Service Interruption

In this Issue



Issue 2, Summer 1992


The Third Meeting of the Steering Group for the WMO Project "Global Sea Ice Data Bank" was held in the Congress Hall of the Arctic and Antarctic Research Institute, St. Petersburg, Russia, 20-24 July 1992. In attendance were: Roger Barry and Vincent Troisi - WDC-A; M. Krasnoperov - WMO; A. Bushuyev, I. Frolov, V. Stepanov, V. Smolyanitsky, Yu. Scherbakov - AARI.

The principal topics of discussion were:

  1. Data exchange between WDC-A and AARI, and
  2. the Sea Ice Grid (SIGRID) format and proposed modifications.

Data Exchange-NSIDC and AARI

Data in the SIGRID format have been received at AARI under the framework of the WMO Project, Global Data Bank. A work plan and schedule for the exchange of these data was completed; it was agreed that the exchange should be com pleted not later than autumn 1993.

SIGRID analysis

Prof.A.V.Bushuev, AARI, discussed the SIGRID Format and suggestions for its modification. The group recommended including tables 1,2,4,5 and 14,15 from SIGRID Format in a short version, which corresponds to the modern requirements of World Climate Research Programme and measuring capabilities. The WDC-A representatives proposed adding tables related to the temperature and albedo of the ice surface. The participants agreed that these proposals should be developed at WDC-A and sent to Prof. A.V. Bushuev by October 1992. Roger Barry reported on the organization and activities of WDC-A for Glaciology. Vince Troisi gave a presentation on the activities of the EOS Data and Information System and the Snow and Ice Distributed Active Archive Center. Participants agreed to hold the next annual meeting in Washington D.C. in autumn 1993.


Roger Barry, Richard Armstrong and University of Colorado graduate student, Dan Bedford, visited the Institute of Geography of the National Academy of Sciences, Moscow, Russia (7-17 July 1992) as part of a collaborative project on cryospheric indicators of global change. A plan was developed to digitize and transfer to WDC-A selected snow cover and glacier data sets which are considered significant to the study of global climate change and will serve as validation data for remote sensing. The extensive snow cover data sets represent a range of spatial resolutions from relatively high density measurements over a small area (e.g., the Valdai Research Station north of Moscow) to the 3000 to 5000 stations of the Hydrometeorological Service which are spread throughout the former USSR. Most of the data are currently only available in hard copy form and therefore are being digitized both at WDC-A and at the Geographical Institute in Moscow. The transfer of these data to WDC-A as well as the necessary digitization and formatting will be an ongoing process over at least the next year. Details on the content of these data sets as well as updates on the archive status and availability of the data will be published in future NSIDC Notes.

One data set of primary interest to remote sensing com prises measurements of snow depth, density, and snow structure at approximately 200 m intervals along transects that are typically 1.0 to 2.0 km in length. These data repre sent uniquely valuable information for the validation of passive microwave snow cover retrieval algorithms where the transects provide a resolution between conventional point measurements and the large area integration of the passive microwave footprint.

Armstrong and Bedford also visited Dzankhuat Glacier and the University of Moscow Mountain Research Station located in Terskol (Caucasus Mountains). Armstrong met with the Director A. Oleynikov, to discuss a technology transfer program to provide improved avalanche forecasting for the Terskol area based on techniques recently developed in the United States and Switzerland. The Terskol and adjacent Mt. Elbrus area represents one the most active winter recreation sites in the former USSR.

The activities described above are supported by NSF Grant No. SES-9112420 (Geography Program and Division of International Programs).

For more information, contact: Richard Armstrong at: (303) 492-1828 or Internet:


DMSP Digital Data Archive

NSIDC and the National Geophysical Data Center (NGDC) are involved in a joint project to archive digital data collected by USAF DMSP satellites and copied to 8 mm tapes by Air Force Global Weather Central. This effort will make the complete DMSP data stream available for the first time. While the national archive for DMSP data will officially be at NGDC, NSIDC will provide user services to cryospheric and climate researchers for data collected by the Operational Linescan System (OLS) sensor (visible and infrared), SSM/I passive microwave data, SSM/T and SSM/T-2 temperature and water vapor sounders.

Funding for the program is being provided by NOAA, NASA and the Department of Defense. NSIDC's involvement is a result of our past activities with the analog DMSP/OLS collection and SSM/I sea ice concentration products.

While tape recorder problems have so far prevented continuous production of archive tapes, NGDC and NSIDC have made good progress in system design, software development and hardware procurement. In the next few months we will form a scientific advisory committee, composed primarily of members of the user community, which will meet on a regular basis to provide guidance. We also will convene a users conference in 1993.

