In this Issue
PRODUCTS AND SERVICES
ARCTIC SYSTEM SCIENCE (ARCSS)
NSIDC has recently received a gridded 2-meter air temperature set, produced by the POLES (Polar Exchange at the Surface) program at the University of Washington. The POLES Arctic Gridded 2-Meter Air Temperature Data Set provides optimally interpolated 2-meter air temperatures on the EASE-Grid at intervals of 4 times daily for the years 1979 through 1992. The years following 1992 are in the process of being analyzed and beginning in 1996, the production of these fields will be taken over by the International Arctic Buoy Program also at the University of Washington.
The grid used for this data set is an extension of the EASE (Equal Area SSM/I Earth) grid used by NSIDC. (See NSIDC Notes, no. 8, Winter 1994, for details.) Each of the grid points is separated by about 200 km. The geographic domain of the data set includes the ice-covered portion of the Japan Sea, the Okhotsk and Bering seas, and with the exception of the Baltic, all of the ice-covered seas of the North Atlantic.
The sources of the temperature observations used in the scheme consist of data from land stations, ship observations from the Comprehensive Ocean-Atmosphere Data Set (COADS), Soviet North Pole (NP) drifting ice stations, and Arctic drifting buoys. The temperature observations were taken at 2-meter heights at the land and Soviet NP drifting ice stations, and at heights varying from tens of centimeters to about 3 meters above the surface for the buoys. Because the ice on which the buoys rest is thick, we make the assumption that the buoy temperatures are also 2-meter air temperatures. Although in 1991, the Soviet NP stations ceased operation, we feel that the recent deployment of the new vented drifting buoys makes up for this loss.
Given that the historical buoy data set does not include data very close to the Siberian coast, the quality of the data set is best away from this region. The data are either available from NSIDC, or via anonymous ftp at isbjorn.ocean.washington.edu and via the World Wide Web at http://psc.apl.washington.edu/poles/POLES.html. The data files are on the order of 35 Mb per year and require several minutes to transfer.
Esther Munoz and Seelye Martin
Daily and monthly ice concentration grids derived from the DMSP SSM/I brightness temperature polar stereographic gridded data on CD-ROM are now available via ftp. Using anonymous ftp, go to the directory /pub/DATA_SETS/DATA/SSMI on sidads.colorado.edu (IP address is 188.8.131.52). In the "F8" directory are the monthly ice concentration grids for 9 July 1987 to 31 December 1991. In the "F11/SEAICE" directory there are directories "DAILY" and "MONTHLY" containing ice concentration grids for 3 December 1991 to 30 November 1994. Additional data will be added as they are received and processed; check the ftp site for additions. When there is sufficient volume, the daily (and perhaps monthly) ice grids will be made available on CD-ROM as well.
Documentation for the DMSP SSM/I products from NSIDC has recently been updated. Seven Postscript files containing the revised version of the User's Guide are available via ftp. To obtain the PostScript files of the revised version, ftp to sidads.colorado.edu; go to the directory /pub/DATA_SETS/INFORMATION/SSMI. The User's Guide is contained in seven PostScript files with .ps as the filename extension. Please read the "00readme" file first. A hard copy of the revised version will be mailed to each current holder of the SSM/I CD-ROMs as soon as it is returned from the printer.
Users who are interested in receiving updates, corrections or the data on CD-ROM when it is available, should register with User Services. Please contact NSIDC User Services if you have questions about obtaining the ice concentration data or the documentation files.
We are happy to announce the availability of a comprehensive collection of utilities and supplemental data to assist you in the analysis and use of our SSM/I and SMMR brightness temperature and sea ice concentration data sets. This "tool kit" is available on our regular ftp server (sidads.colorado.edu) in subdirectory pub/DATA_SETS/DATA/SSMI/TOOLKIT, and will soon be accessible through our Web site. It includes many of the standard tools we have provided on diskettes and some CD-ROM volumes, including IDL tools for viewing the data, DOS tools such as "untar" and "uncompress" and some new utilities such as a conversion program to remove the DMSP F11 SSM/I brightness temperature images from HDF and a program that calculates the area of each grid cell in the polar stereographic grid. We are currently working to ensure that these tools work on a variety of UNIX-based and DOS computer platforms.
In addition to the utilities, the tool kit includes the complete set of supplemental data we offer with our passive microwave products. These include all the land and coastline masks we currently have available and the new latitude-longitude overlay files for use with image display software to determine the center point location of each grid cell. See NSIDC Notes, no. 14, Summer 1995, for more information about the land mask we use.
