Coordinating Satellite Observations during the International Polar Year 2007-2008
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|Figure 1. An illustration of the ranges within the|
electromagnetic spectrum in which optical and
microwave airborne and polar orbiting satellite
remote sensing observations are being acquired
The 2007-2008 International Polar Year (IPY) provides an international framework for improving our understanding of high-latitude climate change and enhancing our skill in predicting world-wide impacts. Recent, well documented observations of the dramatically changing high-latitude components of earth’s cryosphere (e.g., those areas where water is frozen either seasonally or permanently) make IPY science investigations particularly timely and relevant to scientists, policy makers and the general public. Effective IPY investigations require a range of commitments of resources: from providing support to individual field activities, to those which require the international coordination of complex systems and their operations. During IPY, to date considerable progress is being made towards characterization of key high-latitude processes by means of spaceborne snapshots of the polar regions. A number of ongoing efforts are described below which are designed to coordinate these satellite acquisitions, to help demonstrate the benefits of a cryospheric observing system component, and to develop IPY data legacy comprising critical climate benchmarks.
The Global Interagency IPY Polar Snapshot Year
|Figure 2. Composite meteorological satellite|
image products from GOES, Meteosat, DMSP,
AVHRR, produced routinely at different spatial
resolutions and at regular intervals of 3 hours
(Courtesy U. Wisconsin-Madison and ESA Polar
The Global Interagency IPY Polar Snapshot Year (GIIPSY) is a World Meteorological Organization (WMO)/International Council for Science (ICSU) approved IPY Project whose objective is to obtain high-resolution, broad spectral snapshots of the polar regions during 2007-2008 (Figure 1). Our primary purpose is to use these snapshots as gauges for comparing past and future environmental changes in the polar ice, ocean, and land. In the spirit of IPY, we also seek to secure these data sets as our legacy to the next generations of polar scientists.
GIIPSY comprises polar scientists from around the world who have assembled a consolidated list of thematic objectives (Table 1) that call upon the collective resources of international space agencies. Our programmatic goal is to identify ways in which the resources of space-faring countries can be used in such a way as to collect data with which to address these scientific objectives, without putting undo burden on any single organisation. To that end, we seek cooperation in terms of spaceborne instruments, data relay systems, ground segments, processing, and data archiving and distribution capabilities.
A general description of the GIIPSY programme and its current status and progress can be found on-line at http://bprc.osu.edu/rsl/GIIPSY. Detailed scientific driving requirements and objectives for the satellite observations were derived from pre-IPY town hall meetings (e.g. AGU December 2006), discussions with other science planning groups including IGOS (Goodison, 2007, IGOS, 2007), and wide-ranging debate within the GIIPSY science community. The complete set of requirements are documented in Table 1 and in subsequent publications and presentations (Jezek and Drinkwater, 2006, Jezek and Drinkwater, 2007, Farness, Jezek and Drinkwater, 2007). Together, we have taken the detailed science requirements and distilled them into a set of thematic objectives, which are listed in Table 1. Topics range from permafrost to sea ice and include several objectives that would be the first of their kind.
In order to fulfil the scientific objectives described above, carefully coordinated data acquisitions over both the northern and southern hemisphere are required using the broad range of available satellite instrument capabilities. This is best achieved using polar-orbiting satellites that routinely acquire image or other instrument data over the high-latitude regions along approximately 14 crossing orbits each day.
Operational meteorological satellites equipped with the AVHRR optical imager such as NOAA-15 and MetOp acquire data which are routinely composited to provide complete polar coverage at intervals of up to a few hours (see Figure 2). Such overlapping images acquired by meteorological satellites are used to track large-scale cloud motion (Figure 3) when the surface is cloud-covered. Meanwhile, other higher resolution satellite optical instruments may be used to capture ice sheet movement (Figure 4) in instances when the surface is not obscured by clouds. Optical data are complemented by all-weather, day or night data acquired using satellite microwave radar or radiometers. Figure 5 indicates an entire Arctic mosaic and regional details of sea-ice conditions using microwave synthetic aperture radar (SAR) image data, whilst Figure 6 shows how pairs of high resolution SAR may be used interferometrically, to reveal streaming ice flow in Antarctica.
