[MITgcm-support] cube sphere 510 initial conditions

[Martin Losch]

Hi Zhaomin,

I use the initial conditions of the cs510 without any problems. Just regridding to lat/lon for plotting is not enough, you also need to change the orientation (for the physicists among us: a vector transforms differently from a scalar!, so you cannot treat u or v like theta, see also my previous email to you <http://mitgcm.org/pipermail/mitgcm-support/2011-April/007071.html>). When you read and plot them like this (matlab):

% use whatever way u use to read the inital conditions
u=rdmds('UVEL',0);
v=rdmds('VVEL',0);
j=1:510; i=j+5*510;
% surface velocities on the southern face
u=u(i,j,1);
v=v(i,j,1);
% rough averaging to c-points (does not work along the edges of the of the face):
uc = .5*(u+u([2:end 1],:));
vc = .5*(v+v([2:end 1],:));
% grid orientation (cos and sin of grid north relative to geographical north)
cs = rdmds('AngleCS');
sn = rdmds('AngleSN');
%
sh   =subplot(221); pcol(sq(uc)'); title('u grid')
sh(2)=subplot(222); pcol(sq(vc)'); title('v grid')
sh(3)=subplot(223); pcol(sq(uc.*cs(i,j)-vc.*sn(i,j))'); title('zonal velocity')
sh(4)=subplot(224); pcol(sq(uc.*sn(i,j)+vc.*cs(i,j))'); title('meridional velocitiy')
axis(sh,'image')
set(sh,'clim',[-1 1]*.5)

You'll see the difference. I am attaching my results of this, the zonal velocity is mostly positive in the ACC, but the u-grid velocitiy is not.

Martin

On Apr 6, 2011, at 10:07 AM, Wang, Zhaomin wrote:

> Dimitris,
> 
> Thanks. We have re-grided UVEL from cube sphere to spherical coordinate. So, UVEL should be eastward velocity after re-griding.
> 
> Zhaomin
> 
> -----Original Message-----
> From: Menemenlis, Dimitris (3248) [mailto:Dimitris.Menemenlis at jpl.nasa.gov] 
> Sent: 06 April 2011 01:33
> To: mitgcm-support at mitgcm.org
> Cc: Zhang, Hong (3248-Affiliate); Jean-Baptiste Sallee; Wang, Zhaomin
> Subject: Re: [MITgcm-support] cube sphere 510 initial conditions
> 
> Zhaomin, UVEL is not eastward velocity, it is referenced relative to the grid, in the case of the ACC relative to the face 6 or the Antarctic face of the cube.  Did you rotate the velocity prior to generating your figures?
> 
> 
> 
> Dimitris Menemenlis
> cell: 818-625-6498
> 
> On Apr 5, 2011, at 7:19 AM, Wang, Zhaomin wrote:
> 
>> Hi,
>> 
>> We are setting up a cube sphere 510 run at British Antarctic Survey. We downloaded initial conditions and forcing files from http://ecco2.jpl.nasa.gov/data1/cube/run_template/. We thought that the initial conditions were obtained from some spin-up runs. However, we noticed that UVEL does not look right in the ACC, say, there is a reasonable eastward transport between the Antarctic and the South Africa, but a large westward transport between the Antarctic and Australia. We would like to know where we can find proper initial conditions that are the results of a spin-up run and forcing files for cs510 case.
>> 
>> Many thanks.
>> 
>> Zhaomin
>> British Antarctic Survey
>> High Cross, Madingley Road
>> Cambridge, CB3 0ET
>> UK
>> Tel: +44(0)1223221488
>> Fax: +44(0)1223221279
> 
> -- 
> This message (and any attachments) is for the recipient only NERC
> is subject to the Freedom of Information Act 2000 and the contents
> of this email and any reply you make may be disclosed by NERC unless
> it is exempt from release under the Act. Any material supplied to
> NERC may be stored in an electronic records management system.
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
-------------- next part --------------
A non-text attachment was scrubbed...
Name: rotatedvel.png
Type: image/png
Size: 124170 bytes
Desc: not available
URL: <http://mitgcm.org/pipermail/mitgcm-support/attachments/20110406/529643c2/attachment-0001.png>