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[GEMPAK #QHI-262030]: GOES-17, gpmap color tables

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  • Subject: [GEMPAK #QHI-262030]: GOES-17, gpmap color tables
  • Date: Thu, 05 Sep 2019 13:13:43 -0600
Hi Luis,

re:
> I am using a set of netcdf files from GOES-17 to make a display of products
> from channel 13. These files are from
> 
> https://atm.ucar.edu/native/satellite/GOES/GRB17/Products/CloudAndMoistureImagery/Mesoscale-2/Channel13
> 
> and the gpmap program from GEMPAK version 7.5.1. For the above infrared 
> channel
> (10.7?m) files, I am using lookup tables (LUTFIL) that worked well on the
> previous GOES satellites (ir_upc.tbl and ir_upc2.tbl).

OK.

re:
> However, for GOES-17, I am not able to identify a table that resembles what
> one was able to do with GOES-13 and GOES-15.

I tip that was provided by one of the GEMPAK experts in the community is
that there is a need to modify the entry in imgtyp.tbl:

 "There is a table that sets the min/max pixel values for
  an image. The table is $GEMPAK/tables/sat/imgtyp.tbl. The
  max values for GOES16 and GOES17 non-visible imagery need
  to be adjusted. I tested with a Channel 4 image and had
  to set the max value to 128. I did this because the NetCDF
  file says that the data range is 0-4095. However to map to
  the color tables, the data is scaled to 0-255 by shifting
  to the right 4 bits. This should work, but I found that the
  data range for the image I tested is actually 0-2082. When
  this range is shifted 4 bits, the range becomes 0-(about)130.
  Modifying imgtyp.tbl with the new max value makes the colors
  look correct."

> These are examples of my displays for tropical cyclone Juliette in
> the eastern Pacific Ocean:
> 
> https://met-bcs.cicese.mx/satelite/GOES17_channel13_new01.gif (LUTFIL= 
> ir_upc.tbl)
> https://met-bcs.cicese.mx/satelite/GOES17_channel13_new02.gif (LUTFIL= 
> ir_upc2.tbl)
> 
> Are you able to provide guidance to improve my images with respect to the
> available color tables?

Please try implementing the change to imgtyp.tbl as recommended above.


Cheers,

Tom
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Ticket Details
===================
Ticket ID: QHI-262030
Department: Support GEMPAK
Priority: Normal
Status: Closed
===================
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