Figure 7 shows how the products derived from multi-satellite, multi-frequency satellite data may be plotted on a virtual Earth to fully capture the state of various elements of the cryosphere. Many such products are now routinely available in Google for convenient viewing of current status of the entire polar region.
Space Task Group
Interaction between GIIPSY and the international space agencies is coordinated through the IPY Space Task Group (STG), which is convened by the WMO. A number of meetings have taken place between the following Space Agency members and participating organisations: China Meteorological Administration (CMA), the Centre National d’Etudes Spatiales (CNES), the Canadian Space Agency (CSA), the German Aerospace Center (DLR), the European Space Agency (ESA), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), the Russian Federal Service for Hydrometeorology and Environmental Monitoring (ROSHYDROMET), the World Climate Research Programme (WCRP), and WMO. Meanwhile, we have approached several other agencies about joining the federated efforts of the STG, including Agenzie Spaziale Italiana (ASI), the Instituto Nacional de Pesquisas Espaciais (INPE), the Indian Space Research Organisation (ISRO), the Japan Aerospace Exploration Agency (JAXA), and the U.S. Geological Service (USGS).
The STG has agreed upon three important programmatic activities. First, the STG adopted the GIIPSY science requirements for guiding agency data acquisition planning. Second, the agencies are populating individual IPY “data portfolios”. Individual portfolios represent best efforts given agency resources and strategic mandates, but in total the goal is to fulfil them. By collaborating, the combined portfolios will represent a more complete response to the GIIPSY requirements. Most recently, the Space agencies have agreed to try to develop a coordinated acquisition strategy for high data rate instruments. The idea is to distribute the image acquisition burden across several agencies.
Current progress towards achieving a data legacy is identified in the form of the portfolio contents already assembled on the GIIPSY web site. Image examples acquired during 2007 which are shown here, illustrate the broad range of products that will constitute the IPY data legacy.
The Cryosphere Component of GEOSS
Leading up to the IPY, one of the key near-term goals of the World Climate Research Programme’s Climate and Cryosphere (CliC) Project has been to develop an Integrated Global Observing Strategy Theme on Cryosphere known as IGOS-Cryo (IGOS, 2007). The ongoing Polar Year provides a unique chance to illustrate the benefits of coordinated observations by a range of polar observing systems, comprising in-situ, airborne, or satellite-borne measurement capabilities. CliC together with the Scientific Committee on Antarctic Research (SCAR) are developing a conceptual framework and vision for a sustained Cryosphere Observing System, known as CryOS. The initial phase of development of CryOS coincides with IPY.
IPY has facilitated the establishment of a Cryospheric system of systems which embodies the vision of the Global Earth Observing System of Systems (GEOSS). In this context, GIIPSY makes a vital contribution to CryOS by addressing the challenge of the inter-agency planning and coordination of observing infrastructure which is required to deliver a critical high-latitude element of the observing system.
The recent pace of changes observed in the polar regions has stimulated global interest in the International Polar Year. It is also exactly 50 years since the technical triumph of Sputnik and the International Geophysical Year. The confluence of international science programs, technical capabilities in satellite remote sensing, and IPY therefore present an extremely valuable opportunity for gathering data essential to understanding the changing polar climate and its global impact.
IPY uniquely federates scientific activities across 63 nations while the IPY Space Task Group and the GIIPSY IPY Project are actively harnessing the technical capabilities of the world’s Space Agencies and the specialist knowledge of their science communities to obtain a unique legacy data suite- or ‘polar snapshot’, comprising a broad range of satellite products. This data legacy will provide the opportunity to engage a new generation of researchers, experts, educators, policy makers, and polar residents in understanding the polar regions and changes in its environment, as well as the global consequences of these changes.
2007 Jezek, K.C., K. Farness, and M. Drinkwater. Global Interagency IPY Polar Snapshot Year: Goals and Accomplishments. Geophysical Research Abstracts, Vol 9. 01444, EGU, Vienna.
2007 Jezek, K.C. and M. Drinkwater. Global Interagency International Polar Year Polar Snapshot Year (GIIPSY). ASF News and Notes, Summer 2007, Vol 4:2, p. 2-3.
