In this Issue
PRODUCTS AND SERVICES
DEFENSE METEOROLOGICAL SATELLITE PROGRAM (DMSP) UPDATES
ARCTIC SYSTEM SCIENCE (ARCSS)
A research team led by investigators from the University of Washington, St. Olaf College, and NSIDC visited a region of the Antarctic ice sheet where several important past events appear to be preserved in the ice. The region is known as Siple Dome, a 120 kilometer wide gentle dome of ice located on the boundary between the West Antarctic Ice Sheet and the Ross Ice Shelf (81.5 degrees S, 150 degrees W). Satellite imagery of the region (including Landsat, SPOT, and the NSIDC archive of polar 1-km AVHRR data) reveals several faint scars and undulations in the ice surface northeast of the dome summit, as well as a remarkable view of the dome itself. Please note that the graphic of the Siple Dome area (Figure 1) that appeared in the original hard copy version of NSIDC Notes, Vol. 13, is unavaible at this time. We hope to have this graphic added here in the future. Researchers have speculated that the northeast region might represent an ancient ice stream (a large drainage glacier for the ice sheet) that has ceased rapid motion. Others have proposed that Siple Dome itself may be a remnant from the last ice age when Antarctica had a much more extensive, thicker, ice sheet. Both ideas are being tested by the current field work.
The camp for this field work was located about 3 km southeast of the summit, based on an initial examination of the AVHRR data. Camp consisted of two 12 feet x 16 feet huts and three two-man tents, five snowmobiles, just over one ton of food, and 800 gallons of fuel, all placed there from McMurdo Station via C-130 aircraft in mid-November of 1994. Temperatures were balmy by Antarctic standards, ranging from a low of -21 degrees C to just above zero degrees C on the last day of work (15 December 1994). The team immediately began the field work, setting up a grid array of steel marker poles over a 10 km x 10 km area covering the summit, and conducting radar profiles of the ice layers below the surface using a sled-based radar. Radar surveys extended up to 75 km away from camp, covering many of the features shown in Figure 1. The location of the marker poles and the precise topography of the dome was determined to within ± 2 cm using high-precision Global Positioning System (GPS) receivers and standard optical surveying techniques.
Fig. 1. Siple Dome as imaged by the AVHRR sensor. North is up, and illumination is from the lower left. White lines on the image mark the locations of radar and GPS traverses. Note the curvilinear scar feature northeast of the dome; this was determined by the recent field work to be an ancient shear margin of a now-dead ice stream.
Both data sets are being used to determine the history and current status of Siple Dome and, by extension, this portion of the Antarctic ice sheet. GPS data analysis, however, will have to await a second visit to the area, planned for late 1996, to measure the motion of the grid of poles. Initial analysis of the radar profiles has confirmed the idea that there is an additional 'dead' ice stream northeast of Siple Dome. This discovery implies that the configuration of the drainage of the ice in this part of Antarctica can change with time, which has important consequences for models of the evolution of the ice sheet during climate change. Radar profiles also suggest that the current summit has probably been located in more or less the same place for about 10,000 years, but may have been subsumed into a larger late Pleistocene Antarctic ice sheet prior to that time. The isolation of the Siple Dome feature from the rest of the Antarctic ice sheet could be a result of the development of the ice stream system surrounding it, which drained off the ice and left it as a local high. This scenario supports a hypothesis that this portion of the Antarctic ice is shrinking rapidly, and that the mechanism for that shrinking is mass flux through the ice streams.
For further information please contact: Ted Scambos at Internet: email@example.com, or National Snow and Ice Data Center, CIRES, Campus Box 449, University of Colorado, Boulder, CO 80309-0449 USA, or +1 303.492.1113 (phone), or +1 303.492.2468 (fax).
Northern Hemisphere Combined Snow Cover and Sea Ice Extent - NEW PRODUCT
NSIDC has developed a northern hemisphere cryospheric product which combines snow cover and sea ice extent at weekly intervals for the period 1978 to 1994. The data set will also include monthly climatologies describing snow and sea ice extent in terms of average conditions, probability of occurrance, and variance. Funding for this project has been provided by the NOAA Climate and Global Change Program. This product will be available in an azimuthal equal area (25 km) projection using the NSIDC Equal Area SSM/I Earth (EASE) Grid.
The snow cover extent is based on the digital NOAA-NESDIS weekly northern hemisphere snow charts, revised by D. Robinson (Rutgers University) and re-gridded to the EASE-Grid. The original NOAA-NESDIS weekly snow charts are derived from the manual interpretation of AVHRR, GOES and other visible-band satellite data. The sea ice extent is based on the existing NSIDC polar-stereographic, sea ice concentration grids. The NSIDC sea ice concentrations are derived from the SMMR and SSM/I passive microwave brightness temperature data. The period of time covered represents the SMMR-SSM/I era (1978-present). This combined snow cover and sea ice data set will be available for distribution from NSIDC on CD-ROM in late 1995.
