Abstract
The National Aeronautics and Space Administration's Soil Moisture Active Passive (SMAP) mission Level 4 Carbon (L4C) product provides model estimates of the Net Ecosystem CO2 exchange (NEE) incorporating SMAP soil moisture information. The L4C product includes NEE, computed as total ecosystem respiration less gross photosynthesis, at a daily time step posted to a 9-km global grid by plant functional type. Component carbon fluxes, surface soil organic carbon stocks, underlying environmental constraints, and detailed uncertainty metrics are also included. The L4C model is driven by the SMAP Level 4 Soil Moisture data assimilation product, with additional inputs from the Goddard Earth Observing System, Version 5 weather analysis, and Moderate Resolution Imaging Spectroradiometer satellite vegetation data. The L4C data record extends from March 31, 2015 to present with ongoing production and 8-12 day latency. Comparisons against concurrent global CO2 eddy flux tower measurements, satellite solar-induced canopy florescence, and other independent observation benchmarks show favorable L4C performance and accuracy, capturing the dynamic biosphere response to recent weather anomalies. Model experiments and L4C spatiotemporal variability were analyzed to understand the independent value of soil moisture and SMAP observations relative to other sources of input information. This analysis highlights the potential for microwave observations to inform models where soil moisture strongly controls land CO2 flux variability; however, skill improvement relative to flux towers is not yet discernable within the relatively short validation period. These results indicate that SMAP provides a unique and promising capability for monitoring the linked global terrestrial water and carbon cycles.
| Original language | English |
|---|---|
| Article number | 8008865 |
| Pages (from-to) | 6517-6532 |
| Number of pages | 16 |
| Journal | IEEE Transactions on Geoscience and Remote Sensing |
| Volume | 55 |
| Issue number | 11 |
| DOIs | |
| State | Published - Nov 2017 |
Funding
Computational resources were provided by the NASA High-End Computing Program through the NASA Center for Climate Simulation. The authors would like to thank the SMAP L4C Calibration and Validation flux tower partners and La Thuile synthesis site investigators for the contribution of flux tower data. They would like to thank the SMAP L4C Cal/Val partners who contributed data but did not co-author: M. Aurela (Finnish Meteorological Institute, Helsinki, Finland), D. Baldocchi (University of California, Berkley, CA, USA), J. Beringer (University of Western Australia, Crawley WA, Australia), W. Oechel (San Diego State University, San Diego, CA, USA), and H. Wheater (University of Saskatchewan, Saskatoon, SK, Canada). The La Thuile synthesis data set includes eddy covariance data acquired by the FLUXNET community and in particular by the following networks: AmeriFlux (U.S. Department of Energy, Biological and Environmental Research, Terrestrial Carbon Program (DE-FG02-04ER63917 and DE-FG02-04ER63911), AfriFlux, AsiaFlux, CarboAfrica, CarboEuropeIP, CarboItaly, Car-boMont, ChinaFlux, Fluxnet-Canada (supported by CFCAS, NSERC, BIOCAP, Environment Canada, and NRCan), Green-Grass, KoFlux, LBA, NECC, OzFlux, TCOS-Siberia, and USCCC. They would also like to thank CarboEuropeIP, FAO-GTOS-TCO, iLEAPS, the Max Planck Institute for Biogeochemistry, National Science Foundation, the University of Tuscia, the Université Laval, Environment Canada, and the U.S. Department of Energy, for the financial support to the eddy covariance data harmonization, and the Berkeley Water Center, the Lawrence Berkeley National Laboratory, Microsoft Research eScience, the Oak Ridge National Laboratory, the University of California, Berkeley, and the University of Virginia, for the database development and technical support, OzFlux and the Australia Terrestrial Ecosystem Research Network (http://www.tern.org.au) for the support with collection and archiving of Australian flux data, and D. Baldocchi and J. Beringer for their comments and discussions which helped improve this manuscript.
| Funders | Funder number |
|---|---|
| 1636476, 1503912 | |
| Biological and Environmental Research | DE-FG02-04ER63911, DE-FG02-04ER63917 |
| Oak Ridge National Laboratory | |
| Lawrence Berkeley National Laboratory | |
| University of California at Berkeley | |
| Université Laval | |
| Natural Resources Canada | |
Keywords
- CO fluxes
- Soil Moisture Active Passive (SMAP) Mission
- carbon cycle
- ecosystems
- environmental monitoring
- microwave remote sensing
- soil moisture
- vegetation
- water cycle
