Global Terrestrial Observing System Research Articles

An approach for the long-term 30-m land surface snow-free albedo retrieval from historic Landsat surface reflectance and MODIS-based a priori anisotropy knowledge

Land surface albedo has been recognized by the Global Terrestrial Observing System (GTOS) as an essential climate variable crucial for accurate modeling and monitoring of the Earth's radiative budget. While global climate studies can leverage albedo datasets from MODIS, VIIRS, and other coarse-resolution sensors, many applications in heterogeneous environments can benefit from higher-resolution albedo products derived from Landsat. We previously developed a “MODIS-concurrent” approach for the 30-meter albedo estimation which relied on combining post-2000 Landsat data with MODIS Bidirectional Reflectance Distribution Function (BRDF) information. Here we present a “pre-MODIS era” approach to extend 30-m surface albedo generation in time back to the 1980s, through an a priori anisotropy Look-Up Table (LUT) built up from the high quality MCD43A BRDF estimates over representative homogenous regions. Each entry in the LUT reflects a unique combination of land cover, seasonality, terrain information, disturbance age and type, and Landsat optical spectral bands. An initial conceptual LUT was created for the Pacific Northwest (PNW) of the United States and provides BRDF shapes estimated from MODIS observations for undisturbed and disturbed surface types (including recovery trajectories of burned areas and non-fire disturbances). By accepting the assumption of a generally invariant BRDF shape for similar land surface structures as a priori information, spectral white-sky and black-sky albedos are derived through albedo-to-nadir reflectance ratios as a bridge between the Landsat and MODIS scale. A further narrow-to-broadband conversion based on radiative transfer simulations is adopted to produce broadband albedos at visible, near infrared, and shortwave regimes. We evaluate the accuracy of resultant Landsat albedo using available field measurements at forested AmeriFlux stations in the PNW region, and examine the consistency of the surface albedo generated by this approach respectively with that from the “concurrent” approach and the coincident MODIS operational surface albedo products. Using the tower measurements as reference, the derived Landsat 30-m snow-free shortwave broadband albedo yields an absolute accuracy of 0.02 with a root mean square error less than 0.016 and a bias of no more than 0.007. A further cross-comparison over individual scenes shows that the retrieved white sky shortwave albedo from the “pre-MODIS era” LUT approach is highly consistent (R2=0.988, the scene-averaged low RMSE=0.009 and bias=−0.005) with that generated by the earlier “concurrent” approach. The Landsat albedo also exhibits more detailed landscape texture and a wider dynamic range of albedo values than the coincident 500-m MODIS operational products (MCD43A3), especially in the heterogeneous regions. Collectively, the “pre-MODIS” LUT and “concurrent” approaches provide a practical way to retrieve long-term Landsat albedo from the historic Landsat archives as far back as the 1980s, as well as the current Landsat-8 mission, and thus support investigations into the evolution of the albedo of terrestrial biomes at fine resolution.

Temperature data acquired from the DOI/GTN-P Deep Borehole Array on the Arctic Slope of Alaska, 1973–2013

Abstract. A homogeneous set of temperature measurements obtained from the DOI/GTN-P Deep Borehole Array between 1973 and 2013 is presented; DOI/GTN-P is the US Department of the Interior contribution to the Global Terrestrial Network for Permafrost (GTN-P). The 23-element array is located on the Arctic Slope of Alaska, a region of cold continuous permafrost. Most of the monitoring wells are situated on the Arctic coastal plain between the Brooks Range and the Arctic Ocean, while others are in the foothills to the south. The data represent the true temperatures in the wellbores and surrounding rocks at the time of the measurements; they have not been corrected to remove the thermal disturbance caused by drilling the wells. With a few exceptions, the drilling disturbance is estimated to have been on the order of 0.1 K or less by 1989. Thus, most of the temperature measurements acquired during the last 25 yr are little affected by the drilling disturbance. The data contribute to ongoing efforts to monitor changes in the thermal state of permafrost in both hemispheres by the Global Terrestrial Network for Permafrost, one of the primary subnetworks of the Global Terrestrial Observing System (GTOS). The data will also be useful for refining our basic understanding of the physical conditions in permafrost in Arctic Alaska, as well as providing important information for validating predictive models used for climate impact assessments. The processed data are available from the Advanced Cooperative Arctic Data and Information Service (ACADIS) repository at doi:10.5065/D6N014HK.