For further information, contact Richard Armstrong at Internet: firstname.lastname@example.org or (303) 492-1828 (phone), or (303) 492-2468 (fax).
NSIDC announces the availability of the TOVS Pathfinder Path-P Gridded Daily Arctic Atmospheric Data (1 April 1987-30 November 1988). The data set was produced by Dr. Jennifer Francis (Rutgers University) and Dr. Axel Schweiger (University of Washington Polar Science Center) as part of the NASA EOS interdisciplinary science investigation, Polar Exchange at the Sea Surface (POLES), in coordination with the NOAA/NASA Pathfinder Program. The data set was developed to address the particular needs of the polar climate research community. The Path-P data set contains the level-3 atmospheric parameters, shown in the table below, over the Arctic region poleward of 60 degrees N. The parameters areretrieved from the TIROS-N Operational Vertical Sounder System (TOVS) High-resolution Infrared RadiationSounder (HIRS) and the Microwave Sounding Unit (MSU) sensors by using the physical-statistical retrieval method of Chedin, et al. (J. Clim. Appl. Met., 24: 128-143, 1985). The retrieval method has been improved for use in sea-ice-covered areas (Francis, JGR, 99(D5): 10,395-10,408, 1994).
Table 1. Estimated Accuracy of Path-P Level 3 Parameters
|Parameter||Description||Units||Estimated Accuracy (rms)|
|TEMP||Level temperatures at 50, 70, 100, 300, 500, 600, 700, 850||K||3K|
|WVAPOR||Layer Precipitable water bounded by 300-400, 400-500, 500-700,
700-850, 850-1000 mm
|SKTEMP||Surface Skin Temperature||K||3K|
|FCLD||Effective Cloud Fraction||%||0.3|
|EMISS||Surface Emissivity (50 Ghz)||- - -||5%|
|PBLSTRAT||Boundary Layer Stratification||K||5K|
|Cg||Geostrophic drag coefficient||- - -||30%|
To faciliate the combined use with other data sets, TOVS Path-P data are available on a 100 km version of the Equal Area SSM/I Earth (EASE) grid, an emerging standard used for a number of polar data products generated and archived by NSIDC. Path-P data products are implemented in the National Center for Supercomputing Applications (NCSA) Hierarchical Data Format (HDF) and follow standards and recommendations developed for the EOSDIS Version 0. For users unfamiliar with HDF, examples of access software are provided with the TOVS data set. A comprehensive description of this data set is provided in the document "TOVS Pathfinder Path-P: Gridded Daily and Monthly Arctic Atmospheric Data from TOVS."
The Path-P data files, User's Guide, and sample access software are staged on the NSIDC ftp server and are located in the anonymous ftp directory /pub/DATA_SETS/DATA/TOVS on the host sidads.colorado.edu. The data are also advertised through the EOSDIS Version 0 IMS system (telnet: eosims.colorado.edu 12345) which supports the visualization of browse products generated from the 850 mb temperatures retrieved from the daily products (a gray-scale example is shown in Figure 2). Please note that a color version of the black and white version of the graphic Temp 850 mb (Figure 2) may be added here in the future.
DMSP F11 SSM/I Monthly Averaged Sea Ice Concentration grids, generated using the NASA Team algorithm, are now available. The data set is a continuation of the DMSP F8 SSM/I Monthly Averaged Sea Ice Concentration grid product.
To obtain F11 monthly averaged sea ice concentration data from NSIDC: ftp sidads.colorado.edu, (login as 'anonymous'), (type your e-mail address as password), cd pub/DATA-SETS/DATA/SSMI/F11.
The F11 ice concentration data are in HDF (Hierarchical Data Format). Software to read and manipulate HDF data files as well as help in using the software is available from The HDF Group. IDL and other commercial and "shareware" packages can also be used to read and manipulate HDF files.
DMSP-F13 satellite was launched from Vandenberg Air Force Base on 24 March 1995. The F13 satellite has a 17:40 (approximate) local ascending node time. NSIDC plans to process this data as soon as it becomes available.
With the launch of the F13 satellite, and because of data recording device problems, data processing of the F11 data stream at Fleet Numerical Operations Center has been de-prioritized. This means that not all available F11 data are being processed. This may result in data gaps beginning with the April 1995 data products.
Software to visualize data in Hierarchical Data Format (HDF) is available from The HDF Group. Information about the software and about HDF is provided on several World Wide Web sites. Below we reprint, with thanks, NCSA's WWW text describing NCSA Collage for MS Windows version 1.2 BETA 1, to help familiarize users of NSIDC's DMSP F8 SSM/I ice concentration data and DMSP F11 SSM/I brightness temperature and ice concentration data. We urge you to explore the WWW URLs listed for more detailed information and access to the software itself. Thanks also to S.J.S. Khalsa, ECS Science Liaison Interface Manager, for digging out this information for us.
