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Direct Satellite Inference of Ecosystem Light Use Efficiency for Carbon Exchange using MODIS on Terra and Aqua
Project Funding: 2004 - 2007
NRA: 2004 NASA: Carbon Cycle Science
Funded by NASA
Abstract:We propose to develop a methodology using Moderate-Resolution Spectroradiometer (MODIS) satellite data to improve estimates of gross ecosystem productivity (GEP) of terrestrial biomes. GEP is related to the product of three terms: the incident Photosynthetically Active Radiation (PARi), the fraction of Absorbed Photosynthetically Active Radiation (fAPAR), and the photosynthetic Light Use Efficiency (LUE). Optimal photosynthetic functionality is negatively affected by environmental stress factors that cause down-regulation (i.e., reduced rate of photosynthesis or lowered LUE). LUE is a scaler indicator of the photosynthetic down-regulation associated with diurnal and seasonal vegetation stress responses. The current MODIS gross primary productivity (GPP) product is based on a 1-km spatial resolution averaged over an 8-day time period, and utilizes a biome-specific look-up table value of LUE modified by modeled values for PAR, daily minimum air temperature and vapor pressure deficit (VPD) to produce a scaler value (0-1) for LUE. We propose to directly determine photosynthetic down-regulation through measurement of vegetation spectral reflectance changes obtained by satellite. The reflective land and ocean MODIS bands will be used to directly estimate fAPAR and LUE, the latter by monitoring vegetation stress responses exhibited by photosynthetic pigments (e.g., xanthophyll cycle and chlorophyll status), a process that will utilize visible spectral bands previously devoted to ocean productivity studies. For MODIS data acquired over selected flux towers in the Fluxnet-Canada Network, we will create daily (or twice daily) instantaneous LUE and daily GEP estimates using morning (Terra) and afternoon (Aqua) MODIS swath observations. MODIS-derived LUE and GEP will be compared with tower-based estimates of GPP and LUE (gC MJ-1 PAR) made from CO2 fluxes and PAR measurements. MODIS estimates of the surface Bi-Directional Reflectance Distribution Function (BRDF) will be used to correct the morning vs. afternoon and nadir/off-nadir Terra and Aqua data to a standard viewing geometry. The MODIS-derived LUE will be compared with in situ LUE at the flux tower sites, and the relationships evaluated across ecosystems or biomes, for data available between 2000 and 2005.
Publications:
Drolet, G. G., Huemmrich, K. F., Hall, F. G., Middleton, E. M., Black, T. A., Barr, A. G., Margolis, H. A. 2005. A MODIS-derived photochemical reflectance index to detect inter-annual variations in the photosynthetic light-use efficiency of a boreal deciduous forest. Remote Sensing of Environment. 98(2-3), 212-224. DOI: 10.1016/j.rse.2005.07.006
Huemmrich, K.F., Middleton, E.M., Drolet, G., Hall, F.G., Margolis, H., and Knox, R.G. 2005. Determining ecosystem light use efficiency for carbon exchange from satellite, in Optical Sensors and Sensing Systems for Natural Resources and Food Safety and Quality, edited by Yud-Ren Chen, George E. Meyer, Shu-I Tu, Proc. of SPIE Vol. 5996, 599605,
Middleton, E., Drolet, G., Huemmrich, K., Hall, F., Knox, R., Black, A., Barr, A., Lyapustin, A., Gervin, J., and Margolis, H., Direct Satellite Inference of Ecosystem Light Use Efficiency for Carbon Exchange Using MODIS on Terra and Aqua, Proceedings of International Geosciences and Remote Sensing Symposium (IGARSS) 2004, Anchorage, AK, 20-26 September 2004
2008 NASA Carbon Cycle & Ecosystems Joint Science Workshop Posters
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