# [MITgcm-support] how to initialize a 2D geostrophic flow

q li qliuri at yahoo.com
Sat May 16 20:23:23 EDT 2009

```Hi Jody and Matt,

I am sorry for the late to show you the result. There was a computer problem. I am running it now.

Here it the first run: use geopotential to get meridional velocity (v) but with zero initial Eta. Figure are in http://www.po.gso.uri.edu/~qli/picST0.zip (~4.5Mb).

Here is the configuration:

2D in a x-z domain
Vertical: 10m*300 grids
Horizontal: dx changes from 5km to 6km in the farfield, 512 grids. ~2400 km total.
The temperature is from Levitus data, and the salinity is constant.
Flat bottom.
Velocity v is calculated from the geopotential method. A jet is in the center.
dt=15 s. Output is every 3 hours. 5 day run.
Latitude: 21

There is an oscillation. The estimated period is ~33 hr, "exactly" equal to the inertial period at 21N. I am not sure if it is caused by that I didn't set up initial surface elevation Eta.

I am trying to set up the initial Eta to see any different or improvement.

Another question is that, if I have a topography featuer, for example, a sill in the center, how I should get the geotrophic flow from geopotential or thermal wind. The more basic question is how I should set up the reference level (v=0).

Li

________________________________
From: Matthew Mazloff <mmazloff at mit.edu>
To: mitgcm-support at mitgcm.org
Sent: Saturday, April 25, 2009 3:30:43 PM
Subject: Re: [MITgcm-support] how to initialize a 2D geostrophic flow

Hi Jody,

is this true -- I thought eta is solved for in first time step to make flow non-divergent?  I need to check this?

-Matt

On Apr 24, 2009, at 10:57 AM, Klymak Jody wrote:

Make sure that you set the sea surface eta properly too or you'll have some pretty nasty adjustment.  I think it is "pSurfInitFile".

Cheers,  Jody

--
Jody Klymak
http://web.uvic.ca/~jklymak/

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