[ecco-support] A question related to WIND data of ecco v4 (??)

[Diana Lees Spiegel]

Hello Hao,

Your question raises two issues. Xinfeng has answered your concern about
the discontinuity by referring you to calc_UEVNfromUXVY.m.  But I'd like to
underscore another issue.

In general, for the best accuracy, it is recommended that you perform your
calculations on the ECCO V4 original grid.  Spatial interpolation on the
model grid can introduce inaccuracies in calculations, especially outside
of the region where the model uses a rectangular latlon grid (i.e. for
j=[62:239] within the array format, which corresponds to
Y=[-69.4712:56.2021])  Avoiding interpolation is particularly crucial if
you plan to calculate transports.

To calculate on the original model grid you have two choices. After loading
both oceTAUX and oceTAUY you could use convert2array on each, calculate the
time means using the array formats of oceTAUX and oceTAUY, and then again
use convert2array to convert each back to gcmfaces format.  Or you could
simply calculate time means directly in the gcmfaces format for both
oceTAUX and oceTAUY. In either case you would then use calc_UEVNfromUXVY.m
to calculate oceTAUXE and oceTAUYN from oceTAUX and oceTAUY.  oceTAUXE
would be identical in either case and plots without displaying a
discontinuity.

For a quick and dirty plot (as in qwckplot.m) you can plot an array field
in array coordinates using pcolor or imagesc. To plot in geographic
coordinates see the gcmfaces routine plot_one_field.m for examples of
convert2pcol.m and other plotting methods. Interpolating the array field to
a regular grid and plotting with your favorite Matlab 2D plotting routine
may produce results similar to convert2pcol, but I'm not certain the polar
cap will be correct.

Hope this is clear,
Diana Spiegel


======================================================================
Diana Spiegel                           office:       54-1412
Oceanography (EAPS Dept)                phone:        617-253-2092
Massachusetts Institute of Technology
======================================================================


On Wed, Sep 23, 2015 at 3:57 PM, Xinfeng Liang <xliang at mit.edu> wrote:

> Hi Hao,
>
> As shown in Figure 3 in the gcmfaces manual (
> http://mitgcm.org/viewvc/*checkout*/MITgcm/MITgcm_contrib/gael/matlab_class/gcmfaces.pdf),
> the whole domain includes five different faces, three of which need to be
> rotated to get the zonal and meridional components of vectors. If I
> remember correctly, this can be done using calc_UEVNfromUXVY.m (included in
> the gcmfaces package). Please let us know whether that works for you.
>
> Cheers,
> Xinfeng
>
> > On Sep 23, 2015, at 3:34 PM, ecco-support-request at MIT.EDU wrote:
> >
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> >   1. A question related to WIND data of ecco v4 (??)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Wed, 23 Sep 2015 11:20:34 -0400
> > From: ?? <hliu at whoi.edu>
> > Subject: [ecco-support] A question related to WIND data of ecco v4
> > To: ecco-support at mit.edu
> > Message-ID: <5602C342.4080702 at whoi.edu>
> > Content-Type: text/plain; charset="utf-8"
> >
> > Hi,
> >             I mapped a gridded zonal wind stress data  ,and find a
> > discontinuity around 150E and 40W,attachment is what I did.
> >           Why is there a discontinuity?
> >           How I do it: First  I use gcmfaces to load oceTAUX ,then I
> > use convert2array code to transfer to array data ,then I griddata them
> > in matlab ,and at last mean the whole period.
> >          Looking forward to hearing from you!
> > Sincerely,Hao
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