19990716: gempak/garp <fwd>

John,

I looked at the DV_PVOR code I mentioned the other day, and
verified that the PVOR formula includes the -g term.

As you mention below, the PVOR equation can accept either
THTA/THTE/STHA when the layer is pressure and tmperature when
operating in isentropic coordinates.

I plotted a cross section of today's eta using PVOR(THTA,WND)
and the PV values are on the order of 1.2 to 1.6 around 300 mb and
increasing rapidly above this. 

Steve Chiswell
Unidata User Support



On Thu, 15 Jul 1999, John Knox wrote:

> Dear Steve,
> 
> Here's the problem. {See e-mail appended below.}  I 
> cross-verified this fix by using someone else's code who 
> also used thta, not tmpk, and it works.  I should have 
> checked the variable definition more carefully... I saw 
> "TMPK" and because theta (potential temperature) is always 
> in degrees K, it didn't occur to me that that wasn't 
> potential temperature.  This would completely explain the 
> not-quite-order-of-magnitude differences.
> 
> John
> 
> 
> --- Begin Forwarded Message ---
> Date: Thu, 15 Jul 1999 14:31:10 -0700 (PDT)
> From: Lynn McMurdie <address@hidden>
> Subject: gempak/garp
> Sender: Lynn McMurdie <address@hidden>
> To: address@hidden
> 
> Reply-To: Lynn McMurdie <address@hidden>
> Message-ID: 
> <address@hidden>
> 
> 
> Hi John...
> 
> In the cross-section part of garp, select PotVort_Ks-1P-1 and change
> the line below FROM:
> 
> PVOR (TMPK,WND)
> 
> to PVOR (THTA,WND).
> 
> Potential vorticity should be in terms of theta.  You could still
> divide by gravity, but maybe it shouldn't be negative gravity.  Don't
> have the time to ponder the units at this moment, but give that a try
> and see if the magnitudes look better.
> 
> Good luck....garp is SO MUCH fun!!!
> 
> Cheers,
>       Lynn
> -- 
> Lynn McMurdie         INTERNET: address@hidden
> (206) 685-9405                UUCP:     
> uw-beaver!atmos.washington.edu!mcmurdie
> Dept of Atmospheric Sciences
> University of Washington
> Box 351640
> Seattle, WA  98195
> --- End Forwarded Message ---
> 
> 
> ------------------------------------------------
> Dr. John A. Knox
> Assistant Professor of Geography and Meteorology
> Room 15, Mueller Hall
> Valparaiso University
> Valparaiso, IN 46383
> E-mail: address@hidden
> Office Phone: 219-464-6003
> 
>