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Nimbus Temperature-Humidity Infrared Radiometer 11.5 µm Remapped Digital Data Daily L3, GeoTIFF, Version 1
This data set (NmTHIR115-3G) consists of daily, global composites of radiative temperatures obtained in the 11.5 µm window (10.5 µm - 12.5 µm) by the Temperature-Humidity Infrared Radiometer (THIR) on board the Nimbus 4 satellite. This window was used to measure cloud top or surface temperatures. Data files are GeoTIFF versions of the HDF-formatted equatorial projection file only from the Nimbus Temperature-Humidity Infrared Radiometer 11.5 µm Remapped Digital Data Daily L3, HDF5 (NmTHIR115-3H) data set.
Geographic Coverage
Spatial Coverage: |
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Spatial Resolution: |
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Temporal Coverage: |
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Temporal Resolution: | 1 day |
Parameter(s): |
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Platform(s) | NIMBUS-4 |
Sensor(s): | THIR |
Data Format(s): |
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Version: | V1 |
Data Contributor(s): | David Gallaher, G. Garrett Campbell |
Metadata XML: | View Metadata Record |
Data Citation
As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.
Gallaher, D. and G. Campbell. 2015. Nimbus Temperature-Humidity Infrared Radiometer 11.5 µm Remapped Digital Data Daily L3, GeoTIFF, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/NIMBUS/NmTHIR115-3G. [Date Accessed].Detailed Data Description
The THIR detected emitted thermal radiation in two windows: 6.7 µm (6.5 µm — 7.0 µm) and 11.5 µm (10.5 µm — 12.5 µm). This data set contains Nimbus-4 THIR 11.5 µm window data for the region between 60° N and 60° S. The corresponding THIR 6.7 µm window measurements are available as a separate data set here.
Data files are provided in Geographic Tagged Image File Format (GeoTIFF)
This section explains the file naming convention used for NmTHIR115-3G data files. Daily composites are divided into ascending/day (up) and descending/night (down) orbit halves. As such, two GeoTIFF files are available per solar day.
Example File Name: NmTHIR115-3G.DownIR.1970.04.13.G.tif
NmTHIR115-3G.[UpIR/DownIR].[yyyy].[mm].[dd].[p].tif
Refer to Table 1 for the valid values for the file name variables listed above.
Variable | Description |
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NmTHIR115-3G | Nimbus-4 THIR 11.5 µm window daily composite (GeoTIFF) |
UpIR/DownIR | Orbit half: Up (day) or Down (night), infrared temperature |
yyyy | Four-digit year |
mm | Month |
dd | Day |
p | Projection: G (equatorial) |
.tif | GeoTIFF file |
Data files typically about 4 MB.
- Northernmost Latitude: 60° N
- Southernmost Latitude: 60° S
- Easternmost Longitude: 180° E
- Westernmost Longitude: 180° W
Spatial Resolution
Roughly 20 km
Projection and Grid Description
Data are provided in a 20 km cylindrical equidistant projection. The grid was constructed by defining a 2000 east-west by 664 north-south global array at the equator to establish roughly 20 km x 20 km cells. Only the portion of the grid from 60° N to 60° S (2000 X 664) is saved for the final output.
Variable Description
The parameter of interest in this data set is infrared brightness temperature in the 11.5 µm window. See the Data Acquisition and Processing section of this document for details.
Software and Tools
Any GeoTIFF-compatible software package can be used to read and display this data set's files.
Data Acquisition and Processing
The THIR on the Nimbus 4 satellite transformed measured radiation into electrical voltages that were recorded on tape and played back when the satellite came within range of a receiving station. These data were then transmitted to the Goddard Space Flight Center (GSFC), where they were calibrated, converted to temperatures, and archived on 7-track, digital magnetic tapes. In 2013, the contents of these tapes were recovered and written to a binary tape emulation file format (TAP) for preservation. GES DISC, the NASA Goddard Earth Sciences Data and Information Services Center, maintains a Nimbus Overview page through which users can obtain the TAP files and historical Nimbus documentation such as instrument user guides and mission reports.
Processing Steps
To construct the daily composites, all reprocessed THIR swaths for each 24-hour period were accumulated from the Nimbus Temperature-Humidity Infrared Radiometer 11.5 µm Swath L1, HDF5 (NmTHIR115-1H) data set. When multiple observations were available in a grid cell, the observation closest to satellite nadir was selected.
The underlying THIR swath data have been corrected to minimize seemingly random alignment errors that caused cloud edges and land features to appear jagged. See Derivation Techniques and Algorithms in the NmTHIR115-1H documentation for details.
Error Sources
This data set was constructed from archival files at GES DISC. As such, they reflect the original THIR calibration and temperature conversion utilized in 1970. Furthermore, most of the mosaics have large areas of missing data because the Nimbus 4 project only captured select data based on operational considerations in the 1970-1971 time frame.
The realignment described in the preceding section improves the visual appearance of the data and better represents the shapes of clouds and coastlines. In regions with very little spatial information, for example where the measurements are very noisy or very uniform, the shifts offer little or no improvement.
The Nimbus 4 Temperature-Humidity Infrared Radiometer (THIR) was a two-channel scanning radiometer designed to detect emitted thermal radiation in two windows: 6.7 µm (6.5 µm — 7.0 µm) and 11.5 µm (10.5 µm — 12.5 µm). The 6.7 µm window operated primarily at night and was used to map the distribution of water vapor in the upper troposphere and stratosphere. The 11.5 µm channel operated both day and night and measured cloud top or surface temperatures.
The Nimbus 4 instrument utilized a single scan mirror which rotated at 48 rpm and was inclined 45° to the axis of rotation to scan perpendicular to the flight path. The field of view scanned across the earth from east to west in daytime and west to east at night, traveling northward and southward respectively. Incoming energy was collected by the mirror and then focused into a dichromatic beam splitter which divided the energy spectrally and spatially into the two channels. Both channels transformed the received radiation into an electrical (voltage) output with an information bandwidth of 0.5 Hz to 120 Hz for the 6.7 µm channel and 0.5 Hz to 360 Hz for the 11.5 µm channel. The data were recorded on tape and subsequently played back to a ground acquisition station.
The THIR intially operated successfully but failed on January 11, 1971 (orbit 3731). It was restarted several times thereafter for very short periods before finally ceasing all operations in August 1971. For additional information about the Nimbus THIR, see the NASA National Space Science Data Center Temperature-Humidity Infrared Radiometer (THIR) Web page.
Version (Date) | Details |
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V1 (24 November, 2015) | Initial release. |
References and Related Publications
Contacts and Acknowledgments
Investigators
David Gallaher
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
G. Garrett Campbell
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
The Nimbus Data Rescue Project was supported by NASA contract #NNG08HZ07C as a subtask to NSIDC at the University of Colorado. The PIs also wish to thank Dennis Wingo and Matt Sandler who contributed to this project.
Document Information
DOCUMENT CREATION DATE
November 2015
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