Journal
REMOTE SENSING OF ENVIRONMENT
Volume 152, Issue -, Pages 375-391Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.rse.2014.06.022
Keywords
Fluorescence; Vegetation; Fluorescence; Chlorophyll; GOME-2; Gross primary productivity; Light-use efficiency; Flux tower; Growing season; Carbon uptake period; Phenology
Funding
- NASA Carbon Cycle Science program [NNH1ODA001N]
- U.S. Department of Energy, Biological and Environmental Research, Terrestrial Carbon Program [DEFG0204ER63917, DEFG0204ER63911]
- CFCAS
- NSERC
- BIOCAP
- Environment Canada
- NRCan
- CarboEuropeIP
- FAOGTOSTCO
- iLEAPS
- Max Planck Institute for Biogeochemistry
- National Science Foundation
- University of Tuscia
- Wageningen University CALM Group
- Universit Laval
- U.S. Department of Energy
- National Science Foundation (NSF)
- U.S. Department of Agriculture (USDA)
- U.S. Department of Energy (DOE)
- Biological and Environmental Research Program (BER)
- U.S. DOE, through the Midwestern Center of the National Institute for Global Environmental Change (NIGEC) [DE-FC03-90ER61010]
- BER [DE FG02-03ER63624, DE-FG03-01ER63278]
- NOAA [NA09OAR4310063]
- NASA [NNX10AR63G, NNX11A008A]
- NASA Terrestrial Ecology Program [NNX08AI77G]
- NSF Biocomplexity Program [EAR-0120630]
- Australian Research Council FT [FT1110602]
- [DP130101566]
- NASA [NNX10AR63G, 125421, NNX08AI77G, 100051] Funding Source: Federal RePORTER
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Mapping of terrestrial chlorophyll fluorescence from space has shown potential for providing global measurements related to gross primary productivity (GPP). In particular, space-based fluorescence may provide information on the length of the carbon uptake period. Here, for the first time we test the ability of satellite fluorescence retrievals to track seasonal cycle of photosynthesis as estimated from a diverse set of tower gas exchange measurements from around the world. The satellite fluorescence retrievals are obtained using new observations near the 740 nm emission feature from the Global Ozone Monitoring Experiment 2 (GOME-2) instrument offering the highest temporal and spatial resolution of available global measurements. Because GOME-2 has a large ground footprint (similar to 40 x 80 km(2)) as compared with that of the flux towers and the GOME-2 data require averaging to reduce random errors, we additionally compare with seasonal cycles of upscaled GPP estimated from a machine learning approach averaged over the same temporal and spatial domain as the satellite data surrounding the tower locations. We also examine the seasonality of absorbed photosynthetically-active radiation (AFAR) estimated from satellite measurements. Finally, to assess whether global vegetation models may benefit from the satellite fluorescence retrievals through validation or additional constraints, we examine seasonal cycles of GPP as produced from an ensemble of vegetation models. Several of the data-driven models rely on satellite reflectance-based vegetation parameters to derive estimates of APAR that are used to compute GPP. For forested (especially deciduous broadleaf and mixed forests) and cropland sites, the GOME-2 fluorescence data track the spring onset and autumn shutoff of photosynthesis as delineated by the upscaled GPP estimates. In contrast the reflectance-based indicators and many of the models, particularly those driven by data, tend to overestimate the length of the photosynthetically-active period for these biomes. Satellite fluorescence measurements therefore show potential for improving the seasonal dependence of photosynthesis simulated by global models at similar spatial scales. (C) 2014 Elsevier Inc All rights reserved.
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