Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS, Version 2

Table of Contents

  1. Detailed Data Description
  2. Data Access and Tools
  3. Data Acquisition and Processing
  4. References and Related Publications
  5. Contacts and Acknowledgments
  6. Document Information

Citing These Data

We kindly request that you cite the use of this data set in a publication using the following citation. For more information, see our Use and Copyright Web page.

Comiso, J. 2000, updated 2014. Bootstrap Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS. Version 2. [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center.

Overview

Platform

NIMBUS-7, DMSP-F8, -F11, -F13, -F17

Sensor

SMMR, SSM/I-SSMIS

Spatial Coverage

North and south polar regions

Spatial Resolution

25 km

Temporal Coverage

26 October 1978 – 31 December 2013

Temporal Resolution

Daily (every other day for SMMR data), monthly

Parameters

Sea ice concentration

Data Format

Flat binary 2-byte integer; little-endian byte order; scaled by 10

Metadata Access

View Metadata Record

Version

V2. See the Version History section of this document for version information.

Data Access

FTP

1. Detailed Data Description

This sea ice concentration data set was derived using measurements from the Scanning Multichannel Microwave Radiometer (SMMR) on the Nimbus-7 satellite and from the Special Sensor Microwave/Imager (SSM/I) sensors on the Defense Meteorological Satellite Program's (DMSP) -F8, -F11, and -F13 satellites. Measurements from the Special Sensor Microwave Imager/Sounder (SSMIS) aboard DMSP-F17 are also included. The data set has been generated using the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) Bootstrap Algorithm with daily varying tie-points. Daily (every other day prior to July 1987) and monthly data are available for both the north and south polar regions. Data are gridded on the SSM/I polar stereographic grid (25 x 25 km) and provided in two-byte integer format.

Important

Users should acquire the entire Version 2 data set in order to update their time series. For more information, refer to the Version History section of this document.

Format

Data files are stored in the original Goddard Space Flight Center (GSFC) flat binary two-byte integer format, use the little-endian byte order convention, and are scaled by a factor of 10. An individual image of daily or monthly averaged data constitutes a granule in the Bootstrap sea ice concentration time series.

File and Directory Structure

Data on the FTP site are arranged into two subdirectories, north and south. Within the directories for each hemisphere are two more subdirectories; one for the daily files and one for the monthly files labeled daily and monthly, respectively. The daily directory is further subdivided into directories by year. Monthly files are located in the monthly directory with no further subdivision. Figure 1 shows the directory structure.

Data Directory Structure

Figure 1. File Organization

File Naming Convention

Daily Files

Daily files are named according to the following convention:

bt_YYYYMMDD_SSS_vVV_H.bin

where:

Table 1. Daily Files Naming Convention
bt indicates that this file was created using the bootstrap algorithm
.bin indicates that this file is in binary format
YYYY = 4-digit year
MM = 2-digit month
DD = 2-digit day
SSS = 3-character sensor name (n07 for Nimbus-7 SMMR; f08, f11, or f13 for DMSP SSM/I sensors; f17 for the DMSP SSMIS sensor)
VV = 2-digit version number (for example, 02)
H = Hemisphere (n for Northern, s for Southern)

For example, bt_20060901_f13_v02_n.bin contains the daily Northern Hemisphere SSM/I F13 data for 01 September 2006.

Monthly Files

Monthly files are named according to the following convention:

bt_YYYYMM_SSS_vVV_H.bin

where:

Table 2. Monthly Files Naming Convention
bt indicates that this file was created using the bootstrap algorithm
.bin indicates that this file is in binary format
YYYY = 4-digit year
MM = 2-digit month
SSS = 3-character sensor name (n07 for Nimbus-7 SMMR; f08, f11, or f13 for DMSP SSM/I sensors; f17 for the DMSP SSMIS sensor)
VV = 2-digit version number (for example, 02)
H = Hemisphere (n for Northern, s for Southern)

For example, bt_200609_f13_v02_n.bin contains the monthly Northern Hemisphere SSM/I F13 data for September 2006.

File Size

Northern Hemisphere files are approximately 266 KB. Southern Hemisphere files are approximately 205 KB.

Volume

The entire data set is approximately 7.6 GB.

Spatial Coverage

Data set coverage includes the northern and southern polar regions. For a detailed description, see the SSM/I Polar Spatial Coverage Maps section of the Polar Stereographic Projections and Grids Web site.

