Project Funding: 2011 - 2014

NRA: 2009 NASA: The Science of Terra and Aqua   

Funded by NASA

Abstract:
LAI and FPAR products have a large user base in the Earth science community. These products are available from the Terra/Aqua MODIS and Terra MISR sensors and are being generated using similar retrieval technique that ensures their consistency. The largest, most obvious weakness of the MISR product compared to its MODIS counterpart is its low temporal resolution. In studies that require high temporal resolution data, e.g., determining the onset of greenness, the use of MODIS land surface products is the preferred option. The strength of MISR observing strategy is its ability to provide a set of canopy structural parameters that the MODIS approach does not have. This set includes spectrally invariant parameters - the recollision and directional escape probabilities. They are sensitive to horizontal structural variables such as tree crown geometry, tree density, within crown foliage density and forest composition. The parameters specify an accurate relationship between spectral response of vegetation canopy to incident solar radiation at the leaf and canopy scale. The spectral invariants therefore can be used to remove the effect of 3D canopy structure from hyperspectral surface reflectances and provide an accurate estimate of leaf spectral properties (leaf albedo). The spectrally varying leaf albedo in combination with structurally varying recollision and escape probabilities offer a powerful means to quantify changes in leaf physiology. The leaf level physiological processes are among the climate variables that most directly control the dynamics of terrestrial ecosystem processes. Availability of this information will also improve the prediction capacity of existing models of biogeochemistry and ecology as it allows the relaxation of a number of assumptions about unresolved small scale variability that underlie many of them. The MISR LAI/FPAR operational algorithm is based on the theory of spectral invariants and thus provides the required framework for the synergy of multiangle and hyperspectral data. The primary objective of the proposed research is to demonstrate the feasibility of simultaneously retrieving spectral invariants (recollision and escape probabilities) and optical properties of a mean leaf over satellite pixel from hyperspectral and multiangle data and relate these parameters to dominant tree species and leaf biochemical constituents. The core research tasks to be performed include (i) refinements to the MISR LAI/FPAR algorithm to ensure reliably retrieval of the spectral invariants and leaf albedo from synergistic analysis of multi-angle and hyperspectral data; (ii) generation of the canopy spectral invariants, leaf spectra, species distribution, LAI and FPAR at 275 m resolution over the EOS Core Validation sites at Boston University computing facilities and their validation; (iii) evaluation of the reliability of the data set to capture alternations in leaf physiology through changes in the leaf optics and canopy structure. This data product will complement Collection 6 MODIS LAI/FPAR product at 500 m resolution, which is currently under development.

2013 NASA Terrestrial Ecology Science Team Meeting Poster(s)

• Monitoring canopy structure and leaf biochemistry using multiangle and hyperspectral data   --   (Yuri Knyazikhin, Philip Lewis, Mathias Disney, Pauline Stenberg, Matti Mottus, Yan Yang, Miina Rautiainen, Mitchell Schull, Ranga Babu Myneni)   [abstract]   [poster]

2011 NASA Carbon Cycle & Ecosystems Joint Science Workshop Poster(s)

• Uncertainties in the Relationship Between Hyperspectral Data and Leaf Nitrogen Content   --   (Yuri Knyazikhin, Mitchell Schull, Ranga Babu Myneni, Robert Kaufmann)   [abstract]   [poster]

More details may be found in the following project profile(s):

• NASA Terrestrial Ecology (TE) Project Profile