This tool kit will be updated continually to ensure that our passive microwave products are as useful as possible. For a complete list of the utilities and supplemental data and their applications, please see the README file in the TOOLKIT directory on our ftp server.
If you have any questions or comments, please contact NSIDC User Services.
In October 1990, NOAA and NASA instituted a research program for the study of earth systems, called Pathfinder. The NOAA/NASA Pathfinder project seeks to create data products that emulate the planned products of the upcoming Earth Observing System (EOS) mission using existing satellites. Its objectives are two-fold: to provide example data sets for algorithm development and testing of data distribution systems; and to initiate a time-series of important geophysical parameters which will be continued by the new sensors to be flown on the EOS platforms.
Recently, three Pathfinder grant awards were issued for polar products derived from several passive-radiation-measuring sensors: SMMR and SSM/I (flown on the Nimbus and DMSP satellite series), AVHRR, and TOVS (both flown on the NOAA polar orbiter series). See below for award titles and an acronym list. Each of these grants intends to establish a continuous, calibrated and verified, geophysical data product using published algorithms. As discussed below, these products are both related and complementary. For this reason, the investigators of the three grants are planning now to coordinate the output products to make combined use of them easier.
The AVHRR Polar Pathfinder will produce a multi-year record of daily sea-ice motion, ice surface temperature for both sea-ice and the ice sheets, and polar broadband albedo. The time period planned is 1982 to 1997, although this range may be restricted somewhat by data availability. Spatial resolution of the time-series products will be 5 km, based on 4-km resolution GAC data, and 1.25 km resolution, available for the last five years of the period, based on 1.1 km resolution LAC/HRPT data. Ice velocity vectors will be on somewhat coarser grids, since they are based on shifts in ice patterns measured on 10 10-pixel 'chips' from pairs of images. A cloud mask will also be produced as a secondary product.
The Passive Microwave Polar Pathfinder will process SMMR Level 1b data from a previous Pathfinder project, and extend processing of SSM/I data, to produce a 20-year record of passive microwave data in the EASE-Grid format at 25 km grid cell size and a supplemental 12.5 km grid for the 85 GHz channel. EASE-Grid brightness temperature data are available in three equal area projections, azimuthal for Northern and Southern Hemisphere and cylindrical for full global. The data set will span the time- period 1978 to 1998. This data set is described in detail, and example images are provided by accessing URL http://www-nsidc.colorado.edu. Additionally, proposals are submitted to generate a snow cover and snow thickness product from this standardized 20-year record.
The TOVS Pathfinder will produce an 18-year (1979 to 1997) data set of daily atmospheric temperature and humidity profiles, cloud-cover and boundary layer parameters over sea ice for the north polar regions (>60 degrees). Spatial resolution of the product will be 100 km. As with the other two Pathfinders above, extensive validation information and error estimates will be provided. A 20-month sample of this data set for the Pathfinder benchmark period, April 1987-November 1988, is currently available from NSIDC.
To coordinate the data products from these grants, we intend to generate compatible grids for the output products. For each project, the grids will match up precisely, differing only in pixel size. Thus, a single grid cell from the TOVS products will be exactly represented by four SSM/I brightness temperature grid cells, and 6400 (80 x 80) 1.25 km grid cells from the higher resolution AVHRR products. We also intend to provide utilities, documentation, and examples on how to combine and use variables from these products. We will further intercompare duplicate variables (e.g., cloud fraction, surface temperature) and discuss the advantages and potential biases in the data sets.
The output grids for all the products will be based on a Lambert equal-area azimuthal projection of the data that is already in use for the SSM/I data (the EASE-Grid, see Armstrong and Brodzik, 1995). The advantages of this projection stem from the fact that each pixel represents an equal area; therefore the areal extent of a particular feature, i.e., sea ice, clouds, a particular surface temperature range, may be determined by simply counting grid cells in the product image.
Armstrong, R.L., Brodzik, M. J., 1995. An earth- gridded SSM/I data set for cryospheric studies and global change monitoring. Advances in Space Research, 16(10): 155-163.
Polar Geophysical Products Derived From AVHRR Data. J. Maslanik, T. Scambos, J. Key, W. Emery.
Generation of Level 3 SMMR and SSM/I Brightness Temperatures for the Period 1978-1998. R. Armstrong.
