20011023: 20011022: 20011019: gempak ltg gridding

Brian,

I have created a program called GDOBSCNT that will find the
number of observations within a specified radius of each grid
point and store the grid as parameter ODEN@0%none for each 
time specified from the input surface file.

You can download the tarfile from:
http://www.unidata.ucar.edu/packages/gempak/contrib/gdobscnt.tar.Z

In your GEMPAK 5.6 $NAWIPS directory, unpack the tarfile with:

zcat gdobscnt.tar.Z | tar xvf -

Then build and install with:

cd $NAWIPS/unidata/programs/gdobscnt
make clean
make all
make install
make clean


To use the program, you should first create your grid file with your 
required grid spacing using GDCFIL. 

The program uses 4 parameters. SFFILE, DATTIM, GDFILE, RADIUS.
SFFILE is your input surface (NLDN) file. GDFILE is the
file for the grids to be stored. DATTIM is the times
(a list, range, single, or all) from the surface file
to process. RADIUS is the range, in meters, from the
each grid point that stations will be counted.

The result is a grid called ODEN for each time specified
by DATTIM.

For example, using today's 1630Z NLDN file (which contains
nldn bins at 5 minute intervals from 1630Z to 1655Z), and a grid 
file I have already created called test.grd specifying a 50KM
radius (50000m):

% gdobscnt
 SFFILE    Surface data file                 nldn|011024/1630
 DATTIM    Date/time                         all
 GDFILE    Grid file                         test.grd
 RADIUS    Radius (in meters) to search      50000
 Parameters requested: SFFILE,DATTIM,GDFILE,RADIUS.
 GEMPAK-GDOBSCNT>r
 Processing 011024/1630    
 Processing 011024/1635    
 Processing 011024/1640    
 Processing 011024/1645    
 Processing 011024/1650    
 Processing 011024/1655    
 Parameters requested: SFFILE,DATTIM,GDFILE,RADIUS.
 GEMPAK-GDOBSCNT>e

I can then plot the data, with grid point values and contous in GDPLOT2
with:
 GDFILE   = test.grd
 GDATTIM  = 1630-1655
 GLEVEL   = 0
 GVCORD   = none
 PANEL    = 0
 SKIP     = 0
 SCALE    = 0
 GDPFUN   = ODEN
 TYPE     = cm
 CONTUR   = 0
 CINT     = 0
 LINE     = 3
 FINT     = 
 FLINE    = 
 HILO     =  
 HLSYM    =  
 CLRBAR   = 1
 WIND     = 
 REFVEC   =  
 TITLE    = 1
 TEXT     = 1
 CLEAR    = y
 GAREA    = 34.0;-95.2;43.7;-79.2
 PROJ     = LCC/25.0;-90.0;25.0
 MAP      = 1
 LATLON   = 0
 DEVICE   = XW
 STNPLT   =  
 SATFIL   =  
 RADFIL   =  
 LUTFIL   =  
 STREAM   =  
 POSN     = 0
 COLORS   = 5
 MARKER   = 0
 GRDLBL   = 0
 FILTER   = 0
 GEMPAK-GDPLOT2>r
Creating process: xw for queue 12551
 [TG 0] 1630-1655
 Number of times =            6
            1 011024/1630
            2 011024/1635
            3 011024/1640
            4 011024/1645
            5 011024/1650
            6 011024/1655
<etc...>

The TYPE=cm in gdplot2 will plot both the contours of the data as well as
the data values at the grid point locations (marker=0).

Let me know if you have questions/problems/etc.

Steve Chiswell
Unidata User Support










>From: Unidata Support <address@hidden>
>Organization: UCAR/Unidata

>
>Brian,
>
>The ltgmap program was the same program as sfmap. It just allowed a 
>greater number of times/observations. In GEMPAK 5.6, I increased
>the number of times/observations in sfmap so that a separate ltgmap program
>wasn't needed.
>
>The lat/lon locations are the station locations (each lightning strike
>is treated as a "ship" report).
>
>I can create a program in the next few days that will read the surface file 
>and create the grid of "reports within a DELTA radius".
>
>Steve Chiswell
>Unidata User SUpport
>
>
>
>
>
>>From: Brian Colle <address@hidden>
>>Organization: UCAR/Unidata
>>Keywords: 200110222134.f9MLY8102451
>
>>
>>Steve,
>>
>>> 
>>> Brian,
>>> 
>>> At this point in time, there is nothing within GEMPAK
>>> to make this type of computation as you require.
>>> 
>>> I would be possible to write a program to accumulate the number
>>> of strikes within a given radius of a grid point.
>>>
>>
>>In order to write another program I need to know how to open and
>>read the ltg sfc file to extract the lat/longs for each lightning strike,
>>assuming that they are stored that way. Just to clarify, is there a gempak
>>fortran subroutine that will read the file and extract this information?
>>For example, I used to use ltgmap, which plotted the individual lightning
>>strikes. I was hoping that I could take advantage of the way ltgmap reads
>>in the data, but only use the lat/long info. I notice that the latest
>>version of gempak doesn't even use ltgmap anymore?
>> 
>>> The other limitation you would have is that a 3km grid is going
>>> to be a very large grid if you are attempting to cover the
>>> entire country with a single grid. At present time, the default
>>> maximum number of grid points in a file is 400,000.
>>> A 4km national grid is approximately 1,200,000 points.
>>> 
>>> If you are doing a regional (or series of regional) grids
>>> then that won't be a problem.
>>> 
>>
>>Yes, I only want the regional NE US.
>>
>>Thanks again,
>>
>>Brian
>>
>>> >
>>> >Hi,
>>> >
>>> >I have some gempak lightning data (surface files of sgnl strength) that I
>>> >want to interpolate to a uniformly spaced 3-km gempak grid such that each
>>> >grid point has the number of nearby strikes. With this gridded file I can
>>> >then contour the number density up in gempak. 
>>> >
>>> >Do you have any ideas or sample code how I can do this interpolation 
>>> >of lightning data within gempak or interfacing gempak with f77? 
>>> >
>>> >I appologize in advance for the loaded question, but I am looking
>>> >for ideas at this point.
>>> >
>>> >Thanks for your time...
>>> >
>>> >Brian
>>> >____________________________________________________________
>>> >Prof. Brian Colle         INTERNET: address@hidden
>>> >(631)632-3174
>>> >Institute for Terrestrial and Planetary Atmospheres
>>> >Marine Sciences Research Center
>>> >State University of New York at Stony Brook
>>> >Stony Brook, NY 11794-5000
>>> >
>>> 
>>> ***************************************************************************
> *
>>> Unidata User Support                                    UCAR Unidata Progra
> m
>>> (303)497-8644                                                  P.O. Box 300
> 0
>>> address@hidden                                   Boulder, CO 8030
> 7
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>>> Unidata WWW Service                        http://www.unidata.ucar.edu/    
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>>> 
>>
>
>