No subject
Wed Apr 14 09:37:02 EDT 2010
To GRADSUSR at LIST.CINECA.IT
Subject Re: Vertical wind field from horizontal ones
On Sun, May 25, 2008 at 7:18 AM, Luis Aimola <luis.aimola at weizmann.ac.il (m=
ailto:luis.aimola at weizmann.ac.il)> wrote:
Hi GRADS colleagues:
I have horizontal wind fields for several presure levels. Has GRADS some sc=
ript to construct from these fields a vertical wind profile to look for exa=
mple 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 poten=
tial which would help you to identify the ascending and descending branches=
of the Walker circulation. You can infer vertical velocity from wind diver=
gence, but this is generally a noisy quantity. If your fields are global, y=
ou can compute velocity potential with the "fish" extension available with =
v1.9.0-rc1:
=A0=A0 http://opengrads.org/doc/udxt/fish/ (http://opengrads.org/doc/udxt/f=
ish/)
To find out more about the OpenGrADS extensions, including download and ins=
tallation, see here:
=A0=A0 =A0http://opengrads.org/wiki/index.php?title=3DUser_Defined_Extensio=
ns (http://opengrads.org/wiki/index.php?title=3DUser_Defined_Extensions)
For older versions of GrADS, Mike Fiorino had a classic psi/chi UDF.=A0
=A0=A0 =A0Arlindo
--
Arlindo da Silva
dasilva at alum.mit.edu (mailto:dasilva at alum.mit.edu)
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<HTML><head></head><body><div><font style="color: rgb(0, 0, 0);" face="tahoma,verdana,sans-serif" size="2">Thank you Arlindo.<br>
<br>
The best.<br>
<br>
Luis<br>
<br>
</font></div><div><font color="#000000" face="tahoma,verdana,sans-serif" size="2"><br><br></font><hr><div><span style="font-weight: bold;">From </span><span>Arlindo da Silva <dasilva at ALUM.MIT.EDU></span></div><div><span style="font-weight: bold;">Sent </span><span>Mon 5/26/2008 1:07 AM</span></div><div><span style="font-weight: bold;">To </span><span>GRADSUSR at LIST.CINECA.IT</span></div><div><span style="font-weight: bold;">Subject </span><span>Re: Vertical wind field from horizontal ones</span></div><br></div><div class="gmail_quote">On Sun, May 25, 2008 at 7:18 AM, Luis Aimola <<a href="mailto:luis.aimola at weizmann.ac.il">luis.aimola at weizmann.ac.il</a>> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div style="font-family: tahoma,verdana,sans-serif; font-size: 100%; color: rgb(0, 0, 0);"><font style="color: rgb(0, 0, 0);" face="tahoma,verdana,sans-serif" size="2">Hi GRADS colleagues:<br>
<br>
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?<br>
Thank you if someone can help me.</font></div></div></blockquote><div><br></div><div>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:</div>
<div><br></div><div> <a href="http://opengrads.org/doc/udxt/fish/">http://opengrads.org/doc/udxt/fish/</a><br></div><div><br></div><div>To find out more about the OpenGrADS extensions, including download and installation, see here:</div>
<div><br></div><div> <a href="http://opengrads.org/wiki/index.php?title=User_Defined_Extensions">http://opengrads.org/wiki/index.php?title=User_Defined_Extensions</a><br></div><div><br></div><div>For older versions of GrADS, Mike Fiorino had a classic psi/chi UDF. </div>
<div><br></div><div> Arlindo</div><div><br></div></div>-- <br>Arlindo da Silva<br><a href="mailto:dasilva at alum.mit.edu">dasilva at alum.mit.edu</a>
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