INTRODUCTION
On November 4-5, the User Working Group for the National Snow and Ice Data Center (NSIDC) Distributed Active Archive Center (DAAC) met in Boulder, Colorado. The following briefly recounts the discussions held and recommendations offered to the NSIDC DAAC.
Research Announcements, Bob Thomas, NASA HQ: NASA is moving towards fixed deadlines for research proposal submissions. A coordinated Sea Ice Research Announcement (RA) will be published in Spring `97 for funding in `98, and an Ice Sheet RA is planned to be released in Summer `97 for funding in `98. The science oversight and the budget control for the five Polar Pathfinders will be moved from GSFC to NASA Headquarters, under Thoma's leadership.
NSIDC Update, Roger Barry: DAAC activity highlights of the past six months include the following accomplishments: SSM/I Polar Stereo Grid Tb's and ice concentrations have been processed and distributed through September, 1995; an SSM/I sea ice products team has been formed (J. Maslanik, J. Stroeve, Li); SMMR Ta's and Tb's have been transferred from the MSFC DAAC to the NSIDC DAAC; a total of 15,600 polar AVHRR scenes has been processed and archived and DOMSAT data ingest for AVHRR 1 km data is now active. The DAAC Yearbook has been produced and distributed, and five new hires have been brought aboard: for data coordination (A. Nolin, T. Zhang), for the sea ice product team (J. Stroeve, X. Li), and an ECS System Engineer (L. Head, Hughes employee). The user request statistics showed a slight decrease in `96 (1385) compared to `95 (1500), but a total of 822 new users was registered.
New Mission Data Coordinators: As mentioned in the update report, NSIDC has hired two Ph.D.-level scientists to augment the DAAC's capability to interface to Instrument Teams and to service data sets and products. Anne Nolin will coordinate data products at NSIDC for the planned MTPE missions, MISR and GLAS, and related altimetry data. Her science interests are in dynamic albedo changes, snow energy/mass balance modeling, modeling the snow bidirectional reflectance distribution function (BRDF), and snow cover mapping at sub-pixel resolution. Tingjun Zhang will coordinate land-based in situ data and validation efforts at NSIDC. His science interests are in Arctic climate change, snow, ice, and permafrost, and heat and mass transfer in porous media.
Alaska SAR Facility Update, Kim Partington: ASF user services will be enhanced (new position). No data have been delivered in the 3rd quarter of CY 96 due to major problems with the system upgrade. JERS-1 data have been processed and delivered; ERS-1/2 data will be processed later this month. RADARSAT uncali- brated data will be distributed on request to the Applications Development and Research Opportunity (ADRO) project PIs in December. RADARSAT SCAN SAR B data will be calibrated first, and processing and distribution are scheduled for April 1, 1997.
Cryospheric Working Group, Barry Goodison: The cryospheric chapter of the EOS Science Plan was discussed and a revised outline presented. Several experiments need to be added to the chapter (8.3.2) on surface observations and field experiments (e.g., PARCA (see below), WAIS, others?). The final deadline for this chapter is November 30, 1996. Further, the Chair of the Cryospheric Working Group is still vacant. The Polar DAAC Advisory Group (PoDAG) has agreed to coordinate and chair the Cryospheric Working Group until a new chair has been found. See http://www-nsidc.colorado.edu/NASA/CRYOSPHERIC_CHAPTER.
SSM/I Polar Stereo Grid Processing, Jim Maslanik: SSM/I brightness temperatures for F8 and F11 have been distributed on CD-ROMs. F13 SSM/I Tb's (May '95 - June '96) will be distributed on CD by December 1, 1996. A new enhanced ice concentration CD series with F8, F11, and F13 with NASA Team- and Bootstrap-derived values is scheduled for February 1, 1997. Quality control issues were discussed, such as weather effects, land contamination, and data set consistency.
Workshop on Sea Ice Observations, Ron Weaver, Koni Steffen: New techniques will be tested and implemented in the coming 4-5 years that supersede the current algorithms, offering greater accuracy and resolution. Existing empirically-based passive microwave sea ice algorithms can be improved by incorporating new methods which exploit the full spectrum of remote-sensing data and modeling (data assimilation). The proposal was made to organize a workshop at NSIDC to promote new ideas for the study of the Arctic sea ice cover. The PoDAG members proposed selecting a workshop organization committee and discussing possible agenda items. The workshop would be held no sooner than December 1997.
SMMR Pathfinder vs. GSFC Tb's, Ron Weaver: The Pathfinder and GSFC SMMR Tb histograms gave the following differences: 2 K (37V), 5 K (18H), and 3.5 K (18V). There were some pixels with differences above 10 K. The largest differences were found over open ocean; the smallest differences over sea ice. This suggests that the differences arise from different ocean radiative transfer models used by Per Gloerson (GSFC) and Eni Njoku (JPL). PoDAG proposed looking for the cause of this difference in more detail.
