Data Supporting the Validation of MODIS Land Products

Data from multiple types of local and regional studies are needed to extrapolate from site studies to larger-scale products derived from remote sensing or global-scale modeling. This poster describes data compiled at the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) to support the validation of MODIS land products. The ORNL DAAC provides data from several sources to support this effort: (1) a global network of flux tower sites (FLUXNET), (2) subsets of remote sensing products from MODIS, (3) ground-based studies designed to validate remote sensing products, and (4) regional and global data set of key environmental parameters. The FLUXNET database contains carbon, water vapor, sensible heat, momentum, and radiation flux measurements along with associated ancillary and value-added data products for a wide range of ecosystems on five continents. Subsets of selected MODIS products are provided in ASCII format for an area 7 x 7 km around each of 274 field sites. The MODIS products posted at the ORNL DAAC include surface temperature, reflectance, albedo, vegetation indices, land cover, leaf area index, photosynthetically active radiation, and photosynthesis. Data collected from land validation field studies are registered in the DAAC's Mercury metadata search and data retrieval system. Data on the global distribution of net primary production and leaf area index, based on 1000s of point measurements, are available from the ORNL DAAC for use in validation. Validation of MODIS Products has benefited from the use of core validation sites, where a suite of field, airborne, and satellite data is used to extrapolate from site studies to large-scale products. Existing in situ networks (e.g. flux towers, AERONET, LTER/ILTER) and field investigations (e.g., LBA, SAFARI 2000) as well as international partnerships and coordination, mainly through CEOS/IGOS, have been key components of the validation approach. We have learned that simplified data access with dedicated archives and easy-to-use data formats (e.g., ASCII subsets) as well as frequent communication between Product PIs, Validation PIs, and data facilitators all play a significant role in improving the understanding of the MODIS Land Products.