Helen Cleugh and Eva van Gorsel Near-real-time measurement of CO 2 , water and energy fluxes: Determining the best available estimates of continental carbon and water fluxes
Dec 24, 2014
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
“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
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
Logo
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
ETQ
Logo
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
OzFlux Data Path
OzFluxQC/post-processing
time scales involved in the land – air exchanges of carbon and water
after M.Williams et al., www biogesciences.net/t/1341/2009/
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
time and length scales covered
Courtesy P. Isaac
Seconds
Minutes
Tim
e
Scale
10-3 10-2 10-1 100 101 102
103
104metres
Length Scale
10-1
100
101
102
103
104
105
106
Leaf Canopy
Patch Region
Days
Yearsseconds
Leaf LevelObservations
Flu
x To
wer
Aircraft Fluxes
Aircraft Remote Sensing
Satellite Remote Sensing
Land Surface Model
GCM
Plot LevelObservations
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.
Modelling Framework BIOS2
Observations for BIOS2 constraints and evaluation
Viney-Vaze unimpaired catchments
OzFlux sitesInventory sites (Injune, Kioloa)Above-ground phytomass (VAST+Raison+Hilbert)Above-ground litter (VAST)Litter-fall (VAST)Soil carbon (VAST)
Multiple constraints on Australian terrestrial Net Primary Production: Eddy flux data provide the tightest constraint
error bars = uncertainty from propagated parameter uncertainties (1s)
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
A reality check - comparing OzFlux measured ET, GPP and BIOS2 simulations
Monthly
Monthly
Annual
Annual
BIOS2 evaluation: comparison with Viscarra Rossel observation-based soil carbon
Aust
ralia
n CO
2 Bud
get
Haverd et al. 2013 a, b. Biogeosciences
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
OzFlux 2013Sites 28
Accounts 96Site-years 62
11 years of ecosystem breathing at Tumbarumba, NSW
Thank
You and
Ques
tions
AcknowledgementsTERN HQ
• Tim, Stuart, Guru and the teamOzFlux
• Ray Leuning – Founding OzFlux Director• OzFlux Steering Committee: Mike Liddell,
Lindsay Hutley, Jason Beringer, Wayne Meyer, Alex Held, Peter Isaac
• OzFlux PIsCollaborators
• Vanessa Haverd• FluxNet
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
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)
OzFluxAnd TERN
Australian ecosystem and climate science
3. Connections: Global
FLUXNET
GEWEX Future Earth: WCRP - ESSP
NEON
OzFluxAnd TERN
Global ecosystem, climate and Earth system science
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”
…. the TERN infrastructure “ecosystem”
Knowledge of ecosystem exchange of carbon, water &
energy
Vegetation typeGPP
Veg indices (NDVI, EVI)Leaf area index
FireCanopy properties .....
CO2 and H2O FluxesRadiation
Meteorology
Site characteristicsBiomass
Soil carbon & nutrients
Leaf-level photosynthesis
Data assimilation and integration into modelling applications
AusPlots and Australian Supersites Network
OzFlux Network
eMASTAusCover
abstractThe 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.