Recent contributions to cryospheric research in Switzerland : introduction to the special issue

The cryosphere includes important elements of the earth system like sea ice, lake and river ice, snow cover, solid precipitation, glaciers, ice caps, ice sheets, per¬ mafrost and seasonally frozen ground. Changes of the cryospheric elements influence energy, moisture, gas and particle fluxes, clouds, precipitation, hydrological conditions and circulation patterns in the atmosphere and the ocean. With current interest in the impact of cli¬ mate change, the limelight has also settled on the cryo¬ sphere due to the strong visibility of changes in nature here, even for non scientists Haeberli 2008). Changes observed in our climate affect the cryosphere on differ¬ ent scales Global Climate Observing System GCOS/ Global Terrestrial Observing System GTOS 2004; Key et al. 2007; Solomon et al. 2007). On a global scale, glaciers, ice caps and ice sheets are increasingly contrib¬ uting towards sea level rise and are therefore threaten¬ ing many heavily populated regions close to seashores. On a local to supraregional scale, the current retreat of mountain glaciers influences sustainable agriculture and energy production; and locally, mountain permafrost is affecting slope stability Organe consultatif sur les changements climatiques OcCC/ ProClim 2007).

Observation Needs for Climate Information, Prediction and Application: Capabilities of Existing and Future Observing Systems

The demand for long-term, sustained, reliable data and derived information on climate and its changes has never been greater than today. Long-term, well-calibrated, global observations of Essential Climate Variables (ECV) such as air temperature, precipitation, and sea-surface temperature are critical for defining the evolving state of the Earth's climate. Observing systems routinely collect much of the required data covering 49 ECVs, and significant progress has been made in coverage and technological capability over the two decades since the Second World Climate Conference. However, many key regions and climatic zones remain poorly observed, and gaps are widening in some cases. Supporting infrastructures for data stewardship and analysis are largely in place but require strengthening, while those for linking with socio-economic data and for providing user-oriented information services require more substantial development. The current capabilities are summarized, and further actions are identified to ensure that climate observation activities more fully meet the needs of science and society. The Global Climate Observing System (GCOS) was established in 1992 with the goal of providing comprehensive information on the total climate system, involving a multidisciplinary range of physical, chemical and biological observations of the atmosphere, oceans and land. GCOS is a “system of systems” that builds on the climate-relevant components of existing observing systems, and relies almost entirely upon national efforts to maintain and enhance those systems. Contributing systems include the World Meteorological Organization Global Observing System (GOS) for meteorology, its Global Atmosphere Watch (GAW) for atmospheric composition, the Global Ocean Observing System (GOOS), led by the United Nations Educational, Scientific and Cultural Organization (UNESCO) Intergovernmental Oceanographic Commission (IOC), and the Global Terrestrial Observing System (GTOS), led by the Food and Agriculture Organization of the United Nations (FAO). GCOS itself is the climate observing system within the Global Earth Observation System of Systems (GEOSS) developed under the auspices of the Group on Earth Observations (GEO). The established in situ networks and space-based components must be sustained and operated with ongoing attention to data quality in accordance with the GCOS Climate Monitoring Principles; enhancements must be made for some types of observations; the exchange of observations and delivery of data and information to users must be ensured; reprocessing and reanalysis must be strengthened; and national and international coordination must be improved. The consequence of not meeting these requirements would be to seriously compromise the information on, and predictions of, climate variability and change. Detailed information on GCOS and the datasets that are produced as a result of GCOS observing activities can be found at the Global Observing Systems Information Center (GOSIC) at http://gosic.org.

Evolving standards in land cover characterization

Reliable observations of the terrestrial environment are of crucial importance to understanding climate change and its impacts, to sustainable economic development, natural resources management, conservation, biodiversity and a scientific understanding of ecosystems and biogeochemical cycling. GOFC-GOLD (Global Observations of Forest Cover and Land Dynamics) as panel of GTOS (Global Terrestrial Observing System) and the Global Land Cover Network of FAO-UNEP (GLCN) brings together key participants and stake-holders involved in global land cover observations. The objective is to provide a platform for cooperation and communication on current and planned activities including developments on the political programs, international strategic frameworks as well as related implementation initiatives. Harmonization and validation of land cover datasets are central implementation issues.