SSM/I and SSMIS instrument coverage is global, except for circular sectors centered over the North Pole, 311 km in radius, located poleward of 87.2°. These sectors are never measured due to orbit inclination. The 50° scan pattern provided a swath width of 780 km at the Earth's surface. The spatial resolutions at the various frequencies ranged from approximately 27 km at 37 GHz to 148 km at 6.6 GHz. For more information, see the Special Sensor Microwave Imager (SSM/I) description Web page. The measurement footprint size or effective field of view (FOV) varies by frequency, as shown in the following table.

Table 3. SSM/I-SSMIS
Frequency Footprint Size
19.3 GHz 70 x 45 km
22.2 GHz 60 x 40 km
37.0 GHz> 38 x 30 km

SMMR instrument coverage is global, except for circular sectors centered over the North Pole, approximately 611 km in radius, located poleward of 84.5°. These sectors are never measured due to orbit inclination. The 50° scan pattern provided a swath width of 780 km at the Earth's surface. The spatial resolutions at the various frequencies ranged from approximately 27 km at 37 GHz to 148 km at 6.6 GHz. For more information see the Scanning Multi-channel Microwave Radiometer (SMMR) description page. The measurement footprint size varies by frequency, as shown in the following table.

Table 4. SMMR
Frequency Footprint Size
6.6 GHz 148 x 95 km
10.7 GHz 91 x 59 km
18.0 GHz 55 x 41 km
21.0 GHz 46 x 30 km
37.0 GHz 27 x 18 km

Spatial Resolution

Sea ice concentrations are provided at a resolution of 25 km.

Projection and Grid Description

For more information, see Polar Stereographic Projections and Grids. The grid size varies depending on the region, as shown in the following table.

Table 5. Grid Size
Region Columns Rows
North 304 448
South 316 332

Temporal Coverage

Bootstrap sea ice concentration data are available for 26 October 1978 through 31 December 2013.

Temporal Resolution

SMMR data were collected every other day. (The scanner operated only on alternate days, due to spacecraft power limitations). Major data gaps occurred in August 1982 (4, 8, and 16 August) and 1984 (13 through 23 August) for both polar regions. Monthly means are generated by averaging all available files for each individual month, excluding pixels of missing data. Data were interpolated where missing pixels were present so that no areas of missing data remained.

SSM/I and SSMIS data are collected daily. Ice concentrations are provided for each day of data and as monthly means. Monthly mean files are generated by averaging all available daily files for each individual month, excluding pixels of missing data. A major data gap in the SSM/I data occurs from 03 December 1987 to 13 January 1988.

Parameter or Variable

The data set consists of sea ice concentration derived from gridded brightness temperatures. Sea ice concentrations range from 0 to 100%. Please see the Parameter Range section for more details.

Parameter Range

Data are stored as two-byte integers representing sea ice concentration values. The sea ice concentration data values are packed into integer format by multiplying the original sea ice concentration values by 10 (divide stored value by 10 to get the percent). The sea ice concentration values range from 0 to 1000. Land is registered as 1200 and the Northern Hemisphere hole (a region of the North Pole that is not measured due to orbit inclination, see the Spatial Coverage section) is registered as 1100.

Sample Data Record

The following is a sample data record from the Northern Hemisphere monthly data.

 837  887  924 971  971 992 980 975 974 964 980 965 936 972 968 986
 982  987  978 984  988 965 980 972 981 985 992 988 989 983 993 986
 985  984  982 983  982 981 974 990 982 983 978 977 983 987 981 992
 985  979  978 982  981 969 966 972 977 984 973 976 980 970 972 977
 980  984  980 982  977 973 973 969 968 972 980 951 887 877 928 936
1200 1200 1200 969 1200 951 956 980 980 980 975 982 982 961 937 863
 791  710  706 706  678

Error Sources

Sensitivity analysis of potential errors associated with the retrieval of sea ice products has been discussed previously (for example see Comiso et al. 1997 and other references associated with the NASA Team Algorithm sea ice products). Sea ice concentration errors are difficult to quantify because sea ice is an evolving ice cover and does not have uniform physical and radiative characteristics throughout the ice pack. The emissivity of sea ice is known to change as the ice cover develops from grease ice to nilas, pancake to young ice, or first year ice to multiyear ice (for definitions of these types of ice, see the NSIDC glossary page). The line AD in the scatter plot that provides the sea ice tie-point in the Bootstrap Algorithm corresponds to 100% ice for the relatively thick ice types such as first year or multiyear ice. Areas with 100% of thinner ice types are often estimated to have ice concentrations as low as 80% due to lower emissivities (Comiso et al. 1992). In the summer, retrievals in the Arctic could have biases caused by meltponding effects (Comiso and Kwok 1996).

