA
Organization:		NCAR & U MD CCMPS Meteorology
Mailing Address:	NCAR
			POB 3000
			Boulder, CO 80307-3000
Tel. No.:		303 497 1614
Fax No.:		303 497 1700
E-Mail:			fournier@ucar.edu

Title and abstract of presentation:

The polar vortex as an initial-value test case for the spherical 
primitive equations

A. Fournier, L. M. Polvani, R. Saravanan and M. A. Taylor

Three-dimensional simulation of breaking Rossby waves on the polar 
night vortex is proposed and demonstrated as an initial-value test case 
for the spherical primitive equations.  This test case exhibits more 
complex structure and dimensionality than the tests of Williamson et 
al., and addresses forecast issues, unlike the climatological tests of 
Held and Suarez and Boer and Denis.  The present test is offered as a 
supplement to these.

Balanced axisymmetric-vortex initialization with step-function-like 
absolute vorticity follows the design of Polvani and Saravanan 
(http://www.columbia.edu/~lmp/3Dpv_submitted.ps.gz, submitted).
Pulsed and steadily-increasing surface-geopotential forcings of various 
amplitudes and single zonal wavenumbers are used to instigate upwardly 
propagating Rossby waves.  Spurious reflection is prevented by a sponge 
layer near the model top, including Rayleigh damping of eddy velocity 
and Newton damping of thermal anomalies.

Results are presented for the Community Climate Model 2 Dynamical Core 
at resolutions up to T85 on 48 levels.  Isosurfaces of Scaled Potential 
Vorticity exhibit complex dynamical features including a primary PV 
tongue, and a secondary instability causing roll-up into a ring of 5 
smaller sub-vortices.  These features converge, and PV gradients 
steepen, as resolution is increased.  The PV-tongue-tip position, number 
of sub-vortices, zonal velocity profile at day 25 and other 
quantitative measures are proposed as specific modeling-accuracy goals 
of this test case.

Since no analytical solution is available and it is not feasible to run
CCM2DC past T85, results are also presented using a totally different 
dynamical core, the Spectral Element Atmospheric Model 
(http://www.scd.ucar.edu/css/staff/taylor/doe/seam.html, presented at 
PDE's On The Sphere 1998).  Results from SEAM verify the CCM2DC results 
and indicate convergence up to T181 (approximately equivalent to 70 km 
horizontal resolution), with 200 levels.

Special requirements or comments:
To be presented by AF.  Two transparency projectors would be 
preferable, if possible.