GCOS Implementation Plan - WMO

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Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) better (modern sensors offer the possibility of systematically generating global products at a spatial resolution of about 300 m). FAPAR is recovered from a range of sensors by various algorithms using the visible and infrared parts of the spectrum, and the accuracy and reliability of these products is not always properly documented. Currently available products have been shown to exhibit significant differences, which detract from their usefulness in downstream applications. The CEOS WGCV, in collaboration with GCOS and GTOS, should lead the comparison and evaluation of these FAPAR products as well as the benchmarking of the algorithms used to generate them. Reference sites making in situ observations should be fully engaged in this process, and it would be desirable if these sites were collocated with the terrestrial reference sites proposed in Action T3, provided that these sites offer a reasonable degree of spatial homogeneity over spatial scales comparable to the resolution of the sensors. WGCV is identifying a core set of sites and measurement campaigns, which should be supported by the CEOS agencies and by national research budgets. Relatively homogeneous sites, at scales comparable to the typical spatial resolution of modern sensors, are preferable, but a detailed characterisation of the spatial variability of those sites is required. Action T29 [IP-04 T29] 98 Action: Establish a calibration/validation network of in situ reference sites for FAPAR and LAI and conduct systematic, comprehensive evaluation campaigns to understand and resolve differences between the products and increase their accuracy. Who: Parties’ national and regional research centres, in cooperation with space agencies coordinated by CEOS WGCV, GCOS and GTOS. Time-Frame: Network operational by 2012. Performance Indicator: Data available to analysis centres. Annual Cost Implications: 1-10M US$ (40% in non-Annex-I Parties). ECV – Leaf Area Index (LAI) LAI measures the amount of plant leaf material in an ecosystem. It is typically expressed as a nondimensional value giving the number of square metres of leaf material per square metre of ground. This variable plays important roles in models that represent processes, such as photosynthesis, respiration and rain interception, that couple vegetation to the climate system through the radiation, carbon, and water cycles. Hence, LAI appears as a key variable in many models describing vegetation-atmosphere interactions. LAI can be estimated in situ by destructive sampling or with the help of commercially available dedicated instruments. It is routinely measured at a number of research sites dealing with surface climate, ecological, or agricultural issues. CEOS WGCV is playing a coordinating role in this work. Benchmarking and consistency checking are required for the global archive of LAI measurements. For reasons set out below, in some parts of the globe (e.g., in the humid Tropics), LAI can only be measured by in situ methods. However, the measurement network is sparse in many regions of the world. It should be maintained and ideally expanded to become much more representative of the diversity of ecosystem conditions. The development and maintenance of reference sites to address this inadequacy should be addressed, as explained elsewhere in this document. Building on existing networks, such as FLUXNET, LAInet and BIGFOOT, is a possible way to improve this situation (see Action T3). The CEOS WGCV has begun to coordinate this through the creation of a centralized database, an activity that should continue. The retrieval of reliable LAI estimates from space remains difficult. When the canopy cover is sparse, reflectance measurements are dominated by soil properties, and the accuracy of the LAI is low. When LAI values exceed 3 or 4, optical measurements lose their sensitivity to changes in LAI (signal saturation. Also, since the LAI measured by satellites is usually inferred from spectral reflectances in the visible and infrared spectrum, it is de facto coupled to FAPAR estimates, even though both variables are in principle independent and play quite different roles in the climate system. Nonetheless, regular global LAI estimates from space are currently being produced, and this effort 98 See Action T3. 124
Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (2010 Update) should be continued (it requires little extra resource above that required to produce FAPAR). These LAI products have the same spatial resolutions (250 m-1 km) and temporal frequencies (7 to 10 days) as the FAPAR products. Recent research is exploring the feasibility of estimating LAI (and aboveground biomass) from microwave sensors, and these efforts should also be pursued. Benchmarking and comparison of these LAI products is essential to resolve differences between products and to ensure their accuracy and reliability. The CEOS WGCV should lead this activity in collaboration with GCOS and GTOS, exploiting in situ observations from designated reference sites and building on the validation activities currently being undertaken by the space agencies and associated research programmes. Action T30 [IP-04 T30] Action: Evaluate the various LAI satellite products and benchmark them against in situ measurements to arrive at an agreed operational product. Who: Parties’ national and regional research centres, in cooperation with space agencies and CEOS WGCV, TOPC, and GTOS. Time-Frame: Benchmark by 2012. Performance Indicator: Agreement on operational product. Annual Cost Implications: 1-10M US$ (10% in non-Annex-I Parties). Action T31 [IP-04 T28] Action: Operationalize the generation of FAPAR and LAI products as gridded global products at spatial resolution of 2 km or better over time periods as long as possible. Who: Space agencies, coordinated through CEOS WGCV, with advice from GCOS and GTOS. Time-Frame: 2012. Performance Indicator: One or more countries or operational data providers accept the charge of generating, maintaining, and distributing global FAPAR products. Annual Cost Implications: 10-30M US$ (10% in non-Annex-I Parties). ECV – Above-ground Biomass Vegetation above-ground biomass is a crucial ecological variable for understanding the evolution and potential future changes of the climate system. Vegetation biomass is a global store of carbon comparable in size to atmospheric carbon, while changes in the amount of vegetation biomass due to deforestation significantly affect the global atmosphere by acting as a net source of carbon. Vegetation systems have the potential either to sequester carbon in the future or to become an even larger source. Depending on the quantity of biomass, vegetation cover can have a direct influence on local, regional, and even global climate, particularly on air temperature and water vapour. Therefore, a global assessment of biomass and its dynamics is an essential input to climate change prognostic models and mitigation and adaptation strategies. Biomass plays two major roles in the climate system: (a) photosynthesis withdraws CO 2 from the atmosphere and stores it as biomass, some of which goes into long-term stores in the soil; (b) the quantity of biomass consumed by fire affects CO 2 , other trace gases, e.g., CH 4 , CO, and aerosol emissions. Only above-ground biomass is measurable with some accuracy at the broad scale, while belowground biomass stores a large part of total carbon stocks and is rarely measured. Most nations have schemes to estimate woody biomass through forest inventories (little is recorded on non-forest biomass, except through agricultural yield statistics). This typically forms the basis for the annual reporting on forest resources required by the UNFCCC. Experimental airborne sensors have demonstrated technologies for estimating biomass (low-frequency radar, lidar) and are suitable for satellite implementation that could provide global above-ground biomass information at sub-kilometre resolutions. There are limitations to these technologies, of which some are known (for example, saturation of radar backscatter at higher levels of biomass) and some still the subject of research. National inventories of biomass differ greatly in definitions, standards, and quality, and the detailed information available at national level is normally unavailable internationally. Nonetheless, these form 125
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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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GCOS Implementation Plan - WMO

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