NetCDF Format for SRF Data

[Aleksandar Jelenak - NOAA Affiliate]

Dear all:

Right after our annual meeting earlier this month I was asked to produce netCDF files with spectral response data (SRF) for several GEO imager instruments in preparation for the future DCC inter-calibration activities. I have produced a prototype file and the ncdump of its content is below. New features not appearing in our netCDF files so far are in the bold font.

netcdf goes13-imager-srf {

dimensions:

chan = 5 ;

chan_strlen = 3 ;

wlen = 13313 ;

variables:

char channel(chan, chan_strlen) ;

channel:long_name = "channel identifier" ;

double wavelength(wlen, chan) ;

wavelength:_FillValue = -9999. ;

wavelength:valid_min = 3.e-07 ;

wavelength:coordinates = "channel" ;

wavelength:long_name = "wavelength" ;

wavelength:standard_name = "radiation_wavelength" ;

wavelength:units = "um" ;

wavelength:valid_max = 15. ;

double srf(wlen, chan) ;

srf:_FillValue = -9999. ;

srf:units = "1" ;

srf:long_name = "spectral response function" ;

srf:valid_min = -1.e-06 ;

srf:valid_max = 1. ;

srf:coordinates = "channel" ;

// global attributes:

:Conventions = "CF-1.6" ;

:Metadata_Conventions = "Unidata Dataset Discovery v1.0" ;

:standard_name_vocabulary = "CF Standard Name Table (v22, 12 February 2013)" ;

:project = "Global Space-based Inter-Calibration System <http://gsics.wmo.int>" ;

:title = "GOES-13 Imager Channel Spectral Response Data" ;

:summary = "Spectral response functions (SRF) for all channels of the GOES-13 Imager instrument are stored in this file. The data came from the official text files (see the source global attribute). The only difference is that SRF data given in wavenumbers are converted to wavelengths." ;

:naming_authority = "gov.noaa.nesdis.gsics" ;

:id = "goes13-imager-srf.nc" ;

:institution = "NOAA/NESDIS Center for Satellite Applications and Research" ;

:creator_name = "NOAA/NESDIS Center for Satellite Applications and Research GPRC" ;

:creator_email = "nesdis.s...@noaa.gov" ;

:creator_url = "https://gsics.nesdis.noaa.gov/wiki/GPRC" ;

:contributor_name = "Fangfang Yu <Fangf...@noaa.gov>" ;

:contributor_role = "Source of original SRF data text files" ;

:date_created = "2013-03-29T00:33:45Z" ;

:history = "2013-03-29T00:33:45Z srf2nc.py v1.0.0" ;

:source = "g13_img_vis_det6.txt (MD5=1be63b3c6695f592d755d1252bedf46c); g13_img_srf_v3_038.txt (MD5=8c4ef210d0a5442acc6237f753bf13bf); g13_img_srf_v3_065.txt (MD5=6003ba3ec35d3f2dabf91f74b10263cc); g13_img_srf_v3_107.txt (MD5=954eef23082f2904ffc427c04174526a); g13_img_srf_v3_133.txt (MD5=64f5a61f4171b136e3ed5c1cc88e59c9)" ;

:platform = "GOES-13" ;

:instrument = "Imager" ;

:wmo_satellite_id = 257 ;

:wmo_instrument_id = 615 ;

}

Highlighted features:

1. No "license" attribute. These files can be considered GSICS intermediate data for which we did not develop a suitable license text.
2. "contributor_name|role" attributes to document the provider of the original SRF data.
3. "source" attribute to document the original files from which SRF data came from. Each file's MD5 checksum is also recorded to allow comparison with possible future versions of same files.
4. "platform" and "instrument" attributes to specify the instrument for which the SRF data applies.
5. "wmo_satellite_id" and "wmo_instrument_id" with satellite and instrument identifiers from the WMO Common Code Tables C5 and C8. I plan to include these whenever available.
6. I would like to use the netCDF-4 format for these files. No real need in this case beside my wish that we start migrating to this format for all our data sets and could use these files for testing.

Let me know if you have any suggestions on the content and its organization. I would like to release these files before the DCC web meeting on May 29.

       -Aleksandar

[Aleksandar Jelenak - NOAA Affiliate]

Dear All:

The SRF data for some of the GEO imager instruments from NOAA,
EUMETSAT, JMA, and KMA are now available from the NOAA GSICS data
server:

http://gsics.nesdis.noaa.gov/thredds/instrument-srf.html

-Aleksandar

[Aleksandar Jelenak - NOAA Affiliate]

Dear GSICS colleagues:

I have decided to update the SRF files after receiving some comments
and a user request to add data for the GOES-11 and -12 Imager, and the
MTSAT-1R JAMI. The files are available from:

http://gsics.nesdis.noaa.gov/thredds/instrument-srf.html

One of the most discussed issues when initially planning these files
was what to do with SRF data given in the wavenumber domain. This
discussion is irrelevant now because the new version of the files has
two new variables. One variable contains the wavenumber values of SRF
sample points for all channels:

double wavenumber(sample, channel) ;
:long_name = "wavenumber" ;
:units = "cm-1" ;
:_FillValue = -9999. ;
:comment = "Values are in descending order." ;
:ancillary_variables = "origin" ;
:valid_min = 666.666666666667 ;
:valid_max = 33333.3333333333 ;

while the other variable holds flag values that point to the original
spectral domain for each channel's data:

ubyte origin(channel) ;
:long_name = "original sample domain" ;
:valid_min = 1UB ;
:valid_max = 2UB ;
:flag_values = 1UB, 2UB ;
:flag_meanings = "wavelength wavenumber" ;

Users of these files now have a choice of either using SRF data in the
wavelength or the wavenumber domain, and to know in which of these
domains the original SRF data came from.

The other noticeable change is the renaming of the SRF data variable:
from "rsrf" to "srf". Simpler is better.

-Aleksandar