In this Issue



Issue 5, Spring 1993


Polar DAAC User Group Meeting

The Fourth Polar DAAC (Distributed Active Archive Centers) User Group (PoDAG) Meeting was held in Seattle, Washington, on the 27 and 28th of April. This brief report outlines the discussions held and the actions taken which are of interest to the wider cryospheric user community. Please contact R. Weaver at NSIDC, T. George at ASF, or K. Steffen at University of Colorado (PoDAG Chairman) for further information on any of these items.

Those attending the meeting included representatives from the Alaska SAR Facility Distributed Active Archive Center (DAAC), Fairbanks, the National Snow and Ice Data Center DAAC, Boulder, Colorado, the members of the PoDAG, NASA Headquarters, Earth Science Data and Information Systems (ESDIS) and Hughes Information Systems. PoDAG members are selected from the snow and ice research community, each to represent a specific research area. They are appointed by D. Butler, NASA Headquarters.

The most important work of PoDAG is advising the DAACs on science driven data priorities. This information directly affects the data set development goals of each DAAC. To this end, the PoDAG spent a great deal of time developing specific lists of parameters needed to conduct EOS-focused snow, ice and land research. PoDAG agreed that tables of parameters and the related measurement systems are of little use unless they are focused on specific scientific goals. PoDAG agreed that they would list data/parameter needs which fit one of two criteria: those needed for global climate model boundary conditions or validation; those needed to determine surface energy fluxes to an accuracy appropriate for detection of a C02 doubling signal. These criteria are somewhat arbitrary and can be changed or augmented, but the PoDAG thought that such a target is necessary in order make such parameter/measurement tables relevant.

The tables are still in draft form. However, if you are interested in further information, please contact either DAAC or the PoDAG chairman.

From Headquarters and ESDIS Project

Dr. R. Thomas (NASA-HQ) described the recent reorganization of the EOS program management and an upcoming NASA Earth Science research program review (held 15-16 June). Dr. Thomas stressed the need to explain the role of the cryosphere in the global climate system and how the specific work (data systems and basic research) undertaken with NASA sponsorship has advanced our understanding of this interaction.

Mr. Greg Hunolt, ESDIS V0 Project Manager, discussed recent progress in the EOSDIS Version 0 effort. ESDIS is gearing up for the operational phase of the Version 0 system scheduled for July 1994, and the development of the EOS Core System (ECS) by the Hughes Information Systems contract team. Hunolt stated that the migration of data from the Version 0 system to Version 1 will be driven by the science priorities.

From Alaska SAR Facility DAAC

Dr. Willy Weeks reported on ASF activities. There are currently 128 active projects which are authorized to receive SAR data from ERS-1 and J-ERS-1, with 5 new projects pending approval. Sea ice research is the largest group, but more land-related users are requesting data. The large volume of data collection from these satellites has caused severe computer system and operations staff overload. ASF has modified its processing profile to process only data on user demand in order to expedite the flow of data to users. J-ERS-1 data are now available to NASA-approved users via ASF. ASF is developing a CD-ROM containing SAR data which illustrates the multiple uses of these data. ASF is losing both its Chief Scientist (W. Weeks) and Operations Director (J.Miller) who are retiring. They are actively recruiting for these positions.


Dr. Roger Barry reported on the status of NSIDC DAAC activities. Processing details are on p. 4.

Dr. Ted Scambos, NSIDC DAAC, presented plans for the AVHRR 1 km snow and ice subset, to be developed at NSIDC. These data requirements are derived by user needs for cloud detection/type/fraction, ice surface temperature, and basin-wide ice motion information. See p. 4 for detailed information.

He also reported on the availability of satellite altimetry data over ice sheets through NSIDC. These data are currently stored on a system operated by Dr. J. Zwally, GSFC. NSIDC will investigate, at PoDAG and NASA HQ request, transfer of these data to the NSIDC Data Archive and Distribution System (DADS) in the near future.

The EASE (Equal Area SSM/I) grid was proposed as a replacement for the SSM/I Polar Stereographic Grid. PoDAG deferred action until NSIDC provides additional grid intercomparison test results and demonstrates re-mapping tools to convert EASE-Grid data to the SSM/I Polar Stereographic Grid.

Other Items of Interest

Dr. Drew Rothrock (Applied Physics Lab, U. Washington) reported the successful negotiation of access to TOVS data (4-87 to 11-88) from the NASA TOVS Pathfinder group. Currently these data will be only available to the POLES Interdisciplinary Project, with higher level products generated by POLES archived at NSIDC. The PoDAG recommended that a common TOVS-AVHRR data set be developed by NSIDC as these data become available.

NSIDC and POLES will collaborate on an effort to improve accessibility to TOVS data and products to snow and ice scientists. This will include preparation of a users guide to the products and data sets.