For more information, contact: Greg Scharfen at (303) 492-6197 or Internet: or Herb Kroehl (NGDC) at (303) 497-6121.


SSM/I Sea Ice Concentration Grids

Special Sensor Microwave/Imager (SSM/I) Sea Ice Concentration Grids for the Polar Regions, Volume 1, rev. 1, 9 July 1987 - 31 December 1989, has been distributed. This revised CD-ROM contains corrected data for the following subdirectories:


All data files on this revision utilize the Hierarchical Data Format (HDF). NASA EOSDIS Project has determined that all Version 0 data sets will be distributed using this format.

Hierarchical Data Format (HDF) Structure

HDF was developed at the National Center for Supercomputing Applications (NCSA) to facilitate the exchange of data. Tools to read and manipulate this format on all platform types are in the public domain and are available via anonymous FTP. (See DMSP SSM/I Brightness Temperature and Sea Ice Concentration Grids for Polar Regions on CD-ROM-User's Guide, p. H-22--H24, for instructions.) IMDISP, Version 7.79, distributed with the SSM/I Sea Ice Concentration Grids, Vol. 1, rev.1, reads HDF data.

For those wishing to access the HDF ice concentration grids using other analysis or display tools, the following tables indicate the offset resulting from adding HDF objects to the SSM/I sea ice concentration grids. Note that the grids (data) begin at the 203rd byte, (i.e., offset 202 bytes).

For further information, contact NSIDC User Services.

Table 1. HDF structure for the SSM/I sea ice concentration grids for the Northern Hemisphere

File Header04
DD Block and Pointers4198
Raster Image202136192
Image Palette135394768
Number type1371624
Image Dimensions13716620
Image Dimensions-81371864
Raster Image Group13719012

Table 2. HDF structure for the SSM/I sea ice concentration grids for the Southern Hemisphere

File Header04
DD Block and Pointers4198
Raster Image202104912
Image Palette105114768
Number type1058824
Image Dimensions10588620
Image Dimensions-81059064

Landmasks for SSMR and SSM/I

The landmasks and coastline overlay grids provided for use with the SSM/I and SMMR brightness temperature grids distributed by NSIDC on CD-ROM are not identical. This is because the overlays were developed in two different environ ments.

The SSM/I overlays developed at NSIDC in 1985 used the CIA World Data Base I (WDB-I) coastlines, packaged with the NASA Ocean Data System (NODS) which was developed by the Jet Propulsion Laboratory and transferred to NSIDC as the Cryospheric Data Management System (CDMS), for processing the SSM/I grids.

The SMMR landmask, developed at NASA/GSFC, used the CIA World Data Base II (WDB-II) which had a finer grid than WDB-I. Also, NASA/GSFC used a rather complicated method for assigning mixed land/ocean pixels that is different from the JPL/NSIDC procedure. A description of the NASA/GSFC process is contained in the forthcoming SMMR Atlas (Gloersen, 1992).

These differences result in about a 3% difference in the number of ocean pixels on the North Polar grid. This difference was brought to our attention by one of the SMMR CD-ROM product users.

It was also learned that the SMMR South Polar landmask size is 317 x 332 pixels, instead of 316 x 332 pixels. The difference in size results from the neglect to remove the carriage return-linefeed combination in each row of the mask that is hidden in image files created in a DEC VAX VMS environment. This requires that the original mask be "trimmed" by one pixel (two bytes) on the right-hand edge, a task easily handled by any matrix-based language such as IDL.

For convenience, NSIDC has prepared a diskette containing the North and South Polar landmasks from WDB-I and WDB-II, including a corrected South Polar mask based on WDB-II. This PC-compatible diskette is available on request from NSIDC. Ask for the "Passive Microwave Landmasks" diskette; please specify 5.25" or 3.5" size.

To facilitate intercomparison of SSM/I and SMMR data, it is suggested that you select either the WDB-I or WDB-II landmask for your work, and use that selection exclusively. Otherwise, your intercomparisons may lead to inconsistent results.

Reference: Gloersen, P., W. J. Campbell, D. J. Cavalieri, J. C. Comiso, C. L. Parkinson, and H. J. Zwally. 1992. Arctic and Antarctic sea ice, 1978-1987: Satellite passive microwave observations. National Aeronautics and Space Administration, Special Publication 511: pp. 290.

For more information, contact NSIDC User Services.


