[MITgcm-support] question about Cartesian Grid in Matlab

[yang.zhang]

Hello, Colleagues
I have a Tutorial_barotropic_gyre result here to show question (I am quite
new in MITgcm);
The wind force is from the west to the east with a Sine  variation in
south-north direction;
I draw the wind force in 'Barotropic Gyre1 tif' in the attachment.

So the wind-driven flow is like 'Barotropic Gyre2 tif' in the attachment.
The contour is Eta(sea surface height);
They both seems good; But the vertical velocity W in 'Barotropic Gyre3 tif'
confused me a lot, Because a anti-clockwise gyre in the north should has a
UPwelling effect (Positive W); and It should be a Downwelling (Negative W)
in south because of the clockwise gyre in the south. But 'Barotropic
Gyre3.tif' gives opposite.

if Xc, Yc are the grid file for U V output:
These pictures in the attachment is drawn in Matlab like this:
contour（Xc,Yc,Eta）;
hold on;
quiver(Xc,Yc,U,V)

Barotropic Gyre4 tif is made by this:
contour(Eta);
hold on;
quiver(U,V);
It gives a reasonable result: the divergence results in Positive W; while
the convergence gives Negative W.

I don't know which kind of plot is right? or they are both right?
Any reply will be appreciated!

Yang
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