[GEMPAK #BYC-706082]: Equilibrium Level Pressure

Hi Kelton,

There is no easy way to request equilibrium level from gridded model files.  
SNPROF, of course, will report EQLV, and there is a call within NSHARP which 
calculates eq. level (in $GEMPAK/source/programs/gui/nsharp/skparams.c):

/* ----- EL Possibility ----- */
if(( lyre <= 0 ) && ( lyrlast > 0 ))
{
tp3 = tp1;
te3 = te1;
pe2 = pe1;
pe3 = pelast;
while ( i_vtmp( pe3 ) < virtemp( pe3, wetlift(pe2, tp3, pe3), wetlift(pe2, tp3, 
pe3)) ) { pe3 -= 5; }
pcl->elpres = pe3;
pcl->mplpres = -999;
pcl->limax = -li_max;
pcl->limaxpres = li_maxpres;
}

But that's about it.  I tried to find a way to pull vertical levels and 
parameters from a grid file to create a sounding file but, alas, it's not 
possible in GEMPAK.  Sorry to not have any better news for you.

Lastly, there's one suggestion I can make, though it's a bit of a kludge:

NSHARP > "Show Text" > "Save" will output the vertical profile from a grid into 
a text file "DECDDROB", which then could be manually reformatted into an SN 
edit file for use in SNEDIT:

http://www.unidata.ucar.edu/cgi-bin/gempak/manual/programs_index?snedit

Not a pretty solution, and would required a number of edits to match the 
expected input for SNEFIL, but it's the only solution I see right now.

Michael James
Unidata

 


> Gempak Support,
> 
> I am wondering what the likelihood is of having GEMPAK be able to
> compute Equilibrium Level based on any type of model data (nam, ruc,
> gfs, etc). I have asked some people more educated than me in this area
> and looked through the support emails, but so far I have not found an
> answer. My understanding is that there is no clear cut way to calculate
> the EL without a sounding, but I also know that CAPE (which is computed
> by GEMPAK) cannot be computed without the EL. Is there a way to get this
> value in millibars? Or, is it possible to export this from a listing
> program or NSHARP?
> 
> My goal is to be able to calculate effective parameters - mainly involving
> wind.
> 
> Any help in this area would be greatly appreciated!
> 
> Kelton Halbert.
> 
> 


Ticket Details
===================
Ticket ID: BYC-706082
Department: Support GEMPAK
Priority: Normal
Status: Open