Inside the ice pack, observations from helicopter and aircraft flights typically show very high sea ice concentrations with some 5 to 10% of the leads covered by nilas or pancake ice. The frequency distribution of sea ice concentration in highly consolidated ice areas has a standard deviation of about 3%, which includes sea ice cover with concentrations of less than 100%. Overall, retrieval accuracy is estimated to be approximately 5 to 10% except in some unusual cases, such as the presence of a large fraction of thin ice or meltponding within the pixel and the presence of stormy weather conditions, especially near the ice edge. Limited comparative analysis with high resolution instruments and other measurements confirm this, but more extensive validation in a greater number of places over all of the seasons would provide more accurate error assessments.

Quality Assessment

Although most bad data are easily identifiable and removed with little ambiguity, human judgments must be made and applied consistently to the time series data. While efforts were made to minimize errors in judgment and inconsistencies, the resulting data set is not perfect. Nevertheless, the data provider feels that these maps are suitable for some types of research studies, such as basin-scale trend analysis, model inputs, and some regional studies. They are less useful in evaluating conditions on a specific day in a localized region.

NSIDC staff visually checked the entire set of data files, including file structure, comparisons to existing SMMR- and SSM/I-derived sea ice concentration grids, and information files and examination of data quality.

Please note that in this document, a large fraction of the text was supplied by the data set provider. It may include qualitative judgments and statements by the provider and does not necessarily represent endorsements or imply that independent assessments have been performed by NSIDC staff.

Limitations of the Data

Basic limitations arise from the sensor resolution, temporal coverage, and algorithm assumptions and characteristics. Users should review the information provided on fields of view, temporal sampling, and algorithm characteristics.

Particular care is needed in interpreting the sea ice concentrations during summer when melt is underway and in regions where new sea ice makes up a substantial part of the sea ice cover. As noted, some residual errors remain due to sensor differences and to weather effects along with mixing of ocean and land area within the sensor field of view.

No data coverage is available for regions poleward of 84.5° N for SMMR and 87.2° N for SSM/I or SSMIS due to the inclination of the orbits. SMMR data were acquired every other day, while SSM/I data were acquired daily. SSMIS data are also acquired daily.

2. Data Access and Tools

Data Access

Data are available via FTP.

Software and Tools

Fortran tools are provided which extract the sea ice concentration files and geolocate the data. Sample Fortran code is provided for reading and displaying these sea ice concentration data.

Sample Interactive Data Language (IDL) commands to read and display sea ice grids and latitude/longitude grids are provided via the IDL commands text file. In addition, IDL tools to extract the sea ice concentration files and geolocate the data, as well as masking tools that limit the influence of non-sea ice brightness temperatures, are provided.

The NSIDC DataViewer, written in IDL, is also available for use with this data set. The DataViewer is an interactive tool for viewing and displaying satellite images from select NSIDC passive microwave data sets. For more information and access to this tool, refer to the dataviewer.tar.gz section of the Polar Stereographic Data Display Tools Web page.

Table 6 lists the tools that can be used with this data set. For a comprehensive list of all polar stereographic tools, see the Polar Stereographic Data Tools Web page.

Table 6. Tools for this Data Set
Tool Type Tool File Name(s)
Data Extraction extract_ice.pro
Data Display dataviewer.tar.gz
Geocoordinate dataviewer.tar.gz
locate.for
mapll.for and mapxy.for
psn25lats_v3.dat and pss25lats_v3.dat
psn25lons_v3.dat and pss25lons_v3.dat
Pixel-Area psn25area_v3.dat and pss25area_v3.dat
Land Masks gsfc_25n.msk and gsfc_25s.msk
coast_25n.msk and coast_25s.msk
ltln_25n.msk and ltln_25s.msk
pole_n.msk
Region Masks region_n.msk and region_s.msk

3. Data Acquisition and Processing

Satellite passive microwave sensors provide global radiance measurements that may be used to map, monitor, and study Arctic and Antarctic polar sea ice. The microwave data used for this sea ice concentration data set spans over 25 years, starting with the launch of the SMMR instrument on NASA's Nimbus-7 in 1978 and continuing with the DMSP SSM/I series beginning in 1987.

Sea ice concentrations are generated using brightness temperatures (Tbs) derived from SMMR and SSM/I radiances. The goal in the creation of the data set is to produce a long-term, consistent data set in which sea ice extent and area differences between the sensors are reduced that could serve as a baseline for future measurements. The Bootstrap data set provides improved consistency between sensors and enhanced removal of weather and land contamination.