TOVS Pathfinder Path-P: Gridded Daily and Monthly Arctic Atmospheric Data from TOVS. J. Francis, A. Schweiger.
|AVHRR||Advanced Very-High Resolution Radiometer|
|EASE||Equal Area SSM/I Earth (Grid)|
|GAC||Global Area Coverage|
|HRPT||High Resolution Picture Transmission|
|LAC||Local Area Coverage|
|SMMR||Scanning Multichannel Microwave Radiometer|
|SSM/I||Special Sensor Microwave/Imaging|
|TIROS||Television Infrared Operational Satellite|
|TOVS||TIROS Operational Vertical Sounder|
For more information regarding these data sets please see these WWW sites:
NSIDC has recently received Antarctic snow pit and snow cover data from Sally Whitlow, University of New Hampshire, via ftp. Data were collected at several sites, and we currently have data from three of them, Dominion Range, Newall Glacier and the South Pole. These data are now available from NSIDC.
For further information, contact NSIDC User Services.
The ARCSS Data Coordination Center at NSIDC and the Paleoclimatology Division of the National Geophysical Data Center (NGDC) have developed a location on the World Wide Web where researchers can access any available ice core data held by either group http://www.ngdc.noaa.gov/paleo/ice-data.html. This page is also accessible via a link from either the NGDC Paleoclimate homepage or the ARCSS homepage at NSIDC. The data for which each organization has responsibility are still at their respective location (GISP2 data at NSIDC, all other ice core data at NGDC), but all approved data sets are available through either page. These links facilitate data distribution to the scientific community, without having redundant archives at each data center.
Now accessible through this ice core homepage are the new and improved Crete and Milcent ice core data from Dave Fischer, Geological Survey of Canada, via Jim White, INSTAAR. Data from the Agassiz, Camp Century, and Dye-3 cores are also included.
Dave McGinnis and Matt Cross, ARCSS Data Coordination Center at NSIDC, participated in three ARCSS-related Workshops this quarter.
GISP2 and GRIP investigators presented and discussed their latest research results from data obtained from the Greenland ice cores. Much has been learned about past climates from each of the cores, and most of the information obtained from the GISP2 and GRIP cores will be published in a special issue of the Journal of Geophysical Research (JGR) in late 1996. The ARCSS Data Coordination Center at NSIDC hopes to produce a CD-ROM of ice core data from the GISP2 and GRIP cores, and to have it available in conjunction with the special issue of JGR. We are currently contacting each GISP2 investigator directly to finalize plans for data migration to NSIDC so that this ice core CD-ROM can be produced.
HARC is a component of the NSF-funded ARCSS project, formulated to incorporate the human element within the framework of the Arctic system. The meeting focused on organizing the group into a cohesive body, providing an overview of current research in the Arctic, and determining the best avenues for integration with the other components of ARCSS.
The staff of the ARCSS Data Coordination Center at NSIDC attended to help define what role the Coordination Center would play in HARC, to make the HARC investigators aware of the services provided to ARCSS and to discuss the possibilities of integrated research with other ARCSS components. Dave McGinnis was asked to be part of the Education committee related to HARC.
Coordination of the project goals within the LAII Flux Study to maximize the integration among Flux Study investigators was the main focus of the meeting. Due to the varied data types that exist within the LAII/Flux Study project many data issues were discussed during the meeting, including: data formats (ASCII, spreadsheet, GIS formats), data distribution policies (release dates, data availability outside of ARCSS), and distribution media (CD-ROM, WWW access, tape). All of these issues are being resolved through communication with each of the investigators through the ARCSS listserver.
The World Atlas of Snow and Ice Resources, under the direction of Editor-in-chief, Vladimir Kotlyakov, of the Institute of Geography, Russian Academy of Sciences, is nearing completion. Publication of this comprehensive work is expected in 1996/97.
The Atlas discusses the principal glaciological characteristics of the globe, the distribution of snow and ice and their importance as a fresh water resource, and the relations between ice and climate, temperature, precipitation and altitude.
The Atlas comprises over one thousand maps in various scales, from global coverage to specialized maps of regions such as the Alps, Caucasus, Pamirs or Alaska. This cartographic volume is accompanied by a separate text volume in English and Russian. A booklet in English will give the title, caption and legend of every map.
The final price for the Atlas will be several hundred dollars (US), but the exact cost has not yet been set. If you are interested in the Atlas, please contact the following address for additional information:
Institute of Geography
Russian Academy of Sciences
Moscow 109017 Russia
Telex: 411781 Globe SU
Fax: [7-095] 230-2090