SSM/I F11 and F13 Intercomparison, Julienne Stroeve: For the months of July, August, and September 1995, a common data set for two different SSM/I instruments (F11 & F13) is available. The equator crossing time for F11 is 6:25 p.m., and for F13, 5:43 p.m. The intercom-parison of brightness temperatures was done for regions over the Greenland and Antarctic ice sheets, and for sea ice regions in the Arctic and Antarctic. The F11 and F13 data sets are highly correlated, with best correlation for the Antarctic ice sheet, and least correlation for the Arctic sea ice region. Using ice sheet coefficients, slight regional biases remained, and larger discrepancies in multi-year ice concentration resulted. Using sea ice coefficients, the regional sea ice biases were eliminated, but larger weather effects were obvious. Without adjustments, the F11 and F13 sea ice extent and total sea ice area agree within 2%. Currently, the NSIDC F11-derived sea ice products incorporate the regression coefficients of Abdalati et al., based on an intercomparison of F8 and F11 (December time period) over the Greenland ice sheet. PoDAG proposed to use globally-derived coefficients, employing techniques developed by F. Wentz.
HDF Format Survey, Claire Hanson: The survey was sent to 618 users, and 74 responses were received (12% response rate). About 70% of users are using commercial software, and 30% are using freeware to display HDF format data. In general, 55% of the users have an overall positive experience with the HDF format, 14% reported a negative experience, and 31% had no opinion. Most of the PC and MAC users recommended the development of the EOS View Tool, which currently is only planned for UNIX systems. NSIDC made tools available for HDF conversion on the NSIDC ftp site.
GLIMS, Bruce Raup: The Global Land Ice Monitoring from Space (GLIMS) project proposes to monitor most glaciers and ice sheet margins on Earth once a year throughout the lifetime of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The amount of ASTER data required annually for GLIMS glacier monitoring is only 1.5% of the collected ASTER Level 1A, but still accounts for 82 Gbytes/year. The anticipated GLIMS database of 550 Mbytes will consist of 10 variables from 100,000 glaciers over a 5-year period. The resulting data set will be archived at the NSIDC DAAC. The GLIMS coordination center resides at USGS in Flagstaff, whereas most of the data processing will be done at the regional centers all over the globe. See http://wwwflag.wr.usgs.gov/GLIMS/glimshome.html.
Coordination of Polar Pathfinder, Axel Schweiger: The purpose of this coordination effort is to maximize the scientific value of the polar Pathfinder data sets by making them easy to use in combination. The participating Pathfinder projects are TOVS, SSM/I-SMMR Ice, AVHRR, and SSM/I-SMMR Atmosphere. A common multi-resolution grid structure has been defined with standardized file names, variable names, and file formats. Further, a common data set has been proposed (P-CUBE), with 100-km resolution containing most relevant variables from all data sets. See http://www-nsidc.colorado.edu/NASA/POLAR_ PATHFINDER.
POLES Update, Drew Rothrock: The Polar Exchange at the Sea Surface (POLES) interdisciplinary investigation studies the lower troposphere, the sea ice cover, and the high-latitude oceans. Intercomparisons of different cloud and radiative flux density data sets reveal large discrepancies of up to 0.25 cloud fraction, and 50 W/m2 flux density, respectively, independent of season. However, the flux density needs to be known with a mean monthly rms error of less than 10 W/m2 during winter for sea ice modeling. The POLES cloud detection and masking algorithm was quoted with an accuracy of 0.15 cloud fraction during winter. Further, comparison between individual observations of flux densities and coincident AVHRR-derived flux values for downwelling shortwave radiative flux showed good correlation (0.99), with -4.2 W/m2 bias, and rms error of 32 W/m2. A similar comparison was done for longwave radiative flux from TOVS data, showing a bias of -3 W/m2, and standard deviation of 23 W/m2. See http://psc.apl.washington.edu/poles/.
RGPS Update, Drew Rothrock, Kim Partington: The RADARSAT Geophysical Processor System (RGPS) is using ScanSAR B data to derive ice products once a week for the entire Arctic. Data acquisition started on October 24, 1996. The five data products from RGPS on a weekly 5-km grid will comprise 2-3 Gbytes per year. See http://psc.apl.washington.edu/RGPS/.
CRYSYS Update, Barry Goodison: The Cryospheric System (CRYSYS) to Monitor Global Change in Canada involves over 30 active participants from government and universities. The scientific goals of CRYSYS are: to develop capabilities for monitoring and understanding variations in cryospheric processes (regional to global scale); to develop and validate climate processes and dynamics; and to analyze various data sets (historical, operational, and research) for climate monitoring and model validation. Several time series were discussed: arctic sea ice concentration derived from passive microwave; ice and snow thickness variations from observations and modeling (Resolute Bay, NWT); and snow water equivalent derived from airborne microwave measurements.
