<div class="gmail_quote">On Sun, May 25, 2008 at 7:18 AM, Luis Aimola <<a href="mailto:luis.aimola@weizmann.ac.il">luis.aimola@weizmann.ac.il</a>> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;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@alum.mit.edu">dasilva@alum.mit.edu</a>