The Bootstrap data set includes gridded daily and monthly averaged sea ice concentrations (every-other-day for the SMMR data) for both the north and south polar regions beginning 26 October 1978 through the most current processing.

Algorithms designed to estimate sea ice concentration using passive microwave data frequently do not work well over open ocean. When applied, instead of predicting the expected zero value, the algorithms predict sea ice concentration values as high as 35 percent, particularly in regions with excessive winds and stormy weather. A climatological sea surface temperature mask was applied to remove pixels from regions where the ocean surface is above freezing. Also, land contamination (false ice along the coast due to pixels containing a mixture of land and ocean) were removed using a filter adapted from Cho et al. (1996). Even with these quality-control measures, some residual sea ice concentrations remain in the open ocean and along the coast.

Theory of Measurements

The SMMR and SSM/I instruments are dual-polarized and multi-frequency microwave radiometers that sense emitted microwave radiation at an incidence angle of about 53° and an altitude of about 800 km. At microwave frequencies, the observed radiance varies linearly with the temperature of the emitting material, according to the Rayleigh-Jeans law, and is usually expressed in terms of brightness temperature. The constant of proportionality in the linear relationship is the emissivity, which provides information about the electrical and physical properties of the material itself. The observed brightness temperatures come primarily from the Earth's surface with some contributions from the atmosphere and outer space. Depending on frequency and polarization, the brightness temperature is affected by changing surface, subsurface, and atmospheric conditions. The multichannel capability allows for the discrimination of different surfaces and atmospheric effects and allows for the development of algorithms that provide a range of geophysical information about the surface.

Sensor/Platform Description

Please refer to the following documents for details on sensors and platforms:

Sensors

Scanning Multi-channel Microwave Radiometer (SMMR)

Special Sensor Microwave Imager (SSM/I)

Special Sensor Microwave Imager (SSMIS)

Platforms

Nimbus 7 Spacecraft System

Defense Meteorological Satellite Program (DMSP) Satellite F8

Defense Meteorological Satellite Program (DMSP) Satellite F11

Defense Meteorological Satellite Program (DMSP) Satellite F13

Defense Meteorological Satellite Program (DMSP) Satellite F17

Data Acquisition Methods

Four sets of satellite data are used to create the Bootstrap sea ice data stream:

  • Nimbus-7 SMMR, data range: 26 October 1978 through 20 August 1987
  • DMSP-F08 SSM/I, data range: 9 July 1987 through 18 December 1991
  • DMSP-F11 SSM/I, data range: 3 December 1991 through 31 December 1996
  • DMSP-F13 SSM/I, data range: 5 May 1995 through 31 December 2007
  • DMSP-F17 SSMIS, data range: 1 January 2008 through the most current processing

SMMR

Sea ice concentrations were processed by GSFC using SMMR brightness temperatures. The SMMR brightness temperatures were processed and quality checked at GSFC (Gloersen et al. 1992).

SSM/I-SSMIS

Bootstrap sea ice concentrations were processed at GSFC using DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures from NSIDC. Processing of DMSP-F17 brightness temperatures is ongoing. For more information on the brightness temperatures, see the DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures documentation.

Derivation Techniques and Algorithms

Sea ice concentrations for this data set were derived from a revised Bootstrap algorithm which uses a different set of tie-points and adjustments. For algorithm background, please see the Enhanced Sea Ice Concentrations from Passive Microwave Data document (Comiso and Nishio 2008).

Processing Steps

With Version 2 of the data set (released September 2007), adjustments were made to the tie-points to make the ongoing SMMR-SSM/I time series consistent with the AMSR-E Bootstrap algorithm product (see Enhanced Sea Ice Concentrations from Passive Microwave Data for further information). In addition to the inter-calibration of the SMMR-SSM/I with AMSR-E, the algorithm was adjusted in the Antarctic to remove negative bins of a few percent ice concentration. Other minor changes were also made for Version 2. Full documentation of the Version 2 data is available in the Enhanced Sea Ice Concentrations from Passive Microwave Data document. Users should thoroughly examine the Version 2 documentation before using the data.

