HR: 0800h
AN: B51B-0205    [Abstracts]
TI: Development of a Daily MODIS BRDF/Albedo Algorithm
AU: * Strahler, A
EM: alan@bu.edu
AF: Department of Geography Boston University, 675 Commonwealth Ave, Boston, MA 02215 United States
AB: The operational MODIS algorithm retrieves 500m BRDF model parameters from all high-quality, cloud-free, atmospherically-corrected surface reflectances acquired during a 16-day period. The reprocessed V005 product will make use of any observations from Terra and Aqua from March 2000 to present and will serve as the best representation of the surface anisotropy possible during each 16-day period. However, for certain real time applications required by Direct Broadcast and future NPP/NPOESS, users there is a need for accurate daily products of surface albedo and view zenith angle-corrected surface reflectances (such as the Nadir BRDF-Adjusted Reflectance, or NBAR). One solution is to use the retrieved periodic BRDF model parameters as an a priori first guess of the surface anisotropy and then combine the periodic BRDF with successive single-day observations to provide realistic daily retrievals. By testing the impact of the observations from any single day, ephemeral or abrupt changes (such as snowfall, flooding, harvest, or burning) can be flagged and accommodated. The periodic BRDF parameters can be retrieved every 16 days or in a more rolling fashion (such as every 8 (or fewer) days based on the last 16 days of observations) and then coupled with single-day observations for each day following until a new high-quality periodic BRDF is retrieved. This method allows for a more dynamic representation of the surface anisotropy than any method using BRDFs based on land cover types or previous year climatologies. Furthermore, the two-part processing chain lets the periodic BRDFs be retrieved in the background while the single-day retrievals can be performed in a rapid real time fashion. Some regional case studies will be presented and the variations over the seasons will be discussed.
DE: 0360 Radiation: transmission and scattering
DE: 0429 Climate dynamics (1620)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: Fall Meeting 2005