Welcome to the second beta release of NCSA Collage for Microsoft Windows. Collage is a collaborative visualization program, allowing the user to collaborate and share data across the three supported platforms: X-Windows workstations, Apple Macintosh systems, and finally, Microsoft Windows 3.x systems. The data sharing is done via a TCP/IP network, utilizing NCSA's Data Transfer Mechanism (DTM), which is built on top of the Microsoft WinSock standard TCP/IP network socket library API.
Requirements for using Collage:
Running Collage as a Stand-alone Package:
If you do not want to use the networking capabilities of Collage, and don't have a WinSock-compatible network system on your PC, you can still use it as a standalone visualization package. Download the NULLSOCK.ZIP package from NCSA (or take it from the install disk) and unzip it. Place the WINSOCK.DLL in the same directory as your NCSA Collage executable. This will give you a "fake" network library.
Installing and Running Collage:
Read the RELEASE.WRI file for instructions on installing Collage, and the COLLAGE.WRI file for help on finding your way around Collage.
Send questions and bug reports to email@example.com
A discussion of the use of HDF within the Earth Observing System (EOS) Program is presented at: http://observer.gsfc.nasa.gov/ecs_news/winter/hdf.html.
Here is the URL for HDF viewers: http://www.ncsa. uiuc.edu/SDG/Software/Brochure/PCSoftDir.html. This is the site where you can choose PCShow (no longer supported) or Collage for MS Windows.
Here is how to obtain binaries for PCShow (no longer supported) or Collage for MS Windows, via ftp: ftp ftp.ncsa.uiuc.edu
cd /DOS = for PCShow
or cd /Windows/Collage = for Collage
Then cd to either /beta or /old depending on which version you wish to obtain.
NSIDC welcomes your comments regarding the HDF data products we distribute. Contact NSIDC User Services.
As many of you know, NSIDC plans to distribute cryospheric products from NASA's Earth Observing System (EOS). The NSIDC DAAC wishes to bring to your attention several important issues regarding cryospheric products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) missions, based on discussions at recent Instrument Team meetings.
There are currently four products planned from MODIS data that are directly relevant to the snow and ice community: daily snowcover (in Level 2 and Level 3 formats), gridded weekly snowcover, daily sea ice maximum extent (in Level 2 and Level 3 formats), and gridded weekly sea ice cover. These products are being developed by V. Salomonson, D. Hall and G. Riggs at NASA. Algorithm Theoretical Basis Documents (ATBDs) are available for each of the products via WWW at URL:http://spso.gsfc.nasa.gov/atbd/pg1.html.
The currently planned MODIS snow and ice products do not fully utilize the capability of the sensor. The spectral resolution and spatial/temporal coverage make MODIS suitable for a number of other cryospheric products as noted below.
The proposed EOSDIS gridding scheme is inconvenient for depicting snow and ice in the polar regions and questions remain as to whether the integrity of the data may be at risk in any re-gridding. Current plans call for the Level 3 (gridded) products to be produced and archived in the International Satellite Cloud Climatology Project (ISCCP) sinusoidal grid which is being adopted as the official EOSDIS grid for Level 3 products. [Rossow, W.B. and Garder, L. (1984) Selection of a map grid for data analysis and archival. Journal of Climate and Applied Meteorology, 23: 253-1257. World Climate Research Programme. (1988) International Satellite Cloud Climatology Project Documentation of Cloud Data. WMO-TD-No.266.]
NSIDC will archive the official MODIS products, but could also implement other algorithms to generate products from the MODIS data. NSIDC would like input from the snow and ice community on the usefulness and applicability of MODIS data for other products (such as ice surface temperature, ice motion, polar regions albedo) and specific user needs.
NSIDC could also implement MODIS products in other projections and grids. Candidates are a polar stereographic projection and an azimuthal equal area projection (using the EASE-Grid scheme employed in current DMSP SSM/I data products distributed by NSIDC). NSIDC would like comments from the snow and ice community on the usefulness of the ISCCP grid for polar regions research, whether it satisfies their requirements, and the usefulness of the two proposed alternatives.
The primary contribution that ASTER data can make to cryospheric problems is glacier monitoring, building on similar work with LANDSAT and SPOT data. The usefulness of ASTER data for glacier research is being explored by H. Kieffer and J. Kargel at the USGS (Flagstaff, Arizona). There are several research opportunities in this area: spectral discrimination of snow, ice and rock using ASTER bands 3 (0.76-0.86 µm) and 9 (2.36-2.43 µm), same-pass stereo imaging of glaciers using band 3 and the short-wave infrared bands (SWIR) which are pointable, and the prospect of spatial/temporal coverage that could support yearly surveys of global glacier boundaries, displacement, surges, and ice shelf disintegration.