2006 Jezek, K.C., and M. Drinkwater Global Interagency IPY Polar Snapshot Year, EOS, Vol 87, Issue 50, p. 566.
2007 Goodison, B., J. Brown, K. Jezek, J Key, T. Prowse, A. Snorrason, and T. Worby. State and fate of the polar cryosphere, including variability of the Arctic hydrologic cycle. WMO Bulletin, vol. 56(4), p. 284-292.
2007 IGOS, Integrated Global Observing Strategy Cryosphere Theme Report – For the Monitoring of our Environment from Space and from Earth. Geneva: World Meteorological Organization. WMO/TD-No. 1405. 100 pp.
|Table 1. GIIPSY Thematic Objectives Derived from GIIPSY Science Requirements|
|A. Sea level rise, and hemispheric climate (Glaciers, ice caps, ice sheets):|
1) For the first time, one summer, one winter SAR snapshot of the polar ice sheets, glaciers and ice caps. Near simultaneous imagery at L, C, and X band, in various polarizations for documenting ice surface physical parameters.
2) For the first time, pole-to-coast multi-frequency InSAR measurements of ice surface velocity.
3) For the first time, repeated X-band InSAR topography for detecting local changes in ice sheet elevation associated with motion of subglacial water.
4) For the first time, one summer, one winter, high resolution visible/near IR/ TIR snapshot of the entirety of the polar ice sheets, glaciers and small ice caps followed with bi-monthly coverage of select glaciers for snow-zone mapping.
5) Continued measurements of ice surface elevation from radar and laser altimeters (spaceborne and airborne) for volume change.
6) Continued, daily visible and infrared medium-resolution imaging of the entirety of the polar ice sheets, glaciers and ice caps and to be compiled into monthly maps.
7) Continued, daily medium-to-coarse resolution active and passive microwave images of the polar ice sheets, ice fields and ice caps for melt extent.
8 ) Continued measurements of the gravity field for mass balance.
|B. Ocean circulation and polar air-sea interactions (Sea ice):|
1) For the first time, L-band SAR mapping of the Arctic ocean and marginal seas sea ice cover for leads and ridges.
2) For the first time, repeat fine resolution SAR mapping of the entire Southern ocean sea ice cover for ice motion.
3) For the first time, SAR and optical fine resolution mappings of the entire Arctic ocean.
4) Continued 3-day medium resolution SAR mapping of sea ice covered waters for motion, and melt pond coverage.
5) Continued passive microwave observations of sea ice concentration and extent.
6) Continued laser and radar altimeter measurements of ice thickness and sea surface topography.
7) Measurements of IPY Polar Geoid.
|C. Regional climate, precipitation and hydrology (Terrestrial snow cover):|
1) Daily medium resolution visible/near IR/TIR observations of all snow covered terrain.
2) Daily passive microwave observations of snow covered terrain for determination of snow water equivalent.
|D. Changing permafrost and Arctic climate (Permafrost):|
1) For the first time, one complete high resolution snapshot of all polar permafrost terrain at L, C and X band.
2) For the first time, one complete, high resolution visible and thermal IR snapshot of all polar permafrost terrain.
3) Continued medium and coarse active and passive microwave observations of all polar permafrost.
|E. Aquatic ecosystems, transportation and hazards (Lake and river ice):|
1) For the first time, pan-arctic high and medium resolution microwave snapshots of fresh water- break/freeze-up.
2) For the first time, pan-arctic high and medium resolution visible, near IR and TIR snapshots of fresh water- break/freeze-up.
3) Seasonal, low-frequency (6-10 GHz) passive microwave observations of lake ice thickness.
This article has been prepared on behalf of the IPY Space Task Group, whose fundamental contributions are acknowledged in this endeavour. Without the contributions of these Space Agencies and other organisations, this effort would not be possible.
Further details about Agency portfolios and access to data products may be obtained at the Global Interagency IPY Polar Snapshot web site.
By Mark R. Drinkwater1 and Ken Jezek2
1 – European Space Agency, Earth Observation Programmes, Mission Science Division. Email: firstname.lastname@example.org
2 – Byrd Polar Research Center, Ohio State University