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A satellite‐based biosphere parameterization for net ecosystem CO 2 exchange: Vegetation Photosynthesis and Respiration Model (VPRM)
Author(s) -
Mahadevan Pathmathevan,
Wofsy Steven C.,
Matross Daniel M.,
Xiao Xiangming,
Dunn Allison L.,
Lin John C.,
Gerbig Christoph,
Munger J. William,
Chow Victoria Y.,
Gottlieb Elaine W.
Publication year - 2008
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2006gb002735
Subject(s) - eddy covariance , environmental science , fluxnet , enhanced vegetation index , photosynthetically active radiation , ecosystem respiration , leaf area index , moderate resolution imaging spectroradiometer , biome , biosphere , vegetation (pathology) , atmospheric sciences , primary production , ecosystem , remote sensing , normalized difference vegetation index , satellite , photosynthesis , ecology , geography , vegetation index , chemistry , geology , physics , medicine , biochemistry , pathology , astronomy , biology
We present the Vegetation Photosynthesis and Respiration Model (VPRM), a satellite‐based assimilation scheme that estimates hourly values of Net Ecosystem Exchange (NEE) of CO 2 for 12 North American biomes using the Enhanced Vegetation Index (EVI) and Land Surface Water Index (LSWI), derived from reflectance data of the Moderate Resolution Imaging Spectroradiometer (MODIS), plus high‐resolution data for sunlight and air temperature. The motivation is to provide reliable, fine‐grained first‐guess fields of surface CO 2 fluxes for application in inverse models at continental and smaller scales. An extremely simple mathematical structure, with minimal numbers of parameters, facilitates optimization using in situ data, with finesse provided by maximal infusion of observed NEE and environmental data from networks of eddy covariance towers across North America (AmeriFlux and Fluxnet Canada). Cross validation showed that the VPRM has strong prediction ability for hourly to monthly timescales for sites with similar vegetation. The VPRM also provides consistent partitioning of NEE into Gross Ecosystem Exchange (GEE, the light‐dependent part of NEE) and ecosystem respiration ( R , the light‐independent part), half‐saturation irradiance of ecosystem photosynthesis, and annual sum of NEE at all eddy flux sites for which it is optimized. The capability to provide reliable patterns of surface flux for fine‐scale inversions is presently limited by the number of vegetation classes for which NEE can be constrained by the current network of eddy flux sites and by the accuracy of MODIS data and data for sunlight.