Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint...
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Transcript of Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint...
![Page 1: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/1.jpg)
Eddy correlation quick-course
1. Background
2. Raw signals • Time series• covariantie• Spectra• Footprint
3. Data processing• angle of attack dependent calibration• detrending• rotation• Frequency response corrections • Schotanus • Webb
![Page 2: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/2.jpg)
Background of Eddy correlation
1. We want to measure the fluxes of sensible heat, latent heat (evaporation), carbon dioxide and methane
2. To measure them, we use the turbulent properties of the air
3. For example: during the day:
temperature humidity CO2
high colder drier normal4 m 24 oC 17 g/kg 360 ppm
low warmer moister depleted0.1 m 25 oC 18 g/kg 355 ppm
![Page 3: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/3.jpg)
Background of Eddy correlation
CO2
360 ppm
U
CO2
355 ppm CO2
355 ppm CO2
360 ppm
U
I II
25 °C
18 g/kg H2O
355 ppm CO2
25 °C
18 g/kg H2O
355 ppm CO2
24 °C
17 g/kg H2O
360 ppm CO217 g/kg
360 ppm
24 °C
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Measurements at the Horstermeer
![Page 5: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/5.jpg)
The raw signals
![Page 6: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/6.jpg)
The raw signals
![Page 7: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/7.jpg)
correlation w - T
r = 0.55
r2 = 0.30
![Page 8: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/8.jpg)
covariance
covariance = (w – wmean) x (T – Tmean)
or:
when defining
w’ = (w – wmean)
T’ = (T – Tmean)
then
covariance = w’T’
![Page 9: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/9.jpg)
covariance
w’T’ = 0.33 m/s K
to calculate the energy content of this air stream we are actually interested in the covariance of
H = w’ (ρ Cp T)’ = (ρ– ρmean) Cp w’ T’
with ρ ~ 1.2 kg/m3 the air density and Cp ~ 1004.67 J/kg the heat capacity of air
But (fortunately) ρ does not correlate with w’T’, thus:
H = ρ Cp w’T’ = 1.2 * 1005 * 0.33 = 397 W/m2
![Page 10: Eddy correlation quick-course 1.Background 2.Raw signals Time series covariantie Spectra Footprint 3.Data processing angle of attack dependent calibration.](https://reader035.fdocuments.us/reader035/viewer/2022070415/56649e795503460f94b78d28/html5/thumbnails/10.jpg)
covarianceH = ρ Cp w’T’
Similarly:
LE = λ w’ρv’ = ρ λ w’q’
fco2 = w’ρco2’
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Angle of Attack Dependent Calibration
Gash and Dolman, 2003van der Molen, Gash and Elbers, 2004
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Detrending
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Other corrections
rotationFrequency response corrections Schotanus
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Webb corrections
rotationFrequency response corrections Schotanus Webb