Brief reports were given on recent meetings. The SAR Geophysical Processor System (GPS) users group met 16-17 March. They have formed three validation teams: ice motion, ice classification, and waveform products. These teams have each written an evaluation report (available from ASF User Services).

A group met at the Byrd Polar Science Center, OSU, Columbus, to discuss a RADARSAT Antarctic Mosaic. This effort plans to acquire SAR data from RADARSAT for a high resolution map consisting of about 500 SAR scenes of 100 x 100 km size. The proposed acquisition period is October 1996.

The next PoDAG meeting is tentatively scheduled for November 1993 at the Alaska SAR Facility, Fairbanks.

A RADARSAT GPS Planning Meeting will be held in fall 1993 to review candidate R-GPS products. A committee was set up (D. Rothrock, chair) to schedule this meeting.

An Alaska SAR Facility Users Meeting is to be held at the Battelle Seattle Science Center, July 27-29, 1993. Results of ERS-1 investigations using ASF-collected data will be presented in both invited papers and extended poster sessions. Contact: Dr. Drew Rothrock, APL, University of Washington or (D.ROTHROCK/OMNET).


Model Test Kit for Arctic Research

An Arctic model analysis test kit is being compiled at NSIDC for distribution on CD-ROM to ARCSS investigators. The test kit will consist of a group of data sets over the Arctic that coincide chronologically and will include information on the climate, land and sea ice, ocean, soils, atmospheric chemistry, and topography (both land and ocean). The data will be in a gridded form (as yet unspecified), with the possibility of including the original (non-gridded) data for specific modeling needs. This collection of data will be useful to compare model outputs of the Arctic region to determine their accuracy.

The list of specific data sets to be included in the model test kit has been through an internal review at NSIDC, and was presented at the recent meeting of the ARCSS Executive Committee by Dr. John E. Walsh, ARCSS Investigator at the University of Illinois. The response was favorable and full support has been given to NSIDC to pursue this project.

We expect the ARCSS Executive Committee will soon constitute an ARCSS Modeling Working Group to advise on and coordinate matters relating to data modeling issues in ARCSS-funded research. NSIDC will ask the Working Group to review the model test kit plan and provide advice on the content of the CD-ROM.

If you would like to contribute ideas to the project, especially thoughts on possible data sets, gridding schemes, or a timeframe for the data availability, please contact NSIDC User Services.


SSM/I CD-ROM Distribution Schedule

CD-ROM volume 16, containing SSM/I brightness temperature grids for April-June 1991, was distributed to NSIDC's mailing list of 360 subscribers during the week of 14 June. Volumes 17-18, containing data for July - December 1991, are now at the CD-ROM mastering facility; the expected distribution is 15 July. Volume 18 marks the end of the gridded brightness temperature data from DMSP satellite platform F8. NSIDC has begun to process SSM/I data from platform F11, launched in November 1991 with usable data beginning in December 1991. Additional SSM/I brightness temperature CD-ROMs will be produced and distributed by NSIDC; further details will be announced in the next issue of NSIDC Notes.

SSM/I derived sea ice concentration grids for 9 July 1987 - 31 December 1989, on one CD-ROM, were distributed in January 1992. The second volume in this series is completed and scheduled for distribution in late July 1993. This second volume will contain sea ice concentration grids for 1 January 1990 - 31 December 1992, the end of the DMSP satellite platform F8 time series. Sea ice concentration from DMSP platform F11 SSM/I data will be produced and distributed on CD-ROM in the future.

SSM/I CD-ROM Error Notes

NSIDC has compiled a complete log of SSM/I brightness temperature and sea ice concentration CD-ROM processing and mastering errors. This list was distributed with CD-ROM volume 16, and will also be incorporated in the DMSP SSM/I Brightness Temperature and Sea Ice Concentration Grids for the Polar Regions User's Guide. A new version of this User's Guide will be distributed with the SSM/I ice concentration CD-ROM volume 2, in late July 1993.


Standard Data Formats

Point data are made up of records and fields that describe specific scientific phenomena at some location. The Point Data Working Group (PDWG) is a sub group of the ESDIS Standard Data Formats Working Group. The PDWG, a collaborative effort of the National Geophysical Data Center (NGDC), NSIDC and the National Center for Supercomputing Applications (NCSA), has been formed to address issues regarding implementing point data in HDF. Currently the HDF software does not handle point data.

There are two steps involved in this task: 1) organizing the data into HDF files, and 2) creating the tools to read such files.

