Issues in the Integration of Research and Operational Satellite Systems for Climate Research Part I. Science and Design (2000) / Chapter Skim
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Land Cover
Land Cover
Pages 37-56
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From page 37... ...
that specifically address vegetation assessment are the Normalized Difference Vegetation Index (NDVI; a ratio of near-infrared and red reflectance where high index values relate to the absorption of photosynthetically active radiation, a property correlated with biomass and primary production) , Land Surface Temperature, Snow Cover and Depth, and Vegetation Index/ Surface Type, ranked in that order by the Land Discipline Panel in the February 1997 NPOESS Climate Measurement Workshop (NOAA, 1997~.
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models, ecosystem process models, vegetation canopy structure models, land-use models, and integrated assessment models.
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However, it is recognized that some ecosystems may manifest more transient local heterogeneity. The interactions between climate and land use affect the structure and function of ecosystems, which will drive changes in net primary productivity and net ecosystem productivity.
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Daily data at moderate resolutions can detect change where spatial changes are large, such as burn scars from Savannah or boreal fires (Justice et al., 1993; Roy et al., 1999; Kasischke and French, 1995. Very high spatial resolution data (defined as having a spatial resolution of less than 20 m)
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As a result, the global coverage is patchy, and data acquired by foreign ground stations are necessary to improve historical coverage. Landsat data have been the primary source for land-cover research at high spatial resolution, but the cost of commercialized Landsat data has been prohibitive for the research community.
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From page 42... ...
The cost of funding comprehensive field campaigns has limited the effort largely to the examples cited above; however, such experiments are essential to scientific advances. Ground data are also collected to validate satellite data products and provide vicarious calibration of satellite instruments (Justice et al., 1998a)
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New MODIS algorithms for vegetation indices, such as leaf area index/fraction of absorbed photosynthetically active radiation (LAI/FPAR) , net primary productivity, bidirectional reflectance distribution function/albedo, surface temperature, snow cover, fire, land cover and land-cover change, will provide the science community a new suite of high-priority science data products (Justice et al., 1998b)
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. In addition, a new initiative is being developed for the validation of NASA EOS data products.
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and has recently started to coordinate a global net primary productivity activity. The Global Terrestrial Observing System (GTOS)
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Additional Long-Term Measurement Needs Moderate Resolution The VIIRS EDRs fall short of what will be needed for climate-related land-cover and land-use studies at the end of the first decade of this new century. Important data products such as LAIIFPAR, fire, net primary productivity, and land surface reflectance have been developed for near-term missions but are missing from VIIRS.
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From page 48... ...
Because of the cost of data acquisition and archiving, commercial satellite vendors have not been able to provide the types of postevent time-series data required for characterizing landcover change. Therefore, if commercial sensors are to be the backbone in providing very-high-spatial-resolution data for the land remote-sensing community, it is essential to develop data purchase agreements that apply throughout the sensor lifetime, with the associated science acquisition strategy.
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Empirical Corrections Empirical atmospheric correction methods will continue to be integral to deriving surface reflectance and emission characteristics from satellite data. The high spatial resolution of many sensors and orientation and pointing knowledge, combined with location information of field measurements obtained from global positioning system satellites, will make it possible to calibrate sensor output accurately using vicarious methods and to validate specific pixels for specific data products.
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In addition, it requires continued acquisition of the standard in situ ecological data sets that have developed in the major field campaigns. Selecting globally distributed land-cover sites to evaluate ecosystem data products and to establish current vegetation conditions is more difficult than using the bare-earth desert sites often selected for vicarious sensor calibration.
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From page 51... ...
The EOS land community has adopted core land-validation sites representing a range of blames and atmospheric conditions that must be augmented and strengthened to validate future land-data products. Coordinated and periodic ground-based measurement of such variables as surface reflectance, LAI/FPAR, canopy structure land cover, fire-burned area, and net primary productivity will provide a critical component for assessing product accuracy.
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Improving estimates of vegetation phonology will reduce errors in net primary productivity and net ecosystem productivity. Direct measurement of biomass and vertical and horizontal vegetation structure is also needed to parameterize and validate ecosystem models.
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1989. Monitoring global land surface using Nimbus-7 37 GHz polarization difference.
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1985. Analysis of the phonology of global vegetation using meteorological satellite data.
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1985. African land cover classification using satellite data.
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1995. Preliminary study of spin up processes in land surface models with the first stage of the Project for Intercomparison of Land Surface Parameterization Schemes Phase l(a)
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