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This data set provides daily, near-real-time Special Sensor Microwave/Imager (SSM/I) and Special Sensor Microwave Imager/Sounder (SSMIS) brightness temperatures in the Equal-Area Scalable Earth-Grid (EASE-Grid). The data set consists of gridded data in two projections: Northern Hemisphere and Southern Hemisphere. The data lag by one day and provide 270 days of near-real-time data. The spatial resolution is 25 km for all channels. Data are contained in flat binary files and are available via FTP.
These data may contain errors and are not suitable for time series, anomalies, or trends analyses. Near-real-time products do not undergo quality assessment and are therefore not intended for operational use.
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.
The following example shows how to cite the use of this data set in a publication. List the principal investigators, year of data set release, data set title, dates of data you used, publisher: NSIDC, and digital media.
Brodzik, M. and R. Armstrong. 2008. Near-Real-Time DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.
|Data format||Brightness Temperature Files: Flat binary, little-endian, 2-byte unsigned, compressed (Gzip)
Time Files: Flat binary, little-endian, 2-byte signed, compressed (Gzip)
|Spatial coverage and resolution||
Northern and Southern Hemispheres
25 km resolution for all channels (19, 22, 37, 85 and 91GHz)
Note: The high-frequency 85.5 GHz channel on SSM/I has been replaced by a 91 GHz channel on SSMIS. Users should note that the different frequency will affect any products that employ a high frequency channel. Any such products should be evaluated for the impact of the different frequency and adjustments may be necessary for consistent products.
|Temporal coverage and resolution||Past 270 days
|Tools for accessing data||IDL Tools|
Northern Hemisphere EASE-Grid
Southern Hemisphere EASE-Grid
|File naming convention||ID2-Fxx-HHYYYYDDDP.CCC.gz|
|File size||Gzipped Brightness Temperature Files: 133 KB - 417 KB per file
Gzipped Time Files: 9.7 KB - 30 KB per file
|Parameter(s)||Brightness temperatures (0.1 K precision)|
|Procedures for obtaining data||Available via FTP|
Mary J. Brodzik
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
Brightness temperature data are contained in flat binary files (little-endian) with one array per file consisting of 2-byte integer arrays of brightness temperatures in tenths of kelvins.
Each brightness temperature file contains gridded data for a single sensor channel and polarization; they are derived from either ascending or descending orbits (for example, 37 GHz, horizontal, ascending) for one day. There are 18 brightness temperature files per day for each projection. There are two files for each day (ascending and descending orbits) for each projection and for each sensor channel (frequency and polarization).
Time data are contained in 2-byte, signed integer arrays. Time data are minutes since 00:00 Coordinated Universal Time (UTC) of the date of the enclosing file. Each time file represents the corresponding time of the swath sample used for the interpolation of the given grid cell, for either ascending or descending orbits for that day. There are two time files per day (ascending and descending passes) for a given projection, both at 25 km resolution.
Data are available on the FTP site and all files reside within one directory, the nsidc0342_nrt_ease_grid_tbs directory.
Files are named according to the following convention and as described in Table 1:
|ID2||Indicates that this data was interpolated with an inverse distance squared method.|
|Fxx||DMSP satellite ID (f13: DMSP-F13; f17: DMSP-F17)|
|HH||Hemisphere (NL: Northern, SL: Southern)|
|DDD||3-digit day of year|
|P||Direction of pass (A: ascending, D: descending)|
|CCC||Indicates channel and polarization or time file:
19H: 19 GHz Horizontal
19V: 19 GHz Vertical
22V: 22 GHz Vertical
37H: 37 GHz Horizontal
37V: 37 GHz Vertical
85H: 85 GHz Horizontal (SSM/I data only)
85V: 85 GHz Vertical (SSM/I data only)
91H: 91 GHz Horizontal (SSMIS data only)
91V: 91 GHz Vertical (SSMIS data only)
tim: Time file
|gz||Indicates that this is a gzipped file|
Gzipped Brightness Temperature Files: 133 KB to 417 KB per file
Gzipped Time Files: 9.7 KB to 30 KB per file
These data files are provided in two different spatial coverages: Northern Hemisphere and Southern Hemisphere. Please see the Grid Extent Table on the EASE-Grid: A Versatile Set of Equal-Area Projections and Grids Web page for specific latitude and longitude values.
The spatial resolution for all channels is 25 km.
The SSM/I azimuthal EASE-Grids are equal-area projections: one for the Northern and one for the Southern Hemisphere. Please see the EASE-Grid: A Versatile Set of Equal-Area Projections and Grids for more information on the EASE-Grid.
This data set provides near-real-time SSM/I and SSMIS brightness temperatures for the past 270 days with a one day lag period. The resolution is daily.
The parameter of this data set is brightness temperature.