  1. An HDF Vset is a logical grouping of diverse, but related data items within an HDF file. HDF Vsets contain two types of storage elements: Vgroups and Vdatas. A Vdata may only contain data, while a Vgroup contains references to Vdatas or other Vgroups. The Vset, Vgroup and Vdata can be hierarchically organized and linked. This data structure has been proposed as the method in which to store point data. The data in a Vdata is organized into fields. A field can be represented by an integer (8, 16 or 32 bits signed and unsigned), character (represented by 8 bits unsigned) and/or floats (32 or 64 bits). Ted Habermann (NOAA/NGDC) has created a general application for translating data into such a structure and applied it to NSIDC's Historical Arctic Rawinsonde Archive as a test.
  2. This step involves the development of a set of HDF data access and manipulation utilities for use with point data.

The HDF library does provide a tool called Vshow, but it has limited functionality. Vshow is primarily used to examine the contents of Vsets. Vshow is also useful for converting Vsets in HDF files into ASCII.

For information regarding the Point Data Working Group, please contact NSIDC User Services.

For information regarding HDF Vset, contact the National Center for Supercomputing Applications at 217-244-8524 or


Field Investigations

During 1 May - 15 June 1993, investigators from the University of Colorado collected energy budget and sea ice data in cooperation with Canadian researchers as part of the Sea Ice Monitoring and Modeling Site (SIMMS) experiment near Resolute Bay, NWT. Objectives of the University of Colorado effort are to validate retrieval algorithms for AVHRR and ERS-1 ATSR imagery (surface temperature, cloud properties, albedo) and SSM/I data (temperature, weather effects, and surface properties), and to refine energy exchange parameterizations in sea-ice modeling. Operating from a camp situated on first-year fast ice, the C.U. researchers collected skin temperatures, albedo, and other surface measurements in conjunction with AVHRR overpasses, carried out detailed surveys of surface topography and hummock/meltpond ratio on a multiyear ice floe situated near the camp, and assisted in measuring energy balance components at meteorological stations established on first-year and multiyear ice. C.U. researchers participating in the program for 1993 are J. Maslanik, M. Serreze, J. Key, and J. Heinrichs. The ongoing SIMMS experiment is directed by Ellsworth LeDrew, University of Waterloo.

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

1-km Polar AVHRR Archive: Progress Report

NSIDC has begun work on creating a bi-polar 1-km AVHRR image data archive, comprised of a polar subset of the Global Land 1-km AVHRR Data Set, currently collected by the Eros Data Center (EDC), and Antarctic 1-km HRPT AVHRR data from the Antarctic Remote Sensing Center at Scripps Oceanographic Institute. The effort is in response to satellite data requirements from our DAAC Advisory Group, and to numerous requests from the user community at large. For some time, NSIDC has perceived a strong interest in the polar science community in using 1-km AVHRR data to derive several important polar geophysical properties, and for mapping and monitoring the polar ice caps in general. AVHRR has a broad range of proven and potential applications to polar science, including sea-ice concentration mapping, sea-ice motion mapping, measurement of ice surface temperature, ice shelf extent monitoring, and glaciological feature- mapping on land ice sheets. Pending funding approval/award EROS Data Center and Scripps will begin sending NSIDC their polar 1-km AVHRR data. Combined, these two data sets will provide nearly complete coverage of bipolar sea ice, land ice, and polar lands. This data set can be merged with the microwave and ancillary data sets to create synoptic views of polar climatic and hydrologic systems. The archive will contain data starting from April 1, 1992 (for the Antarctic HRPT stations) through 1993, and there is strong intent to extend the data collection through 1994 and perhaps beyond. We have requested funding for data ingest and initial processing beginning August 1 of this year. If startup funding is granted NSIDC would begin responding to user requests in October 1993. The data are intended for use by the snow and ice science community, to address problems in snow and ice science and related aspects of climatology and oceanography. Users wishing to look at high-latitude land areas for objectives concerning geospheric or biospheric questions will be referred to the Global Land 1-km AVHRR Data Set available at Eros Data Center.

Response to the announcement, in the Spring edition of NSIDC Notes, that a comprehensive AVHRR data set for the poles may be assembled by NSIDC, has been positive. Letters or e-mail from 15 potential users have asked to be kept informed of progress; an additional 3 e-mail notes were from institutions managing other HRPT stations collecting polar data suggesting that NSIDC incorporate their data into the overall archive. This may be pursued at a later date. Our Polar DAAC Advisory Group, comprised of members of the polar science community and including several likely users of the data, has been very supportive of these activities.

For more information contact: Ted Scambos at (303) 492-1113 or Internet:


Permafrost Bibliography Update, 1988-1992

Glaciological Data, Report GD-26 is available. This publication was prepared in conjunction with the Sixth International Conference on Permafrost to be held in Beijing, July 1993. The bibliography, which updates those published in GD-14 and GD-21, contains over 3,000 citations covering all aspects of permafrost research. Copies are available, either paper or diskette, for $10.00

Contact NSIDC User Services at (303) 492-5171 or

GD-25 is still in progress. This report is a joint project of the Earth-Observations Laboratory at the University of Waterloo and WDC-A for Glaciology. We expect publication later this summer.