K-12 Outreach, Alex Weaver: Basic problems with K-12 outreach are that teachers have very little time and money, that many (especially K-6) have only a limited science background, and that they need current science content and guidance in using it in the classroom. Although individual PoDAG researchers make excellent contributions to the K-12 community, there is little funding for a coordinated effort by NSIDC, for example. NSIDC User Services currently limit their K-12 outreach work, because staff and resources are not available for a more extensive effort. Worthwhile projects (like the partially completed "Avalanches" resource) are postponed indefinitely because of the lack of staff time and funding. Some suggestions on how to improve the outreach were: continue to support national-scale projects, e.g., CIESIN; provide teachers' workshops to support the use of the "Sea Ice in the Polar Regions/Arctic Observatory" CD-ROM; encourage improvements in NASA curriculum materials, e.g., prepare new lithograph on Polar Ice; revise activities on the Sea Surface Temperature lithograph; and revise the Polar Ice Fact Sheet. It is important that funding agencies recognize these needs and provide long-term support for K-12 activities.
Landsat 7 Polar Application, Ted Scambos: Recently, a grant was funded to map changes in the Antarctic using Landsat imagery. A main objective will be to map the outflow velocities in West Antarctica, using a cross-correlation feature-mapping algorithm. The MTPE project will be accomplished over the course of three years. Financial support of $20,000/year was requested for a data specialist to convert the derived ice motion data. The data would than be made available to the polar community through the NSIDC DAAC.
SSM/I Snow Melt Product, Mark Anderson: A new passive microwave data product to classify the onset date of snow melt in the Arctic ocean region was presented. The data set will be a valuable addition for the present ice concentration data set, as the ice concentration algorithm performs poorly under snow melting conditions. The NSIDC DAAC was urged to make this low-density data set available to the community.
PARCA Greenland Climate Data Set, Koni Steffen: The Program for Arctic Regional Climate Assessment has deployed a number of automatic weather stations on the Greenland ice sheet. The Greenland Climate Network (GC-Net) will collect data over the next 4 to 5 years from a total of 14 stations, with 500 parameters transmitted hourly via satellite links. It is proposed to archive the original data set at the NSIDC DAAC, and to produce a Greenland climate CD-ROM with GC-Net data and auxiliary data sets from meteorological stations around Greenland. See http://cires. colorado.edu/parca.html.
RECOMMENDATIONS
PoDAG Meetings: Future PoDAG meetings will be held 8 months apart. Important issues will be discussed via telecom when needed. We encourage NSIDC to support sub-group meetings of PoDAG members to resolve urgent action item issues between the PoDAG meetings. The next PoDAG meeting will be in Boulder, in third week of June 1997.
PoDAG Co-Chair: Dave Bromwich agreed to act as Co-Chair of PoDAG during the sabbatical leave of the present chair.
EASE Grid SSM/I CD-ROM Distribution: PoDAG recommended continuing the Equal Area SSM/I Earth (EASE) Grid CD-ROM distribution. However, the community should be questioned if it needs all three data sets (northern Hemisphere, southern Hemisphere, and global). To reduce production cost, users should be asked to be more rigorous with their selection.
Workshop on Sea Ice Data Assimilation: A small working group/organizing committee should meet in the spring to define the goals of the workshop.
SSM/I Polar Stereo Grid Processing: NSIDC should provide a climatological mask to flag weather effects in open ocean areas for daily ice concentration production. For the weekly ice concentrations, two different data sets should be provided: a) derived product with no masking, and b) derived product with climatological mask applied to flag weather effects in open ocean areas.
Landsat 7 Antarctic Data Set: PoDAG did not recommend supporting the financial request for a DAAC-funded data person for this project; however, PoDAG encouraged making the West Antarctic ice motion data set available through the NSIDC DAAC, when the relevant research is completed.
SSM/I Snow Melt Product: PoDAG recommends that the passive microwave snow melt time series produced by Mark Anderson be made available for distribution through the NSIDC DAAC.
ACTION ITEMS
SMMR Pathfinder vs. GSFC SMMR Tb's, J. Stroeve:
Compare radiative transfer code for Pathfinder and GSFC SMMR data processing. Try to evaluate if the Tb difference for the two data sets is the result of different coding. Get community expertise if required. Report findings by February `97.
Polar Pathfinder Common Tools, R. Weaver:
The Polar Pathfinder group proposed a common tool to access their data: (e.g., variables, region, dates, resolution). NSIDC should provide a cost estimate to develop this tool, assuming that the Pathfinder group would provide their data in a common data format which is accessible for the tool.
SSM/I F11 and F13 Intercomparison, J. Maslanik: Contact F. Wentz to learn when the global F11 vs. F13 intercomparison, coefficients will become available. Work an alternative plan to derive these coefficients at NSIDC if timing is crucial. Report on telecom in January 1997.