HR: 0800h
AN: B51B-0199    [Abstracts]
TI: BIOPHYS/LANDSAT: A Physically-Based Algorithm for Inferring Continuous Fields of Vegetation Biophysical Parameter From Landsat Data
AU: * Hall, F G
EM: Fghall@ltpmail.gsfc.nasa.gov
AF: JCET/UMBC, Goddard Space Flight Center, 8600 Greenbelt Rd, Greenbelt, Md 20771 United States
AU: Huemmrich, K F
EM: Karl.F.Huemmrich.1@gsfc.nasa.gov
AF: JCET/UMBC, Goddard Space Flight Center, 8600 Greenbelt Rd, Greenbelt, Md 20771 United States
AU: Landis, D R
EM: David.R.Landis.1@gsfc.nasa.gov
AF: Science Systems and Applications, Inc., Goddard Space Flight Center, 8600 Greenbelt Rd, Greenbelt, Md 20771
AU: Peddle, D
EM: derek.peddle@uleth.ca
AF: University of Lethbridge University of Lethbridge University of Lethbridge, 4401 University Drive West, Lethbridge, Al T1K3M4 Canada
AU: Masek, J G
EM: Jeffrey.G.Masek.1@gsfc.nasa.gov
AF: NASA Goddard Space Flight Center, 8600 Greenbelt Rd, Greenbelt, Md 20771 United States
AB: We develop and test BIOPHYS/Landsat, an innovative, physically-based algorithm for inferring from Landsat surface reflectance fields, continuous fields of vegetative biophysical and structure parameters for input to surface/atmosphere carbon water and energy exchange models. BIOPHYS is a two-stage inference engine. Continuous parameter fields inferred in the first stage consist of only those characterizing radiative transfer in a vegetated canopy; canopy and background optical properties, percent canopy cover, crown green leaf area index, crown height to width ratio and branch area index. From these parameters, the second stage of BIOPHYS calculates fields of derived biophysical parameters relevant to carbon, water and energy transfer; albedo, fraction of absorbed photosynthetically active radiation (Fapar), average green leaf area index, roughness length etc. BIOPHYS handles non-unique solutions by averaging over the solutions to obtain a mean value for the parameter, then directly calculates error statistics from the parameter variance over the non-unique solution space. The advantages to BIOPHYS/Landsat include (i) robustness over time and space. BIOPHYS accounts directly for the effects of global variations in illumination conditions (topography, sun angle etc.), a key requirement of any global scale algorithm; (ii) training data are not required; (iii) continuous fields of biophysical parameter and land cover type deduced from the fields are provided in a fully integrated algorithm, providing increased consistency; (iv) error characteristics of the retrievals may be computed directly as a function of surface reflectance measurement error characteristics and sensor characteristics (signal to noise, calibration and band selection) (v) BIOPHYS/Landsat provides an explicit, physical structural framework, and, perhaps most significantly:(vi) it produces continuous fields of the parameters required for carbon, water and energy cycling models. To demonstrate the robustness of BIOPHYS/Landsat we produce and validate biophysical parameter fields from four spatially contiguous Landsat scenes, calibrated and corrected for molecular, water vapor and aerosols by the LEDAPS project (Masek et al, in press) collected over a decadal period. We compare our derived biophysical parameter values to ground observations and show how error characteristics depend on the number of solar illumination angles available for parameter extraction.
DE: 0400 BIOGEOSCIENCES
DE: 0439 Ecosystems, structure and dynamics (4815)
DE: 0480 Remote sensing
SC: Biogeosciences [B]
MN: Fall Meeting 2005