Scintillometer and eddy covariance comparisons over sagebrush and invasive cheatgrass communities in Idaho EPSCoR Project Suported by NSF

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Scintillometer and eddy covariance comparisons
over sagebrush and invasive cheatgrass
communities in IdahoEPSCoR Project Suported by
NSF
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Authors

• University of Idaho
• Wenguang Zhao, Rick Allen, Clarence Robison,
  Jeppe Kjaersgaard, Ricardo Trezza, Aureo
  Oliveira, Ramesh Dhungel
• Idaho State University
• Matt Germino
• Boise State University
• Venkat Sridhar
• Wageningen University
• Henk de Bruin

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Background

• 1. Sensible heat flux (H) is an important energy
  dissipation in surface energy balances and
  evapotranspiration (ET) studies.
• 2. Representation of H and ET measured by
  traditional methods (EC and BR etc) is limited,
  especially for heterogeneous fields.
• 3. Large aperture scintillometry (LAS) is an
  alternative method to estimate H from a
  relatively large footprint (source) area.

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Questions

• 1. How can we accurately calculate H from the
  LAS measurement, structure function constant of
  refractive index fluctuations for the wavelength
  used by the LAS?
• 2. How does the H calculated by the LAS
  measurement compare to the traditional EC
  measurement result?

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Experiment sites
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Instrumentation
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Hollister Site Sagebrush
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LAS Transmitter
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LAS Receiver
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Eddy Covariance Site 1
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Eddy Covariance system
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Radiation System
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Soil Sensors
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Raft River Site Cheatgrass
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LAS Transmitter A Receiver B
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Eddy Covariance Site 1
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Macks Inn Site Alpine forest (south tower)
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Macks Inn Site Alpine forest (north tower)
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Results and Discussions
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LAS data (Cn2) ? H

• Four scenarios were used to calculate H from Cn2
  
• Scenario 1
• Ta, u and L from CSAT3 (RM Young) ET used in
  the Bowen Ratio correction for the LAS was from
  the EC.
• Calculate Ft, T and H directly.
• Scenario 2
• Ta and u from CSAT3 (RM Young) ET used in the
  Bowen Ratio correction for the LAS was from EC.
• Calculate L, Ft, T and H iteratively.

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LAS data (Cn2) ? H

• Four scenarios were used to calculate H from Cn2
  
• Scenario 3
• Ta and u from CSAT3 (RM Young ET used in the
  Bowen Ratio correction for the LAS was from EC.
• Calculate u, L, Ft, T and H using TCLI method.
• Scenario 4
• Measured Rn (NR01), G (HFT), Ta (HMP) and P
  (PTB110) u from CSAT3 (RM Young).
• Calculate u, L, Ft, T, H and ET iteratively
  (three-concentric-loop-iterative method). ---
  note this is the most generally used method.

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Conclusions

• 1. Good agreement was obtained between H
  measured by CSAT3 and RM Young 81000 3-D sonic
  anemometers
• 2. H measured by Scintec BLS900 compared well
  with both EC systems (CSAT3 and RM Young).
• Thank you!

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Questions?