Contribution of the NASA Land-Cover/Land-Use Change Program to the Northern Eurasia Earth Science Partnership Initiative: An overview

The Northern Eurasia Earth Science Partnership Initiative (NEESPI) is a rapidly growing program that involves national government agencies, academia and private organizations in the U.S., Europe, Japan and Northern Eurasia. During the last decade the Northern Eurasian region have been undergoing socioeconomic, climatic and demographic changes. The causes of these changes, the associated interactions between the land surface, the atmosphere and the surrounding ocean and the resultant impact on the sustainability of land use of the region are important topics for scientific research. The NEESPI Science Plan has been prepared as an integrated regional study to better understand these hemispheric-scale interactions, to evaluate the combined role of climate and anthropogenic impacts on the Northern Eurasia ecosystems, and to assess how future human actions would affect the global climate and ecosystems of the region. Projections of the consequence of global changes on the regional environment, the economy and the quality of life in Northern Eurasia that is of primary importance to the nations in the region is an additional focus of this initiative. The NASA Land-Cover/Land-Use Change (LCLUC) Program has supported NEESPI since its inception, and currently funds 26 NEESPI projects. Several other NASA programs are also currently supporting or planning to support the NEESPI. The NEESPI program links to the major international programs under the Earth System Science Partnership (IGBP, IHDP, DIVERSITAS and WCRP) and under the Global Terrestrial Observing System, such as the Global Observation of Forest Cover/Global Observation of Landcover Dynamics (GOFC/GOLD). A number of the NEESPI science activities are aligned with the Global Earth System of Systems (GEOSS) objectives, giving an emphasis to societal benefits, so that the NEESPI framework can serve as a regional test bed for international cooperation in developing a system of observational systems. Since it is a new program, most of the NEESPI research projects have just started. Therefore, rather than describing these projects this paper focuses on presenting some results of the longer term projects which are being continued under NEESPI, and on the expected products from the program and its future directions. More information on the projects can be found at http://neespi.org or http://lcluc.hq.nasa.gov.

Evaluation of national and global LAI products derived from optical remote sensing instruments over Canada

Leaf area index (LAI) is an important surface variable for monitoring the status of vegetation and as input in a number of ecosystem process models. There are currently several coarse-resolution LAI maps over Canada, including a Canada Centre for Remote Sensing ten-day, 1-km resolution, Canada-wide product based on SPOT-4 VEGETATION (VGT), a MODIS eight-day, 1-km resolution, global product and a monthly, 7-km resolution, global map produced using POLDER-1. These products are difficult to validate because of their large spatial extent and coarse resolution. In this study we use in situ LAI measurements collected over a wide range of forest types and ecological zones in Canada to derive 30-m resolution reference LAI maps based on robust error-in-measurement regressions to Landsat Enhanced Thematic Mapper Plus vegetation indices. The reference maps and LAI products were aggregated to a coarser resolution (3 km for MODIS and VGT and 7 km for POLDER) before comparison to account for registration errors, and variability in sensor projected point spread functions. Spatially corresponding aggregated pixels with both high-quality reference and coarse scale LAI retrievals were compared. The comparison shows reasonable agreement (biases less than 25% or one LAI) between the VGT and reference LAI. The MODIS LAI product showed weak correlations (R2<0.25) over all sites at the scale of comparison and typically overestimated reference LAI in mixed forests by approximately 200%. The POLDER LAI product, only available in June 1997, showed almost no correlation to the summer reference LAI datasets. It underestimated reference LAI for an early growing season with an extent, in some cases, greater than the seasonal differences in LAI. This independent validation of three large area LAI products suggests that there may be substantial biases due to the lack of regional tuning of retrieval algorithms. These biases are far larger than the uncertainties in the reference-based LAI scenes in the case of the MODIS product. This suggests that reliable LAI maps may require regional calibration to meet the Global Terrestrial Observing System mapping requirements of plusmn15% uncertainties

Beyond the Mediterranean to global observations of coastal lagoons

The United Nations has begun addressing the detection and prediction of global and large-scale change through the development of observing systems. The three observing systems are the Global Climate Observing System (GCOS); the Global Ocean Observing System (GOOS); and the Global Terrestrial Observing System (GTOS). Each of these is designed to be a ‘8user-driven, end-to-end’ system, providing measurements of selected variables and indicators, management and communication of these, and their analysis and synthesis into products for users. The interface between the land and ocean provides complexities that affect the capabilities of the three global observing systems. Understanding the complex interactions between natural and human systems at various scales is central to successful management of the coast in the face of change. Both GOOS and GTOS have organized initiatives for the coast with the GOOS initiative (CGOOS) being more developed. CGOOS is built upon a global network, which focuses on a limited number of phenomena and their associated variables, and regional programs that contribute to the global network and focus on other phenomena. CGTOS (coastal GTOS) has identified a few key phenomena for the development of the future mature system. These phenomena are linked to a framework that incorporates socio-economic variables into the program. To establish proof of concept and early success by CGTOS, four priority products have been identified that address (1) transport of materials, (2) functional typology, (3) integrated assessments of cultural and conservation sites, and (4) assessment of human populations and land use and land cover. The coastal observing systems are in the stages of developing implementation plans and should be operable in coming years.