Interpolation

Data were interpolated in areas with missing pixels according to the following steps. First, data were spatially interpolated only for isolated empty pixels. An empty pixel was replaced by the average of four good surrounding pixels, or if four good pixels were not available, then a smaller number of pixels was selected. Second, a time interpolation was applied to the spatially interpolated map. Time interpolation was based on a weighting scheme; the closer the good data were in time, the higher the weighted value. For each empty pixel, the algorithm searched forward in time for a good pixel, and backward in time for a second good pixel. The algorithm determined how many days ahead and behind the two good pixels occurred and calculated the weight of each pixel. A weighted average of the two good pixels was then calculated, and the result was used for the empty pixel. During the SSM/I period, most temporal interpolations were conducted using only adjacent days. During the SMMR period, particularly in 1986 when larger gaps were present, temporal interpolations had separations of more days.

Version History

Table 7 outlines the processing and algorithm history for this product.

Table 7. Description of Version Changes
Version Date Description
V2 September 2007 Changes to this version include:
  • Adjusted tie-points to be consistent with the AMSR-E Bootstrap algorithm
  • Reprocessed entire SMMR-SSM/I time series

Important: Because Version 2 is inter-calibrated with AMSR-E, it is not compatible with Version 1 of this data set. Users should acquire the entire Version 2 data set in order to update their time series. This product is also not consistent with the NSIDC-produced Bootstrap Product, the DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures. For further information on Version 2 data processing, see Enhanced Sea Ice Concentrations from Passive Microwave Data.

V1 January 1996 Original version of data. For information on the Version 1 data processing, see the Bootstrap Sea Ice Concentrations Version 1 Processing Steps Web page.

4. References and Related Publications

The following references were used in this document:

Cho, K., N. Sasaki, H. Shimoda, T. Sakata, and F. Nishio. 1996. Evaluation and Improvement of SSM/I Sea Ice Concentration Algorithms for the Sea of Okhotsk. Journal Remote Sensing of Japan 16(2):47-58.

Comiso, J. C., and F. Nishio. 2008. Trends in the Sea Ice Cover Using Enhanced and Compatible AMSR-E, SSM/I, and SMMR Data. Journal of Geophysical Research 113, C02S07, doi:10.1029/2007JC0043257.

Comiso, J. C., D. Cavalieri, C. Parkinson, and P. Gloersen. 1997. Passive Microwave Algorithms for Sea Ice Concentrations: A Comparison of Two Techniques. Remote Sensing of the Environment 60(3):357-84.

Comiso, J. C., and R. Kwok. 1996. The Summer Arctic Sea Ice Cover from Satellite Observations. Journal of Geophysical Research 101(C2):28,397-416.

Comiso, J. C. 1995. SSM/I Concentrations Using the Bootstrap Algorithm. NASA Reference Publication 1380. 40 pages.

Comiso, J. C, T. C. Grenfell, M. Lange, A. Lohanick, R. Moore, and P. Wadhams. 1992. Microwave Remote Sensing of the Southern Ocean Ice Cover. Microwave Remote Sensing of Sea Ice, ed. Frank Carsey. Washington D.C.: American Geophysical Union. 243-59.

Comiso, J. C. and C. W. Sullivan. 1986. Satellite Microwave and In-Situ Observations of the Weddell Sea ice Cover and its Marginal Ice Zone. Journal of Geophysical Research 91(C8):9,663-81.

Comiso, J. C. 1984. Characteristics of Winter Sea Ice from Satellite Multispectral Microwave Observations. Journal of Geophysical Research 91(C1):975-94.

Comiso, J. C., S. F. Ackley, and A. L. Gordon. 1984. Antarctic Sea Ice Microwave Signature and Their Correlation with In-Situ Ice Observations. Journal of Geophysical Research 89(C1):662-72.

Gloersen P., W. Campbell, D. Cavalieri, J. Comiso, C. Parkinson, H. J. Zwally. 1992. Arctic and Antarctic Sea Ice, 1978-1987: Satellite Passive Microwave Observations and Analysis. NASA Special Publication 511.

Maslanik, J. A. 1992. Effects of Weather on the Retrieval of Sea Ice Concentration and Ice Type from Passive Microwave Data. International Journal of Remote Sensing 13(1):37-54.

National Snow and Ice Data Center. 1992. DMSP SSM/I Brightness Temperature and Sea Ice Concentration Grids for the Polar Regions on CD-ROM - User's Guide. NSIDC Special Report - 1. 222 pp.

Parkinson, C. L., D. J. Cavalieri, P. Gloersen, H. J. Zwally, and J. C. Comiso, 1999.  Arctic Sea Ice Extents, Areas, and Trends, 1978-1996. Journal of Geophysical Research 104(C9), 20,837-20,856.

