[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[GEMPAK #RTU-170761]: GEMPAK - sigma coordinates for gdcross

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: [GEMPAK #RTU-170761]: GEMPAK - sigma coordinates for gdcross
  • Date: Tue, 26 Jun 2007 16:03:26 -0600
> Institution: North Carolina State University
> Package Version: 5.10
> Operating System: Linux
> Hardware Information: n/a
> Inquiry: I noticed a previous thread about elvl coordinates from wrf output 
> stating that GEMPAK will only recognize the vertical coordinate 'sgma'.  Is 
> there a fundamental difference between what GEMPAK recognizes as 'sgma' and 
> the wrf 'elvl' converted output?  More to the point, would it be possible to 
> simply rename the GVCORD of each variable to 'sgma'?
> 
> Thanks in advance,
> Barrett
> 
> 
> 
> 

Barrett,

You can use any 4 letter vertical coordinate name in GEMPAK. The only ones that
GEMPAK knows about for coordinate transformation purposes are NONE, PRES, THTA, 
SGMA, HGHT.
You can plot your data on ELVL in GEMPAK with no problem, so you don't have to 
convert it. 
However, certain programs, such as GDVINT, require some knowledge about 
vertical coordinates 
in order to interpolate levels, and GDCROSS to display the Yaxis direction. The 
definition
of eta value on half (mass) levels is not synonymous with SGMA.

I found the following from Kelley Mahoney in your department:
http://wikis.lib.ncsu.edu/index.php/Forecasting_Lab_Guide_to_using_the_WRF_Model_at_NC_State
The conversion was for the sake of plotting convention, but does not imply the
same value of SGMA for the purpose of coordinate transformations.

Steve Chiswell
Unidata User Support



Ticket Details
===================
Ticket ID: RTU-170761
Department: Support GEMPAK
Priority: Urgent
Status: Closed