Coastal initiative of the Global Terrestrial Observing System

The three global observing systems (the Global Climate Observing System (GCOS); the Global Oceanographic Observing System (GOOS); and the Global Terrestrial Observing System (GTOS)) are designed to detect and assess global change. A land-based coastal observing system initiative under GTOS is at the beginnings and will lead toward the integration of terrestrial and freshwater observations with marine observations under the auspices of coastal GOOS. The GTOS infrastructure already builds on national, regional and global programs for terrestrial observations, but more emphasis is needed on the unique circumstances of coastal ecosystems. Coastal GTOS will use the observing system philosophy and infrastructure to identify and improve access to data and information about coastal change; assist users to make that access systematically; ensure that appropriate measures are being or can be made; and integrate terrestrial observations with marine observations. Key variables have been defined for GTOS. But major challenges include evaluating these and others for coastal ecosystems and identifying the indicators of coastal condition that operate at appropriate scales.

The terrestrial ecosystem monitoring sites: a utility assessment

Ecological research sites generate data which are potentially useful at the national, regional and global scales. However, most of the data remain embedded in local, project-specific research programmes. The primary role of the Global Terrestrial Observing System (GTOS) is to act as a data broker and bring researchers and modellers together in order to better understand global change processes in areas such as climate change and biodiversity. The Terrestrial Ecosystem Monitoring Sites (TEMS) database is a GTOS-led effort to enhance the ability of sites to collaborate and provide a framework for researchers, resource managers and decision makers who seek data to support their efforts at the regional and global levels. Early in 2002, a user survey was carried out to assess the use of the TEMS database, the adequacy of geographic coverage and identify future user requirements. The survey also assessed the utility of specific features within the website such as the environmental variables methodology sheets, the search engines and the dynamic map interface. The results confirmed that TEMS contains useful information which can be easily accessed. The registered sites are under-represented, on both an eco-regional and continental basis, in all geographic areas except for Europe and Northern America. Data sharing, including satellite imagery, was indicated to be of high priority; however, free access to data remains a constraint in some regions. Finally, a focus on electronic solicitation and outreach should be continued.

Further possibilities through UNEP for promoting the role of developing countries in conduct of ground-based experiments in support of utilization of global satellite data

This paper describes various components and some of the planned activities of the United Nations Environment Programme in global environmental assessment. An operational Global Terrestrial Observing System (GTOS) will provide the observational framework and data basis for addressing issues related to environment conservation and sustainable development.

A Scientific Approach to Employ Monitoring and Modelling Techniques for Global Change and Terrestrial Ecosystems and Other Related Projects

The ultimate goal of understanding processes in the Earth's geophysical/biogeochemical/climate system can be achieved by multi-disciplinary studies using global monitoring systems, regional networks and models merging scientific and technological issues. The Global Climate Observing System (GCOS) and its composite parts-Global Ocean Observing System (GOOS) and Global Terrestrial Observing System (GTOS)-are on the agenda of current and subsequent international efforts. To outline scientifically the construction of the systems, an approach is proposed that includes the following interrelated blocks: Climate/Biosphere Models, Observation Systems, Geoinformation Systems and Predictability Problems. The opportunity to unify these blocks in the general context of global/regional change studies are determined by the proposed application of the information and thermodynamic properties of the entropy category that reveals its dualism in the information content assessments for data of modelling/ monitoring and in state parameter retrievals for natural targets using multi-spectral remote sensing images. The Climate/Biosphere Models block is designed to highlight how global and regional change problems are drawn up in terms of models, data, and processes for natural media (the atmosphere, hydrosphere, land surface, biosphere). The Observation Systems block, linking modelling and monitoring quantities on various scales, serves to account for recommendations to optimization techniques based on certain criteria, value functions and information content metrics. The recommendations are due to the necessity to improve or make cost-effective the systems which are planned within the EOS (Earth Observing System) and similar other programmes. The Geoinformation Systems (GIS) block gives an explanation to what extent GIS-technologies, databases and information systems can be unified with general principles of data processing, related algorithms and procedures. The Predictability Problems block enables one to understand what can be determined from temporal data set analyses and inter-annual variability of multi-spectral satellite products and samples of ground mea-