Hi,<br><br>Follow up on WRF vertical levels. Yes, WRF uses model levels. I used ARW post to convert my model levels to pressure and height levels. So, now I have geopotential and other parameters with height and pressure levels. I was trying to plot them in grads because ARW post gives the output in .ctl and .dat format. <br>
<br>I followed the suggestion 0.5*(geopt(z+1)-geopt(z-1)) and it worked out. Although I'm not sure of my answer. <br><br>Thank you all,<br>Aishwarya.<br><br><div class="gmail_quote">On Tue, May 8, 2012 at 4:10 PM, Eric Altshuler <span dir="ltr"><<a href="mailto:ela@cola.iges.org" target="_blank">ela@cola.iges.org</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">As I recall, the person who started this thread is using WRF. The vertical coordinate in raw WRF history output is neither pressure nor height, but a hybrid coordinate. In grads, z levels would correspond to constant hybrid coordinate surfaces. Taking vertical derivatives with respect to this hybrid coordinate would not be very useful. The available postprocessing tools for WRF can interpolate fields onto pressure or height levels.<br>
<span class="HOEnZb"><font color="#888888"><br>
Eric<br>
</font></span><div class="HOEnZb"><div class="h5"><br>
----- Original Message -----<br>
From: "Arlindo da Silva" <<a href="mailto:dasilva@alum.mit.edu">dasilva@alum.mit.edu</a>><br>
To: "GrADS Users Forum" <<a href="mailto:gradsusr@gradsusr.org">gradsusr@gradsusr.org</a>><br>
Sent: Tuesday, May 8, 2012 2:21:41 PM<br>
Subject: Re: [gradsusr] Grads vertical derivative error with cdiff<br>
<br>
<br>
On Tue, May 8, 2012 at 1:42 PM, Andre Pattantyus < <a href="mailto:apattantyus2008@my.fit.edu">apattantyus2008@my.fit.edu</a> > wrote:<br>
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<br>
<br>
you need to use geopotential on pressure surface you will never get an answer with z coordinate. This is a basic units concept people!<br>
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In GrADS "z" is used to refer to the vertical dimension in index space, whatever that is: pressure or height.<br>
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Arlindo<br>
--<br>
Arlindo da Silva<br>
<a href="mailto:dasilva@alum.mit.edu">dasilva@alum.mit.edu</a><br>
<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br><font style="font-family:times new roman,serif" size="2"><i><span style="color:rgb(153,0,0)">Aishwarya,</span><br style="color:rgb(153,0,0)"><span style="color:rgb(153,0,0)">Graduate Research Assistant,</span><br style="color:rgb(153,0,0)">
<span style="color:rgb(153,0,0)">Atmospheric Sciences,</span><br style="color:rgb(153,0,0)"><span style="color:rgb(153,0,0)">University of Arizona,Tucson.</span></i></font><br><br>