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Integrating Chlorophyll fapar and Nadir Photochemical Reflectance Index from EO-1/Hyperion to Predict Cornfield Daily Gross Primary ProductionThe concept of light use efficiency (Epsilon) and the concept of fraction of photosynthetically active ration (PAR) absorbed for vegetation photosynthesis (PSN), i.e., fAPAR (sub PSN), have been widely utilized to estimate vegetation gross primary productivity (GPP). It has been demonstrated that the photochemical reflectance index (PRI) is empirically related to ε. An experimental US Department of Agriculture (USDA) cornfield in Maryland was selected as our study field. We explored the potential of integrating fAPAR(sub chl) (defined as the fraction of PAR absorbed by chlorophyll) and nadir PRI (PRI(sub nadir)) to predict cornfield daily GPP. We acquired nadir or near-nadir EO-1/Hyperion satellite images that covered the cornfield and took nadir in-situ field spectral measurements. Those data were used to derive the PRI(sub nadir) and fAPAR (sub chl). The fAPAR (sub chl) is retrieved with the advanced radiative transfer model PROSAIL2 and the Metropolis approach, a type of Markov Chain Monte Carlo (MCMC) estimation procedure. We define chlorophyll light use efficiency Epsilon (sub chl) as the ratio of vegetation GPP as measured by eddy covariance techniques to PAR absorbed by chlorophyll (Epsilon(sub chl) = GPP/APAR (sub chl). Daily Epsilon (sub chl) retrieved with the EO-1 Hyperion images was regressed with a linear equation of PRI (sub nadir) Epsilon (sub chl) = Alpha × PRI (sub nadir) + Beta). The satellite Epsilon(sub chl- PRI (sub nadir) linear relationship for the cornfield was implemented to develop an integrated daily GPP model [GPP = (Alpha × PRI(sub nadir) + Beta) × fAPAR (sub chl) × PAR], which was evaluated with fAPAR (sub chl) and PRI (sub nadir) retrieved from field measurements. Daily GPP estimated with this fAPAR (sub chl-) PRI (nadir) integration model was strongly correlated with the observed tower in-situ daily GPP (R(sup 2) = 0.93); with a root mean square error (RMSE) of 1.71 g C mol−(sup -1) PPFD and coefficient of variation (CV) of 16.57%. Both seasonal Epsilon (sub chl) and PRI (sub nadir) were strongly correlated with fAPAR (sub chl ) retrieved from field measurements, which indicates that chlorophyll content strongly affects seasonal epsilon (sub chl) and PRI (sub nadir). We demonstrate the potential capacity to monitor GPP with space-based visible through shortwave infrared (VSWIR) imaging spectrometers such as NASA's soon to be decommissioned EO- 1/Hyperion and the future Hyperspectral Infrared Imager (HyspIRI).
Document ID
Document Type
Reprint (Version printed in journal)
Zhang, Qingyuan (Universities Space Research Association Columbia, MD, United States)
Middleton, Elizabeth M. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Cheng, Yen-Ben (Sigma Space Corp. Lanham, MD, United States)
Huemmrich, K. Fred (Maryland Univ. Baltimore County Baltimore, MD, United States)
Cook, Bruce D. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Corp, Lawrence A. (Science Systems and Applications, Inc. Greenbelt, MD, United States)
Kustas, William P. (Agricultural Research Service Beltsville, MD, United States)
Russ, Andrew L. (Agricultural Research Service Beltsville, MD, United States)
Prueger, John H. (Agricultural Research Service Ames, IA, United States)
Yao, Tian (Universities Space Research Association Columbia, MD, United States)
Date Acquired
September 21, 2016
Publication Date
August 30, 2016
Publication Information
Publication: Remote Sensing of Environment
Volume: 186
ISSN: 0034-4257
Subject Category
Earth Resources and Remote Sensing
Report/Patent Number
Funding Number(s)
Distribution Limits
Daily GPP