Products from ASTER relating to glaciers have been designated by NASA as non-standard products, consequently funding for their development is limited, and competition for scheduling data collection for glacier work that does not overlap with data collection for other ASTER products will be difficult. The status of glacier products from ASTER data could be improved if the user community supports implementation of specific applications and products. The EOS Science Implementation Plan will include a chapter outlining the proposed ASTER glacier work.
Call to the Cryospheric Community
NSIDC would like to serve as a discipline-specific interface for these products. We seek comment from glaciologists, hydrologists, and appropriate disciplinary organizations on:
Please send your comments to: Greg Scharfen, Remote Sensing Scientist, Campus Box 449, University of Colorado, Boulder, CO 80309-0449 or Internet: firstname.lastname@example.org.
Matthew Cross, ARCSS Data Coordinator at NSIDC, attended the fourth meeting of the Surface Heat Budget of the Arctic Ocean (SHEBA) Science Working Group on Wednesday, 31 May, in Baltimore, MD. Members of the SHEBA Science Working Group and SHEBA Principal Investigators were in attendance, as well as Dr. P. Webber and Dr. M. Ledbetter from NSF Office of Polar Programs, and Dr. L. Clark from NSF Directorate for Geosciences, Division of Ocean Sciences. The purpose of the meeting was to discuss the SHEBA Phase I projects that were recently funded, program budget issues, the SHEBA review process, field experiment planning, and program coordination. Matt gave an overview of the current activities at NSIDC for SHEBA data management, which include collecting and making accessible data sets necessary for SHEBA-related research. The proposed data management scheme for the period during and after the SHEBA field experiment was also discussed, emphasizing a proposed cooperative data management plan involving NSIDC and the UCAR Office of Field Project Support.
For further information, contact NSIDC User Services.
The results of a workshop to address permafrost data rescue and access are reported in Glaciological Data Report, GD-28, to be published in July by WDC-A for Glaciology. The workshop, held in Oslo, Norway, 3-5 November 1994, was supported by the NOAA-ESDIM programs, the NSF-ARCSS program and the International Permafrost Association (IPA) and convened by Dr. Roger G. Barry, Director, WDC-A for Glaciology/NSIDC and Chair of the IPA's Working Group on Permafrost Data and Information. There were 19 attendees from eight member countries of the IPA representing permafrost science and data management.
GD-28 reports on the priorities established for permafrost data according to their use for detecting global change, modeling, engineering design, process understanding and impact evaluation. An implementation plan developed for a Global Geocryological Database (GGD) with national or regional nodes is also described. Russian data at risk are targeted as a first priority and the report identifies critical data sets and next steps. GD-28 also includes an inventory of Russian maps of permafrost data and a list of major Russian organizations that hold permafrost data. GD-28 will be distributed to a mailing list of about 1,000 individuals and organizations.
For additional information please contact: Roger Barry, Director, WDC-A for Glaciology, CIRES/NSIDC, University of Colorado, Campus Box 449, Boulder, CO, 80309-0449, or (303) 492-5488 (phone), or (303) 492-2468 (fax), or Internet: email@example.com.
For copies of GD-28, ($15), please contact NSIDC User Services.
The International Permafrost Association (IPA) is a 20-member non-governmental organization founded in 1983 to disseminate knowledge of permafrost, seasonal frost, artificial ground freezing, and periglacial phenomena. One of the IPA's long-term goals is to retrieve, organize and disseminate frozen ground data at local, regional and global scales. To accomplish this, the IPA Working Group on Data and Information is developing a Global Geocryological Database (GGD), in cooperation with other IPA working groups and national and international organizations.
Why Do We Need the GGD?
Permafrost underlies about 25% of the Earth's surface. Permafrost research is interdisciplinary in character, multinational in execution, and regional or global in significance. Data on permafrost collected over many decades have current vital scientific, engineering, economic and societal significance. However, many of these data sets remain widely dispersed and relatively unavailable, and some are in danger of being lost permanently.
How Does the GGD Operate?
The GGD identifies existing data sets, current and historic; rescues those that are at risk of being lost; manages the acquired data; and makes data available to the scientific and engineering communities, either in raw form or processed into specific usable forms. Standard data descriptions are held in national and international directories, and users access the data through a variety of modes and media. The IPA works with user communities to identify priorities for data rescue, acquisition and monitoring. Emphasis has been placed on retrieving data and time-series that are in danger of being lost.
Once identified and described, data sets are organized into standard file structures and accessed by an appropriate NGD (National Geocryological Database) or GGD regional node. Currently, the designated nodes are:
For further information, potential data providers or information users may contact Roger Barry at Internet: firstname.lastname@example.org, or (303) 492-5488 (phone) or (303) 492-2468 (fax).