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NCEP/CPC L3 Half Hourly 4km Global (60S - 60N) Merged IR V1 (GPM_MERGIR) at GES DISC

Metadata Updated: December 6, 2023

These data originate from NOAA/NCEP.

The NOAA Climate Prediction Center/NCEP/NWS is making the data available originally in binary format, in a weekly rotating archive. The NASA GES DISC is acquiring the binary files as they become available, converts them into CF (Climate and Forecast) -convention compliant netCDF-4 format, and stores the product in a permanent archive. It has been the intention to extend the record back to TRMM epoch, and some data are available from 1998. However, currently, the continuous record starts from February, 2000.

The leading edge of data availability is delayed by about 24 hours from real-time to abide by international data exchange agreements between NOAA and EUMETSAT (the METEOSAT data providers).

The data contain globally-merged (60S-60N) 4-km pixel-resolution IR brightness temperature data (equivalent blackbody temps), merged from the European, Japanese, and U.S. geostationary satellites over the period of record (GOES-8/9/10/11/12/13/14/15/16, METEOSAT-5/7/8/9/10, and GMS-5/MTSat-1R/2/Himawari-8).

The data have been corrected for "zenith angle dependence", i.e. IR temperatures for locations far from satellite nadir are erroneously cold due to a combination of geometric effects and radiometric path extinction effects. This correction allows for the merging of the IR data from the various geostationary satellites with greatly reduced discontinuities at their boundaries. Some residual differences among the data exist since the IR channels aboard the various spacecraft have slightly different characteristics and no intercalibration among the sensors has been performed. NOAA are in the process of performing such an intercalibration, although this effect is considerably smaller than the zenith angle effects.

The NASA GES DISC is curating these data in a self-documenting, CF-compliant, netCDF-4 format, which allows a broad range of applications to access the data directly, without the need to cope with the original binary data format. In addition to the direct download of netCDF-4 data, the GES DISC provides data download in binary, ASCII, and netCDF-3 formats using the OPeNDAP interface.

Similarities with the original

As in the original binaries, every netCDF-4 file covers one hour, and contains two half-hourly grids, at 4-km grid cell resolution.

Differences from the original

  1. The data in the netCDF-4 files are already converted to real (float) values of Brightness Temperatures in Kelvin. There is no need to further scale these data. The netCDF-4 format is machine-independent and users need not worry about the endian-ness of their machines.

  2. To meet the requirements of collection spatial metadata, the grid is re-ordered from the original and now goes from -180 (West) to 180 (East). It is also starting from -60 (South).

The data and time units are reflected in the corresponding "units" attributes, and grid dimensions are described by longitude ("lon"), latitude ("lat") and "time" vectors. Thus, any CF-compliant tool should automatically understand the setup in the data files and the starting time for each half-hourly grid. Even without such tools, simple "ncdump" or "h5dump" command line tools will easily disclose the netCDF-4 files configuration.


The creation of the original data at NOAA/NCEP is supported by funding from the NOAA Office of Global Programs for the Global Precipitation Climatology Project (GPCP) and by NASA via the Tropical Rainfall Measuring Mission (TRMM).

The permanent archive at GES DISC is supported by NASA's HQ Earth Science Data Systems (ESDS) Program.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

Downloads & Resources


Metadata Created Date November 12, 2020
Metadata Updated Date December 6, 2023

Metadata Source

Harvested from NASA Data.json

Graphic Preview

Panoply screenshot of Half-Hourly 4-km Merged IR Brightness Temperatures served from GES DISC OPeNDAP

Additional Metadata

Resource Type Dataset
Metadata Created Date November 12, 2020
Metadata Updated Date December 6, 2023
Identifier C1432254058-GES_DISC
Data First Published 2017-10-10
Language en-US
Data Last Modified 2017-10-10
Category GPM, geospatial
Public Access Level public
Bureau Code 026:00
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Citation John Janowiak, Bob Joyce, Pingping Xie. Andrey Savtchenko. 2017-12-30. GPM_MERGIR. Version 1. NCEP/CPC L3 Half Hourly 4km Global (60S - 60N) Merged IR V1. Greenbelt, MD. Archived by National Aeronautics and Space Administration, U.S. Government, Goddard Earth Sciences Data and Information Services Center (GES DISC). Digital Science Data.
Creator John Janowiak, Bob Joyce, Pingping Xie
Data Presentation Form Digital Science Data
Editor Andrey Savtchenko
Graphic Preview Description Panoply screenshot of Half-Hourly 4-km Merged IR Brightness Temperatures served from GES DISC OPeNDAP
Graphic Preview File
Harvest Object Id 9b89d34e-da6c-4e05-8e97-8c175d079ecb
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Homepage URL
Metadata Type geospatial
Old Spatial -180.0 -60.0 180.0 60.0
Program Code 026:001
Release Place Greenbelt, MD
Series Name GPM_MERGIR
Source Datajson Identifier True
Source Hash cc042b720baa62397379e53e153e337fa874efdaf4415df96e8ae89eca3ebece
Source Schema Version 1.1
Temporal 1998-01-01T00:00:00Z/2022-01-17T00:00:00Z

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