Ogive
Title
Some considerations about the
Application of ogive analysis for quality control and spectral correction of eddy covariance fluxes
Christof Ammann, Albrecht Neftel
Content
Content
Motivation for spectral/ogive analysis: methodological flux measurement problems at the Swiss CarboEurope grassland site Some basics about ogives Application examples: High-frequency damping/correction Analysis for intermittency/stationarity of turbulence Conclusions
Site region
Measurement Site near Oensingen
0
N
annual distribution of wind directions
Site plots/fetch
Experimental Plots
200
0
N
150 100
EC systems
local SN scale [m]
Hi
50
g
y wa h
0
-50
- aerodyn. measurement height: z = 0.7 –1.2 m - sensor separation (lateral): s = 16 cm
-100
-150
-200 -300
-250
-200
-150
-100
-50
0
50
100
local WE scale [m]
Site wind
Nocturnal Wind Conditions
50.0 10
CO2 flux windspeed
8
CO2 flux [umol/m2/s]
windspeed ca. 1m above ground (Jun-Oct 2002)
6 0.0 4
frequency of occurrence [rel. units]
daytime nighttime
2
-50.0 20.07.2002 00:00
20.07.2002 12:00
21.07.2002 00:00
21.07.2002 12:00
22.07.2002 00:00
22.07.2002 12:00
0 23.07.2002 00:00
0
1
2
3
4
5
6
7
wind speed [m/s]
windspeed [m/s]
Site motivation
Motivation for spectral/ogive analysis
Relatively small fields low measurement height: strong high-frequency damping footprint problems (cf. talk by A. Neftel) Frequent calm nights weak/intermittent turbulence, non-stationary conditions enhanced dew formation (on open-path sensor)
? Are parameterised spectral models for the correction of high-frequency damping accurate enough? ? Are integral turbulence characteristics (e.g. /u*) specific enough for w optimum quality control?
Intro Ogive0
Wh tsa “ a i n ogive” ?
statistics: cumulative frequency distribution curve
Some considerations about the
Application of ogive analysis for quality control and spectral correction of eddy covariance fluxes
Christof Ammann, Albrecht Neftel
Content
Content
Motivation for spectral/ogive analysis: methodological flux measurement problems at the Swiss CarboEurope grassland site Some basics about ogives Application examples: High-frequency damping/correction Analysis for intermittency/stationarity of turbulence Conclusions
Site region
Measurement Site near Oensingen
0
N
annual distribution of wind directions
Site plots/fetch
Experimental Plots
200
0
N
150 100
EC systems
local SN scale [m]
Hi
50
g
y wa h
0
-50
- aerodyn. measurement height: z = 0.7 –1.2 m - sensor separation (lateral): s = 16 cm
-100
-150
-200 -300
-250
-200
-150
-100
-50
0
50
100
local WE scale [m]
Site wind
Nocturnal Wind Conditions
50.0 10
CO2 flux windspeed
8
CO2 flux [umol/m2/s]
windspeed ca. 1m above ground (Jun-Oct 2002)
6 0.0 4
frequency of occurrence [rel. units]
daytime nighttime
2
-50.0 20.07.2002 00:00
20.07.2002 12:00
21.07.2002 00:00
21.07.2002 12:00
22.07.2002 00:00
22.07.2002 12:00
0 23.07.2002 00:00
0
1
2
3
4
5
6
7
wind speed [m/s]
windspeed [m/s]
Site motivation
Motivation for spectral/ogive analysis
Relatively small fields low measurement height: strong high-frequency damping footprint problems (cf. talk by A. Neftel) Frequent calm nights weak/intermittent turbulence, non-stationary conditions enhanced dew formation (on open-path sensor)
? Are parameterised spectral models for the correction of high-frequency damping accurate enough? ? Are integral turbulence characteristics (e.g. /u*) specific enough for w optimum quality control?
Intro Ogive0
Wh tsa “ a i n ogive” ?
statistics: cumulative frequency distribution curve