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Near real-time measurement of CO2, water and energy fluxes: determining the best available estimates of continental carbon and water fluxes_Cleugh


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Near real-time measurement of CO2, water and energy fluxes: determining the best available estimates of continental carbon and water fluxes_Cleugh

  1. 1. Helen Cleugh and Eva van Gorsel Near-real-time measurement of CO2, water and energy fluxes: Determining the best available estimates of continental carbon and water fluxes
  2. 2. “Today, a new scientific revolution is emerging [...] where groups of scientists are producing global scale information on carbon and water fluxes. They are doing so by merging of information from networks of flux towers, biophysical models, ecological databases and satellite-based remote sensing to produce a new generation of flux maps.” Dennis Baldocchi, UC Berkeley
  3. 3. Why are we interested in fluxes? Globally terrestrial ecosystems annually sequester about one quarter of anthropogenic emissions of CO2  They provide an ecosystem service worth millions of dollars In sequestering carbon they also use water. Water use by vegetation (through evapotranspiration) is the biggest loss term in the terrestrial water budget  Through land management, evapotranspiration is the only term in the water budget that we can manage Terrestrial landscapes also affect the local and regional climate through changing the surface properties of reflectance and roughness Quantifying the exchanges of carbon, water and energy in space and time provides critical information required to underpin the sound management of Australia’s landscapes and the ecosystem services they provide
  4. 4. Purpose is to measure ecosystem fluxes CO2 and water vapour using eddy covariance method - Water ( E, ET) and CO2 (NEE) Energy - Radiation (Q) and heat (H, G) Above canopy; spatially-averaged Continuous: hourly to multi-annual OzFlux infrastructure and processes A continental network of flux stations NEE ET H Q G ET Q
  5. 5. Drivers: • Above-canopy meteorology • Soil temperature and moisture Data for analysis & interpretation: • Within-canopy temperature, CO2, humidity and wind profiles Purpose is to measure ecosystem fluxes and … OzFlux infrastructure and processes A continental network of flux stations Flux towers measuring vineyard and forest CO2 and water fluxes
  6. 6. OzFlux Data Path OzFlux QC/post-processing
  7. 7. time scales involved in the land – air exchanges of carbon and water after M.Williams et al., www
  8. 8. spatial scales involved... ... span about 14 orders of magnitude after D. Baldocchi, 5th annual flux course, 'Biosphere Breathing' Chloroplast: 10-6 m Stomata: 10-5 m Plant: 1-100 m Leaf: 0.01-0.1 m Canopy: 100-1000 m Globe: 10'000 km Landscape: 1-100 km Continent: 1000 km
  9. 9. time and length scales covered Courtesy P. Isaac Seconds Minutes TimeScale 10-3 10-2 10-1 100 101 102 103 104 metres Length Scale 10-1 100 101 102 103 104 105 106 Leaf Canopy Patch Region Days Years seconds Leaf Level Observations Flux Tower Aircraft Fluxes Aircraft Remote Sensing Satellite Remote Sensing Land Surface Model GCM Plot Level Observations Leaf Level Physiology assumed to apply Direct measurement Indirect measurement (remote sensing) Modelling Remote sensing observations are rich in spatial information content and can be used to ‘scale up’ from local to larger scales Tower observations provide information on ecosystem processes for the exchanges of energy, water and carbon on all relevant time scales. Scaling up through modelling allows quantification through space and time and physical understanding.
  10. 10. Modelling Framework BIOS2
  11. 11. Observations for BIOS2 constraints and evaluation
  12. 12. Multiple constraints on Australian terrestrial Net Primary Production: Eddy flux data provide the tightest constraint error bars = uncertainty from propagated parameter uncertainties (1 ) NPP (GtC y -1 ) 0 1 2 3 4 Eddy fluxes + Litterfall + Streamflow Streamflow + Eddy fluxes Streamflow + Litterfall Eddy fluxes + Litterfall Litterfall Streamflow Eddy fluxes Prior estimate
  13. 13. A reality check - comparing OzFlux measured ET, GPP and BIOS2 simulations Monthly Monthly Annual Annual
  14. 14. BIOS2 evaluation: comparison with Viscarra Rossel observation-based soil carbon
  15. 15. AustralianCO2Budget Haverd et al. 2013 a, b. Biogeosciences
  16. 16. Concluding comments: carbon and water budgets at ecosystem to continental scales OzFlux data have been used to: • Test and improve the land surface model [CABLE] for Australian ecosystems • CABLE is part of Australia’s newly developed global climate model [ACCESS] • Significantly reduce the uncertainty in estimated NPP for Australia, using CABLE as part of BIOS2 • Foundation for the first comprehensive carbon budget for Australia
  17. 17. OzFlux 2013 Sites 28 Accounts 96 Site-years 62 11 years of ecosystem breathing at Tumbarumba, NSW
  18. 18. Thank You and Questions Acknowledgements TERN HQ • Tim, Stuart, Guru and the team OzFlux • Ray Leuning – Founding OzFlux Director • OzFlux Steering Committee: Mike Liddell, Lindsay Hutley, Jason Beringer, Wayne Meyer, Alex Held, Peter Isaac • OzFlux PIs Collaborators • Vanessa Haverd • FluxNet
  19. 19. Concluding comments: carbon and water budgets at ecosystem to continental scales Insights into the carbon and water budgets for the Australian continent, e.g.: • Large inter-annual variability in NPP driven by variation in available moisture • Larger than anthropogenic greenhouse gas emissions
  20. 20. 3. Connections: Australia Regional carbon and water budgets (e.g. RECCAP) Australian Water Resources Assessments Australian Climate Change Science Program Climate and Earth System Modelling (ACCESS) OzFlux And TERN Australian ecosystem and climate science
  21. 21. 3. Connections: Global FLUXNET GEWEX Future Earth: WCRP - ESSP NEON OzFlux And TERN Global ecosystem, climate and Earth system science
  22. 22. A capability to determine carbon and water budgets at ecosystem to continental scales • Uptake and release of CO2 and other GHG [fluxes] • Carbon stocks in soil, plants and air [stores] • Water and carbon • Measurements and models …. the TERN infrastructure “ecosystem”
  23. 23. …. the TERN infrastructure “ecosystem” Knowledge of ecosystem exchange of carbon, water & energy Vegetation type GPP Veg indices (NDVI, EVI) Leaf area index Fire Canopy properties ..... CO2 and H2O Fluxes Radiation Meteorology Site characteristics Biomass Soil carbon & nutrients Leaf-level photosynthesis Data assimilation and integration into modelling applications AusPlots and Australian Supersites Network OzFlux Network eMASTAusCover
  24. 24. abstract The role played by natural land and ocean sinks in sequestering greenhouse gas (GHG) emissions, and the trajectory of these sinks into the future, is critically important information needed to underpin climate mitigation and adaption policies. Providing this information requires carbon cycle observations that track the uptake and release of greenhouse gases in land, air and oceans over long periods so that effects of a varying and changing climate, along with land management, can be captured. Climate models need to adequately represent ecosystems and ecosystem processes to provide credible and useful future scenarios. We also need information on how land can be managed to maximise carbon uptake and thus mitigate GHG emissions, including the effect of elevated carbon dioxide levels on plants. This talk will describe the capability needed to determine carbon and water budgets at ecosystem to continental scales – much of which has been developed by TERN, the Terrestrial Ecosystem Research Network. The talk will then focus on the important role that OzFlux plays through directly measuring the exchanges of energy, water and CO2 and the use of these measurements in determining carbon, GHG and water budgets and therefore answering these critical questions.