In this Issue



Issue 3, Fall 1992


U.S. Air Force funding was received at the National Geophysical Data Center (NGDC) in support of the Digital DMSP Data Archive Program, adding significantly to NASA, NOAA and other DOD funds already in hand at NGDC and NSIDC for this effort. NSIDC and NGDC are jointly involved in this program to make digital DMSP data available to the user community.

A team of scientists, data managers and software programmers are designing the archive and user services components of this program. NSIDC recently added two new staff to the effort, and the new funds will permit the continued involvement of a software subcontractor and the procurement of much needed hardware.

Beginning in September of 1992, Air Force Global Weather Central began routine copying of DMSP data to 8 mm tapes. We expect that a several month backlog of data will accumulate during this development phase, but we hope to announce the availability of preliminary user services in the Spring or early Summer of 1993. User services for data related to the climate-cryosphere system will be provided by NSIDC.

For more information, contact: Greg Scharfen at (303) 492-6197 or Internet:


SSM/I Sea Ice Concentration Grids

Volumes 14 and 15 of daily SSM/I brightness temperature grids are being mailed to subscribers the week of 7 December. These two CD-ROMs cover the period 1 October 1990 to 31 March 1991. Watch your mailbox!

If you are not currently a subscriber and would like more information about this passive microwave sea ice data product, contact: Michelle Holm of NSIDC User Services at (303) 492-2366 or Internet:

Volume 14 Error

One of the grids that is being distributed on Volume 14 of the SSM/I Brightness Temperature Grids for the Polar Regions CD-ROM series was corrupted during the CD-ROM pre-mastering process. The N3B grid file (Northern Hemisphere grid containing the 19, 22 and 37 GHz channels) for 09 December 1990 contains a section of the N3B grid representing 07 December 1990. The data are accurate in the archive and must have been corrupted sometime between the process of transferring the data via ftp to the pre-mastering environment and the process of creating the ISO image disk partition. The file containing the correct information will be provided on volume 16 of the CD-ROM series.

The correct version of the file is in anonymous ftp account our DADS system. The file, 901209.n3b, is located in the anonymous ftp directory ../pub/ssmi and can be retrieved from the Internet host "". The file will remain available via anonymous ftp until volume 16 of the CD-ROM series has been distributed.

Instructions for obtaining the correct version of the grid contained in file 901208.n3b follow.

%ftp <Return>
220 FTP server ready
Name ( your username): ftp <Return>
331 guest login ok, type your name as password:
Password: username <Return>
230 guest login ok, access restrictions apply
ftp> cd pub/ssmi <Return>
250 CWD command successful.
ftp> binary
200 Type set to 1. ftp> get 901209.n3b
200 Port command successful
150 Opening BINARY mode data connection for '901209.n3b' (1361920 bytes)
226 Transfer complete.
1361920 bytes received in 1.60 seconds (829.29 Kbytes/s)
ftp> quit
221 Goodbye

For further information, contact: Vince Troisi at (303) 492-1827 or Internet:

New Capabilities Ahead in 1993

A Silicon Graphics Incorporated (SGI) Power Series computer was installed at the NSIDC facility. This system, which operates under the UNIX kernel, is being configured to support the distribution of data on a variety of tape media including 8mm, 4mm DAT, 3480, and the old- reliable 2400 foot 1/2" tape reel (6250 bpi).

Tape media will not be the only form of distributing data to the research community. NSIDC plans to provide access to data by staging a limited volume of data on-line. The individual who initiating the data request will be able to retrieve the data over the Internet using the TCP/IP utility, FTP.

NSIDC plans on making these new services available Spring 1993.

Hint for New Users of SSM/I CD-ROMs

If you have difficulty accessing the SSM/I Brightness Temperature CD-ROMs using the program GETSSMI.FOR, please note that this program requires you to enter a colon (:) after the letter of your CD-ROM drive in response to its prompt. Without the colon, the program terminates with the error message "run-time error F6416: OPEN(L \<PATHNAME>)" after it prompts the user for the date of the archive file to open.

When CD-ROM volume 16 is mailed to subscribers, the package will include corrected pages to insert in the User's Guide that note this requirement and correct several other recently-noted errors or omissions.


