GCOS Implementation Plan - WMO

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Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) transmission of solar radiation in the soil-vegetation system. It is both a forcing variable controlling the climate and a sensitive indicator of environmental degradation. Albedo varies in space and time as a result of both natural processes (e.g., changes in solar position, snow cover, and vegetation growth) and human activities (e.g., clearing and planting forests, sowing and harvesting crops, burning rangeland, etc.). Land surface albedo is sometimes monitored in situ on a national basis, but these observations are not coordinated in a global network. Space agencies have been generating global albedo products, in particular, from the MODIS and MISR sensors from 2000 onwards and from Meteosat since the midnineties. Future products should be expected to deliver at least the same level of quality, for instance on the basis of the VIIRS instrument and current or future geostationary platforms, although the current lack of commitment to launch or to continue to operate multi-angular sensors seriously hampers the feasibility of delivering high-quality albedo products in the future. Daily-average surface albedo values have been derived experimentally from a single geostationary satellite using a state of the art algorithm designed at the European Commission Joint Research Centre (JRC). In response to a CGMS action, EUMETSAT has started to reprocess archives of observations from the Meteosat instrument, using that algorithm, in order to generate historical time series of broadband albedo over long periods of time. A separate preliminary investigation by EUMETSAT has also shown the feasibility of generating this ECV on a near-global basis, using multiple geostationary satellites. The Japanese Meteorological Agency has recently expressed interest in coordinating the reprocessing of existing historical archives to generate such a global product, over as long a period as possible, in the context of the Sustained Coordinated Processing of Environmental Satellite Data for Climate Monitoring (SCOPE-CM) initiative. Mono-angular multi-spectral sensors on polar-orbiting platforms usefully complement this monitoring system by providing more comprehensive spatial coverage. However, the accuracy of these estimates needs to be assessed, in particular, with respect to their sensitivity to perturbing factors because the algorithms used to generate albedo products from these systems typically rely on the accumulation of data over two weeks or more, when surface properties can change appreciably, e.g., with the occurrence or disappearance of snow on the ground. The generic term 'albedo' often refers to a variety of different geophysical variables, which correspond to different definitions and measurements. Climate models typically require the ratio of the outgoing flux of radiation over the incoming flux (known as the bihemispherical reflectance factor), in a couple of broad spectral bands, while actual measurements and currently available derived products correspond to hemispherical conical reflectance and directional hemispherical reflectance factors in a limited set of narrow spectral bands. Such products often depend on specific assumptions on the state of the atmosphere or on the relative contributions of diffuse and direct radiation. As of this writing, existing products generated by different instruments or space agencies at spatial resolutions ranging from 1 to 5 km lack consistency and exhibit small but consistent biases that need to be resolved. This calls for comprehensive evaluation of the corresponding algorithms, the comparison of these albedo estimates with in situ and other measurements, and the benchmarking and crosscomparison of these products. Progress along these lines will consolidate confidence in the algorithms and justify the reprocessing of existing archives to generate long and coherent time series of global albedo products at the best available resolution. A fully characterised and broadly accepted global albedo product will be very valuable not only for climate studies but also as a reference for further studies and as a benchmark for other sensors and instruments. Some research groups running land surface process models have already begun to assimilate these new satellite-derived albedo products into their schemes and have noted improvements in the models’ performance. Further collaboration between the scientific communities involved is expected to result in improved methods and data for assimilation and reanalysis purposes. This goal will also require extensive algorithm benchmarking and product validation activities, as well as concerted efforts to archive and make available such standardised albedo products to the weather, climate, and other scientific communities in a form readily usable by these models. Ocean albedo is discussed in the Ocean Colour ECV section. 120
Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) Action T24 [IP-04 T19] Action: Obtain, archive and make available in situ calibration/validation measurements and collocated albedo products from all space agencies generating such products; promote benchmarking activities to assess the quality and reliability of albedo products. Who: Space agencies in cooperation with CEOS WGCV. Time-Frame: Full benchmarking/intercomparison by 2012. Performance Indicator: Publication of inter-comparison/validation reports. Annual Cost Implications: 1-10M US$ (20% in non-Annex-I Parties). Comparing albedo products measured in situ with those derived from space platforms is fraught with difficulties because of the large differences in scale and spatial and temporal resolution, differences in measurement protocols, and other practical issues. Nevertheless, such efforts must be pursued to ensure that existing products remain clearly linked to in situ measurements, to allow comparisons between similar products derived from different instruments, to evaluate the quality of new products as they become available, and to test the performance of algorithms after they have been updated. Action T25 [IP-04 T21] Action: Implement globally coordinated and linked data processing to retrieve land surface albedo from a range of sensors on a daily and global basis using both archived and current Earth Observation systems. Who: Space agencies, through the CGMS and WMO Space Programme. Time-Frame: Reprocess archived data by 2012, then generate continuously. Performance Indicator: Completeness of archive. Annual Cost Implications: 1-10M US$ (Mainly by Annex-I Parties) ECV – Land Cover Land cover and its changes modify the services provided to human society (e.g., the provision of food and fibre, recreational opportunities, etc.), force climate by altering water and energy exchanges with the atmosphere, and change greenhouse gas and aerosol sources and sinks. Land-cover distribution is partly determined by regional climate, so changes in land cover may indicate climate change. Although land-cover change can be inferred using data from Earth observing satellites, currently available datasets vary in terms of data sources employed and spatial resolution and thematic content, have different types and patterns of thematic accuracy, and use different land-cover classification systems (although improvement has been made in using common standards). It is necessary, and feasible with present-day technology, to provide satellite-based optical systems at 10- 30 m resolution with temporal, spectral, and data acquisition characteristics that are consistent with previous systems. Commitments to short-term continuity of this class of observations, such as the Landsat Data Continuity Mission and Sentinel-2, are vital steps, although long-term commitments still need to be secured. The CEOS Land Surface Imaging Constellation has been instigated to promote the effective and comprehensive collection, distribution and application of space-acquired imagery of the land surface. Datasets characterising global land cover are currently produced at resolutions of between 250 m and 1 km by several space agencies in close cooperation with the research community (especially those research groups participating in the GTOS technical panel Global Observation of Forest and Land Cover Dynamics (GOFC-GOLD)). The lack of compatibility between these products makes it difficult to measure and monitor climate-induced or anthropogenic changes in land cover. A range of approaches has been adopted, e.g., centralized processing using a single method of image classification (e.g., MODLAND, GlobCover)and a distributed approach using a network of experts applying regionally specific methods (e.g., GLC2000). Using a single source of satellite imagery and a uniform classification algorithm has benefits in terms of consistency, but may not yield optimum results for all regions and all land-cover types. Automated land-cover characterisation and land-cover change monitoring thus remains a research priority. It is necessary that land-cover classification systems and the associated map legends adhere to internationally-agreed standards. 96 Such standards should eventually be agreed upon by the UN/ISO 96 http://www.fao.org/gtos/ECV-T09.html 121
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WORLD METEOROLOGICAL ORGANIZATION I
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FOREWORD This 2010 Update of the Im
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6. TERRESTRIAL CLIMATE OBSERVING SY
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Implementation Plan for the Global
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