ARCSS OAII Modelling Workshop

On 13-14 July, Claire Hanson attended the Arctic System Science (ARCSS) Ocean-Air-Ice Interactions (OAII) Modelling Workshop, held at the Hopkins Marine Biological Station of Stanford University, in Monterey, CA. The 35 or so attendees discussed progress and problems in modelling Arctic ocean-related processes. NSIDC is funded by NSF to provide data management services for ARCSS/ OAII, and is working with these investigators to facilitate their access to data needed for their ARCSS projects. To this end, we proposed the production of a "model test data kit," a CD-ROM containing one year of data covering Arctic regions, from many different data sets, to be used in developing, testing, and validating ocean- and ice-related models. The suggestion seemed favorably received, and NSIDC will poll the group to determine which data sets are preferred for inclusion.


New Sea Ice CD-ROM Planned

NSIDC has begun the design of a new CD-ROM product, targeted for completion by the end of 1992. Weekly sea ice data from the Navy - NOAA Joint Ice Center (Arctic 1972-1991, Antarctic 1973-1991), archived in the WMO SIGRID (sea ice grid) format, will be provided on CD-ROM with software tools to select and output data by time and location. Additional software may be developed to facilitate gridding the data into a user-selected projection.

The NSIDC product will be designed to be usable in different computing environments, ideally on PC, Macintosh, VAX, and Unix workstations. An annual update mechanism will be developed. The cost of this product has not yet been determined, but we hope to be able to keep it under $100.

If you have comments or would like more information on this plan, or you would like to be placed on the list of potential "beta testers," contact NSIDC User Services.

1991 Sea Ice Data Received

One reel of 9-track tape is now available with the Navy - NOAA Joint Ice Center weekly sea ice data for 1991 (Arctic East, Arctic West, Antarctic). These data are in the SIGRID format, and will be included on the planned CD-ROM product. However, for those who wish to use the 1991 data right away, the tape is available immediately. Cost is $115 plus $15 shipping/handling for U.S. orders, or $20 shipping/handling for orders shipped outside the U.S.


Seasonal Sea Ice Monitoring and Modelling Site

During May - June 1992, M. Serreze, J. Maslanik, J. Key, and A. Schweiger participated in a field program in conjunction with the Seasonal Sea Ice Monitoring and Modeling Site (SIMMS) effort near Resolute Bay, NWT. This ongoing Canadian program (1992 representing Year 3 of a 5-year program), managed by Dr. Ellsworth LeDrew of the University of Waterloo, emphasizes collection of data sets for validation of sea ice characteristics derived from Earth Resources Satellite (ERS-1) synthetic aperture radar (SAR) imagery and for use in graduate student theses projects on the Arctic surface energy budget. Data were collected at a "home" site near the shore of Griffith Island, approximately 20 km south-southwest of Resolute Bay, Cornwallis Island, NWT, at an instrumented "first-year ice" site in the passage between Cornwallis and Griffith islands, and at a "multiyear ice" site on a multiyear floe in Wellington Channel between Cornwallis and Devon islands. The main contribution of the CIRES, University of Colorado group was to help extend the SIMMS measurements to include observations on a multiyear ice floe, to collect specific data useful for energy budget calculations applicable for ice modeling, and to measure surface albedos, skin temperatures, ice and snow pack temperatures, and snow depths over a relatively large area for comparison to satellite imagery. Plans are underway to participate in the spring 1993 SIMMS program.

For information, contact: James Maslanik at (303) 492-7221 or Internet:


Snow and Ice Publications

Barry, R.G., Armstrong, R.L. and Maslanik, J.A. (1992) Snow cover conditions in European Russia and Georgia: a comparison of station data and passive microwave-derived values. Abstracts, Association of American Geographers 88th Annual Meeting, San Diego, Association of American Geographers, Washington, DC, p.13-14.

Barry, R.G. (1992) The significance of global snow and ice for global change studies. Geojournal, 27, p.293-297.

Barry, R.G. (contributor) (1992) Observed climate variability and change. (ed. C.K. Folland, et al.). (In: J.T. Houghton, B.A. Callendar and S.K. Varney, Climate Change 1992: The Supplementary Report to the IPCC Scientific Assessment, Intergovernmental Panel on Climate Change, WMO/UNEP, Cambridge University Press, Cambridge, p.137-170.)

Barry, R.G., Key, J., McLaren, A.S., Miles, M.W., Schnell, R.C. and Serreze, M.C. (1992) Arctic Ocean-atmosphere-ice system studies (Final Summary Report). (In: Ocean Technology 1991 Program OCNR 112192-8, Office of Naval Research, Arlington, VA, p.127-146.)

McLaren, A.S., Walsh, J.E., Bourke, R.H., Weaver, R.L. and Wittman, W. (1992) Variability in sea-ice thickness over the North Pole from 1977 to 1990. Nature, 358, p.224-226.

*Bold names are individuals at WDC/NSIDC.