Claire Hanson has been invited to represent NSIDC on the ARCSS OAII Steering Committee. This should provide a closer connection between the OAII investigators and NSIDC in all aspects of OAII planning that include data management issues. The ARCSS data management philosophy at NSIDC is to work as diligently as possible to enhance communication channels with the ARCSS community in order to provide the types of data products and services that will meet research requirements.

NSIDC will also be represented at the ARCSS LAII Flux Program planning meeting in Seattle, 16-17 January 1993. Involvement of NSIDC at the early planning stages of the Flux Program will provide a focus on data management issues that need to be addressed at the outset if the resulting flux data sets and data products are to be easily distributed to and used by ARCSS investigators, and ultimately a wider user community.

For more information, contact NSIDC User Services.


For those of you interested in iceberg data, NSIDC has just received an updated data set from the International Ice Patrol (IIP). The IIP iceberg tracking database spanning 1960 to the present is now available in a single file for 1960 to 1991. Beginning with 1992 data, each year will be in a separate file. The entire database can be obtained on 1 reel of 9-track tape; 1990 - 1992 data are also available on PC diskettes. Please inquire for a price quote.

The new version of the database was developed at IIP to standardize all existing iceberg sighting data into one format without losing any information. Fields included in the new record format include iceberg number, sighting index, resight (Y or N), sighting source, sighting position, sighting time, iceberg description (9 classes), last model analysis position, number of bergs in the sighting record, days on plot, and date of last model position.

The new database was developed for use with the IIP iceberg drift model, and some fields (i.e. "days on plot", "last model analysis position") are derived from the model itself. A complete description of the database is available on request from NSIDC, and is supplied with all orders for the iceberg data.

The U.S. Coast Guard has operated the IIP in the area 40 degrees 52 degrees North, 39 degrees - 57 degrees West since 1914, following the sinking of RMS Titanic in iceberg-infested waters.

For more information, contact NSIDC User Services.


Application of Special Sensor Microwave Image (SSM/I) Data for Snow Cover

In October 1992 NSIDC distributed a CD-ROM containing DMSP SSM/I gridded brightness temperature data in a prototype format. The CD-ROM contains sample data giving global coverage of the first 18 days of December 1989. The prototype is named the EASE-Grid (Equal Area SSM/I Earth Grid) and has been distributed to approximately 150 researchers who have been asked to evaluate the usefulness of the format in their research environment and return comments to NSIDC. The primary purpose of this distribution is to provide a candidate example of an optimal format for the distribution of earth-gridded SSM/I data and products.

The method used in the EASE-Grid resamples SSM/I swath data to points on an equal area earth grid while maintaining the spatial characteristics of the original data. The technique applies the actual antenna pattern correction coefficients to the swath data (antenna temperatures) to create an oversampled array of brightness temperatures from which the assignment is made to earth grid cells by the nearest neighbor method. The EASE-Grid retains sample spacings (40km, 20km, 10km for the 19 and 22 GHz, 37 GHz, 85 Ghz respectively) which are appropriate for the EFOV of the SSM/I channels.

The prototype contains data in two candidate projections, Azimuthal Equal Area (separate northern and southern hemispheres) for applications at high latitudes and Cylindrical Equal Area for applications at low to mid-latitudes.

The main intent of this prototype distribution is to solicit input on the interpolation, data storage format, earth grid scheme and the projections of the EASE-Grids. We welcome inquiries from anyone who has not received the prototype and would like to evaluate the format.

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


Annual Report

The NSIDC Annual Report 1992 has been published. A limited number of copies are available for general distribution.

If you are interested in receiving a copy, contact NSIDC User Services.

Sea Ice Workshop

Thorndike, A.S., C. Parkinson and D.A. Rothrock (1992) Report of the Sea Ice Thickness Workshop, 19-21 November 1991, New Carrollton, Maryland.

This report summarizes our present capability to measure the thickness, and reviews the role ice thickness plays in regulating the interaction of polar atmospheres and oceans. Copies are available from: Polar Science Center, Applied Physics Laboratory, University of Washington, 1013 NE 40th St., Seattle, WA 98105-6698. Telephone: (206) 543-1300.