Vertical wind field from horizontal ones

[Arlindo da Silva]

On Sun, May 25, 2008 at 7:18 AM, Luis Aimola <luis.aimola at weizmann.ac.il>
wrote:

> Hi GRADS colleagues:
>
> I have horizontal wind fields for several presure levels. Has GRADS some
> script to construct from these fields a vertical wind profile to look for
> example the Walker circulation on the Equator?
> Thank you if someone can help me.
>

Having the horizontal winds, your best bet is to compute the velocity
potential which would help you to identify the ascending and descending
branches of the Walker circulation. You can infer vertical velocity from
wind divergence, but this is generally a noisy quantity. If your fields are
global, you can compute velocity potential with the "fish" extension
available with v1.9.0-rc1:

   http://opengrads.org/doc/udxt/fish/

To find out more about the OpenGrADS extensions, including download and
installation, see here:

    http://opengrads.org/wiki/index.php?title=User_Defined_Extensions

For older versions of GrADS, Mike Fiorino had a classic psi/chi UDF.

    Arlindo

--
Arlindo da Silva
dasilva at alum.mit.edu
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