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20011022: 20011019: gempak ltg gridding

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
>> >
>> 
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>