Dennis Baldocchi University of California, Berkeley JASON GHG Emissions Monitoring Summer Study (June 16-18, 2010) La Jolla, CA Micrometeorological Methods Used to Measure Greenhouse Gas Fluxes: The Challenges Associated with Them, at the Local to Global Scales
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Dennis Baldocchi University of California, Berkeley JASON GHG Emissions Monitoring
Micrometeorological Methods Used to Measure Greenhouse Gas Fluxes: The Challenges Associated with Them, at the Local to Global Scales. Dennis Baldocchi University of California, Berkeley JASON GHG Emissions Monitoring Summer Study (June 16-18, 2010) La Jolla, CA. - PowerPoint PPT Presentation
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Dennis BaldocchiUniversity of California, Berkeley
JASON GHG Emissions Monitoring Summer Study (June 16-18, 2010)
La Jolla, CA
Micrometeorological Methods Used to Measure Greenhouse Gas Fluxes:
The Challenges Associated with Them, at the Local to Global Scales
Methods To Assess Terrestrial Carbon Budgets at Landscape to Continental Scales, and Across
LI-7700 Methane Sensor, variant of frequency modulation spectroscopy
Open path, 0.5 mShort optical path length, 30 mLow Power Use: 8 W, no pumpModerate Noise: 5 ppb at 10 HzStable Calibration
ESPM 228 Adv Topics Micromet & Biomet
0
)('' dSww ww
0
)('' dScwF wc
Co-Spectrum
Power Spectrum defines the Frequencies to be Sampled
Power Spectrum
ESPM 228 Adv Topics Micromet & Biomet
Signal Attenuation:The Role of Filtering Functions and Spectra
• High and Low-pass filtering via Mean Removal– Sampling Rate (1-10Hz) and Averaging Duration (30-60 min)
• Digital sampling and Aliasing• Sensor response time• Sensor Attenuation of signal
– Tubing length and Volumetric Flow Rate– Sensor Line or Volume averaging
• Sensor separation– Lag and Lead times between w and c
M.Detto and D. Baldocchi
Comparing Co-spectra of open-path CO2 & H2O sensor and closed-path CH4 sensor
Co-Spectra are More Forgiving of Inadequate Sensor Performance than Power SpectraBecause there is little w-c correlation in the inertial subrange
Co-Spectra is a Function of Atmospheric Stability:Shifts to Shorter Wavelengths under Stable ConditionsShifts to Longer Wavelengths under Unstable Conditions
Detto, Baldocchi and Katul, Boundary Layer Meteorology, accepted
ESPM 228 Adv Topics Micromet & Biomet
Zero-Flux Detection Limit, Detecting Signal from Noise
' ' wc w cF w c r rwc ~ 0.5ch4 ~ 0.84 ppbco2 ~ 0.11 ppm
Methane Lab Calibration
Time
260 280 300 320 340 360 380 400
Met
hane
Sen
sor
1880
1890
1900
1910
1920
Mean: 1897.4277StdDev: 0.8411Std Err 0.0219
U* w Fmin, CH4 Fmin, CO2m/s m/s nmol m-2 s-1 mmol m-2 s-1
Ground Based, Time Series of Hyper-Spectral Reflectance Measurements, in Conjunction with Flux Measurements Can be Used to Design Future Satellites
Remote Sensing of NPP:Up and down PAR, LED, Pyranometer, 4 band Net Radiometer
LED-based sensors are Cheap, Easy to Replicate and Can be Designed for a Number of Spectral Bands
Spectrally-Selective Vegetation Indices Track Seasonality of C Fluxes Well
Ryu et al. Agricultural and Forest Meteorology, in review
Ryu et al. Agricultural and Forest Meteorology, in review
Vegetation Indices can be Used to Predict GPP with Light Use Efficiency Models
UpScaling of FluxNetworks
Xiao et al 2010, Global Change Biology
What We can Do:Is Precision Good Enough for Treaties?
Xiao et al 2010, Global Change Biology
Map of Gross Primary Productivity Derived from Regression Tree AlgorithmsDerived from Flux Network, Satellite Remote Sensing and Climate Data
Xiao et al 2010, Global Change Biology
Net Ecosystem C Exchange
Xiao et al. 2008, AgForMet
springsummer
autumn winter
Jingfeng Xiao and D Baldocchi
area-averaged fluxes of NEE and GPP were -150 and 932 gC m-2 y-1
net and gross carbon fluxes equal -8.6 and 53.8 TgC y-1
Upscale GPP and NEE to the Biome Scale
Take-Home Message for Application of Eddy Covariance Method under Non-Ideal
Conditions
•Routine Flux Measurements Must Comply with Governing Principles of Conservation Equation•Design Experiment that measures Flux Divergence and Storage, in addition to Covariance•Networks need more Sites in Tropics and Distinguish C3/C4 crops•Networks need Sites that Cover a Range of Disturbance History•Network of Flux Towers, in conjunction with Remote Sensing, Climate Networks and Machine Learning Algorithms has Potential to Produce Carbon Flux Maps for Carbon Monitoring for Treaty, with Caveats and Accepted Errors
Additional Background Material
Sampling Error with Two Towers
Hollinger et al GCB, 2004
Moffat et al., 2007, AgForMet
Gap-Filling Inter-comparison Bias Errors
ESPM 228 Adv Topic Micromet & Biomet
Moffat et al., 2007, AgForMet
ESPM 228 Adv Topic Micromet & Biomet
Root Mean Square Errors with Different Gap Filling Methods