Please refer to the Parameter or Variable section of the DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures guide document for more information on the parameters in this data set.
Due to the near-real-time nature of this data set, no quality assessment is performed.
Data are available via FTP.
Geolocation tools for this data set are available via the
EASE-Grid Data Geolocation Tools Web
These data were acquired using the SSM/I instrument on the DMSP-F13 platform and the SSMIS instrument on the DMSP-F17 platform. For more information about the these instruments, please see the SSM/I Instrument Description and SSMIS Instrument Description Web pages.
The DMSP SSM/I and SSMIS instruments measure passive microwave radiances. For a detailed description of how the instruments obtain these measurements, refer to the SSM/I Instrument Description and SSMIS Instrument Description Web pages.
Input data are acquired via FTP. The F13 input data were acquired from NASA's Global Hydrology Research Center (GHRC) and F17 input data are acquired from NOAA's National Environmental Satellite, Data, and Information Service (NESDIS).
The DMSP-F13 satellite that has been central to our brightness temperature products for the past several years is nearing the end of its mission and is no longer a reliable resource for our brightness temperature products. As is standard data practice, we have transitioned to a newer sensor. As of 01 September 2009, NSIDC has switched its SSM/I processing stream from the DMSP-F13 satellite to SSMIS data from the DMSP-F17 satellite. For data continuity, F17 data have been acquired and processed back to 01 August 2009 to allow for a one-month overlap period for the two sensors. The F13 data will remain available via FTP until they age off and are eventually replaced by the F17 data. However, NSIDC recommends using the F13 near-real-time data for intercomparison purposes only. SSMIS data from the DMSP-F17 satellite are used for the current near-real-time product.
Regarding the F17 data, users should note a difference in the high frequency channel. The SSMIS sensor is similar to the SSM/I sensor and has the same low frequency channels: dual-polarized 19 GHz and 37 GHz channels, and a vertically polarized 22 GHz channel. However, the high-frequency 85.5 GHz channel on SSM/I has been replaced by a 91 GHz channel on SSMIS. Users should note that the different frequency will affect any products that employ a high frequency channel. Any such products should be evaluated for the impact of the different frequency and adjustments may be necessary for consistent products.
These data have been interpolated with an inverse distance-squared (ID2) interpolation.
These data are intended as a near-real-time extension of the DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures data set. Data processing is the same as for DMSP SSM/I-SSMIS Pathfinder Daily EASE-Grid Brightness Temperatures with the following exceptions:
For information on the processing of these data, please see the Processing Steps section in the DMSP SSM/I Pathfinder Daily EASE-Grid Brightness
Brodzik, M. J. and K. W. Knowles. 2002. "EASE-Grid: A Versatile Set of Equal-Area Projections and Grids" in M. Goodchild (Ed.) Discrete Global Grids. Santa Barbara, California USA: National Center for Geographic Information & Analysis.
Table 2 lists related documents that are available from NSIDC.
|All About EASE-Grid||Web page that describes EASE-Grid.||http://nsidc.org/data/ease/index.html|
|EASE-Grid: A Versatile Set of Equal-Area Projections and Grids||Technical Report on EASE-Grid||http://nsidc.org/data/ease/ease_grid.html|
|NSIDC's EASE-Grid Geolocation Tools||Web page that provides descriptions of each EASE-Grid geolocation tools for the various data sets.||http://nsidc.org/data/ease/tools.html|
|Special Sensor Microwave Imager (SSM/I)||Web page with SSM/I instrument description||http://nsidc.org/data/docs/daac/ssmi_instrument.gd.html|
|EASE-Grid Image Gallery||Sampler image gallery of SSM/I Level 3 Brightness Temperatures.||http://nsidc.org/data/docs/daac/nsidc0032_ssmi_ease_tbs/gallery/index.html|
|Frequently Asked Questions||NOAA/NASA Pathfinder SSM/I Level 3 EASE-Grid Brightness Temperatures FAQs||http://nsidc.org/data/docs/faqs/ssmi_ease_faq.html|
Table 3 lists acronyms that are used in this document.
|DMSP||Defense Meteorological Satellite Program|
|EASE-Grid||Equal-Area Scalable Earth-Grid|
|EOS||Earth Observing System|
|FAQ||Frequently Asked Question|
|FTP||File Transfer Protocol|
|GHRC||Global Hydrology Research Center|
|NASA||National Aeronautics and Space Administration|
|NESDIS||National Environmental Satellite, Data, and Information Service|
|NOAA||National Aeronautics and Space Administration|
|NSIDC||National Snow and Ice Data Center|
|RSS||Remote Sensing Systems|
|SSM/I||Special Sensor Microwave/Imager|
|SSMIS||Special Sensor Microwave Imager/Sounder|
|URL||Uniform Resource Locator|