Parkinson, C. L., J. C. Comiso, H. J. Zwally, D. J. Cavalieri, P. Gloersen, and W. J. Campbell. 1987. Arctic Sea Ice 1973-1976 from Satellite Passive Microwave Observations. NASA Special Publication 489.

Pearson, F. 1990. Map Projections: Theory and Applications. Boca Raton, FL:CRC Press. 372 pages.

Snyder, J. P. 1987. Map Projections - A Working Manual. U.S. Geological Survey Professional Paper 1395. Washington, D.C.:U.S. Government Printing Office. 383 pages.

Snyder, J. P. 1982. Map Projections used by the U.S. Geological Survey. U.S. Geological Survey Bulletin 1532.

Zwally, H. J., J. C. Comiso, C. L. Parkinson, W. J. Campbell, F. D. Carsey, and P. Gloersen. 1983. Antarctic Sea Ice 1973-1976 from Satellite Passive Microwave Observations. NASA Special Publication 459.

The following related documents are available on the NSIDC Web site:

Table 8. Related Documents
Document Description URL
Enhanced Sea Ice Concentrations from Passive Microwave Data Bootstrap algorithm description http://nsidc.org/data/docs/daac/nsidc0079_bootstrap_seaice/docs/Bootstrap_Algorithm_Revised07.pdf
Polar Stereographic Projections and Grids Grid description http://nsidc.org/data/grids/ps_grid.html
Special Sensor Microwave Imager (SSM/I) SSM/I instrument description http://nsidc.org/data/docs/daac/ssmi_instrument.gd.html
Scanning Multi-channel Microwave Radiometer (SMMR) SMMR instrument description http://nsidc.org/data/docs/daac/smmr_instrument.gd.html
Bootstrap Sea Ice Concentrations Version 1 Processing Steps Version 1 processing description http://nsidc.org/data/docs/daac/nsidc0079_bootstrap_seaice/processing_steps_V1.html

Related Data Collections

  • Sea Ice Trends and Climatologies from SMMR and SSM/I-SSMIS
    NSIDC provides a suite of value-added products to aid in investigations of the variability and trends of sea ice cover. These products provide users with information about sea ice extent, total ice covered area, ice persistence, monthly climatologies of sea ice concentrations, and ocean masks.
  • DMSP SSM/I-SSMIS Daily Polar Gridded Brightness Temperatures
    NSIDC produces daily gridded brightness temperature (Tb) data from orbital (swath) data generated by SSM/I mounted on the DMSP F8, F11, and F13 platforms. The gridded brightness temperatures are distributed in polar stereographic projection.
  • Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I-SSMIS Passive Microwave Data
    This data set is generated from brightness temperature data derived from the Nimbus-7 SMMR and DMSP F8, F11, and F13 SSM/I radiances at a grid cell size of 25 x 25 km. The data are provided in the polar stereographic projection.
  • Sea Ice Index
    The images in the Sea Ice Index data set depict average ice conditions, estimated using satellite passive microwave data for the most recent month available, as well as snapshots of trends and anomalies that compare these recent conditions with the mean for the month.
  • Sea Ice Data
    This site offers a summary of sea ice data derived from passive microwave sensors and other sources and is useful for users who want to compare characteristics of various sea ice products to understand their similarities and differences. This site also provides links to tools for passive microwave data and a list of other sea ice resources.

5. Contacts and Acknowledgments

Investigator

Josefino C. Comiso
Oceans and Ice Branch, Code 971
NASA Goddard Space Flight Center
Greenbelt, MD 20771 USA

Technical Contact

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
e-mail: nsidc@nsidc.org

6. Document Information

Acronyms and Abbreviations

The following acronyms and abbreviations are used in this document.

Table 9. Acronyms and Abbreviations
Acronym Description
AMSR-E Advanced Microwave Scanning Radiometer - Earth Observing System
DMSP Defense Meteorological Satellite Program
FTP File Transfer Protocol
GHz Gigahertz
GSFC Goddard Space Flight Center
IDL Interactive Data Language
NASA National Aeronautics and Space Administration
NSIDC National Snow and Ice Data Center
SMMR Scanning Multichannel Microwave Radiometer
SSM/I Special Sensor Microwave Imager
SSMIS Special Sensor Microwave Imager/Sounder
Tb(s) Brightness Temperature(s)
URL Uniform Resource Locator

Document Creation Date

January 1999

Document Revision Date

May 2014

Document URL

http://nsidc.org/data/docs/daac/nsidc0079_bootstrap_seaice.gd.html