[MITgcm-support] Non-Zero Meridional Velocity Kelvin Wave

[Bertrand Louis Rene Delorme]

Dears,

I am trying to set-up a very simple experiment to generate baroclinic Kelvin waves over an equatorial beta-plane.
My approach so far has been to prescribe initial conditions for U, V, T and ETA based on the normal-mode solutions of the wave.
I managed to get a nice modal structure (both in the vertical and horizontal plane), which propagates without attenuation throughout the simulation.
Here is my problem: in my initial conditions, I set V=0, but right after the first iteration V get non-zero values.
As I am generating a Kelvin wave, I would expect V to stay equal to zero throughout the simulation, if the flow is well-balanced.
In my case, V ends up with an amplitude approximately one order of magnitude lower than U, which is still pretty high.
From the patterns I get in the outputs, it seems that the model is using dV/dy balance dU/dx in the continuity equation.
As I prescribed an initial free-surface, I was expecting W to play this role alone.

My issue can be link to an error in the normal-mode solutions that I use, which I checked carefully without finding any mistakes.
Another possibility would be that it comes from the set-up of my experiment.
I am using a domain centered at the equator with 60x150x200 grid points, with a resolution high enough to resolve the wave.
The only package that I am using is the MNC package, and my data file is pretty simple (see below).

If any of you has an idea of what I should check/test to understand where those non-zero values come from, please let me know.

Best,
Bertrand


&PARM01
sBeta=0.0,
selectCoriMap=1,
f0=0,
beta=2.29E-11,
readBinaryPrec=64,
writeBinaryPrec=64,
&

&PARM02
&

&PARM03
startTime=0.,
endTime=1600000,
deltaT=200,
dumpFreq=16000,
monitorFreq=1600000,
monitorSelect=1,
&

&PARM04
usingCartesianGrid=.TRUE.,
ygOrigin=-1050000,
delXfile='delXvar',
delYfile='delYvar',
delRfile='delZvar',
&

&PARM05
bathyFile='topog.flat',
hydrogThetaFile='Tini.bin',
uVelInitFile='Uini.bin',
vVelInitFile='Vini.bin',
pSurfInitFile='ETAini.bin',
&


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.mitgcm.org/pipermail/mitgcm-support/attachments/20171115/1fef8ea6/attachment.html>