GMI Brightness Temperatures

This directory contains the code to convert the GMI Brightness Temperatures in HDF5 format to the DART observation sequence file format.

The dataset of interest is: “GPM GMI Common Calibrated Brightness Temperatures Collocated L1C 1.5 hours 13 km V05 (GPM_1CGPMGMI) at GES DISC” not the _R set! The short name for this dataset is ‘GPM_1CGPMGMI’.

The introductory paragraph for the dataset is:

Version 5 is the current version of the data set. Version 4 is no longer available and has been superseded by Version 5. All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence angle, Sun glint angle, and the intercalibrated brightness temperature (Tc). One or more swaths are included in a product. The radiometer data are recalibrated to a common basis so that precipitation products derived from them are consistent. 1CGMI contains common calibrated brightness temperatures from the GMI passive microwave instrument flown on the GPM satellite. 1C-R GMI is a remapped version of 1CGMI which is explained at the end of this section. Swath S1 has 9 channels which are similar to TRMM TMI (10V 10H 19V 19H 23V 37V 37H 89V 89H). Swath S2 has 4 channels similar to AMSU-B (166V 166H 183+/-3V 183+/-8V). Data for both swaths is observed in the same revolution of the instrument.

The citation information for this dataset is:

Title: GPM GMI Common Calibrated Brightness Temperatures Collocated L1C 1.5 hours 13 km V05 Version: 05 Creator: Wesley Berg Publisher: Goddard Earth Sciences Data and Information Services Center (GES DISC) > Release Date: 2016-03-03T00:00:00.000Z

Linkage: https://disc.gsfc.nasa.gov/datacollection/GPM_1CGPMGMI_05.html

Instructions to download the GPM_1CGPMGMI dataset for the GMI converter

  1. Go to https://earthdata.nasa.gov

  2. Log in (or create an account if necessary)

  3. Search for GMI L1C (the “c” here is for cross-calibrated with other satellites)

  4. Scroll down past datasets to “Matching results.”

  • Follow the link to the GMI common calibrated data set: “GPM GMI Common Calibrated Brightness Temperatures Collocated L1C 1.5 hours 13 km V05 (GPM_1CGPMGMI) at GES DISC” dataset (NOT the _R set)

  1. You should now be at the https://cmr.earthdata.nasa.gov/search/concepts/C1383813813-GES_DISC.html page.

  • Select the ‘Download data’ tab

  • Select ‘Earthdata search’

  • Select the GPM link under ‘Matching datasets’

  1. You can now select ‘Granule filters’ to choose your start and end dates.

  2. Select the granules you want, then click ‘download all’ and ‘download data’

  3. Click download access script

  4. Follow the instructions on that page to download the data.

Each granule is about 28M and has names like:
1C.GPM.GMI.XCAL2016-C.20160621-S001235-E014508.013137.V05A.HDF5

Guidelines for converting the observations, thinning, superobbing, etc. are forthcoming. For more background on assimilating radiances in DART, please read https://dart.ucar.edu/pages/Radiance_support.html

When running the DART converter, two swaths (S1, S2) are converted to observations. S1 and S2 have different channels and different “postings,” meaning actual observation locations. They are more or less right next to each other …

https://disc.gsfc.nasa.gov/datasets/GPM_1CGPMGMI_05/summary

Swath S1 has 9 channels which are similar to TRMM TMI (10V 10H 19V 19H 23V 37V 37H 89V 89H).
Swath S2 has 4 channels similar to AMSU-B (166V 166H 183+/-3V 183+/-8V).
Data for both swaths is observed in the same revolution of the instrument.

Partial run-time output for one file (no thinning, whole globe, i.e. about 8 million observations):

 ...
  Data Metadata: observation
    QC Metadata: GMI QC
First timestamp: day=151747, sec=6309
  calendar Date: 2016 Jun 21 01:45:09
 Last timestamp: day=151747, sec=11863
  calendar Date: 2016 Jun 21 03:17:43
  Number of obs processed  :               5734296
  ---------------------------------------------------------
                     GPM_1_GMI_TB 5734296 obs

 add_swath_observations:  Converted      5734296  obs for swath /S1; total GMI obs =      5734296

  Data Metadata: observation
    QC Metadata: GMI QC
First timestamp: day=151747, sec=6309
  calendar Date: 2016 Jun 21 01:45:09
 Last timestamp: day=151747, sec=11863
  calendar Date: 2016 Jun 21 03:17:43
  Number of obs processed  :               8279480
  ---------------------------------------------------------
                     GPM_1_GMI_TB 8279480 obs

 add_swath_observations:  Converted      2545184  obs for swath /S2; total GMI obs =      8279480

 write_obs_seq  opening unformatted observation sequence file "obs_seq.gmi"
 write_obs_seq  closed observation sequence file "obs_seq.gmi"
 convert_gmi_L1.f90 Finished successfully.
 ...