Precision CO2 on Short towers
A first evaluation for Loobos-NL
Bart Kruijt and Jan Elbers
introduction
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For overview of activity 2.7, See talk Tuula Aalto
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Idea of ‘short tower CO2’:
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Low cost, higher density
Concurrent with (CarboEurope) flux and meteo sites
Would allow ‘virtual tall tower approach’ (modified fluxgradient)
Regional inversion, local interpretation of profiles and
temporal dynamics
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This talk: a preliminary analysis for Loobos:
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functioning
Error
Spatial consistency
Plans for use of data
Loobos was last in getting operational:
-low power
-only GPRS connection, no internet
-Code needed substantial rewriting
- Loobos was the FIRST in going on-line!
- we have a beautiful moderate-cost system now!
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AIRCOA on-line
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majadas
Full record top level at Loobos with error bars
2D Graph 4
500
[CO2] top (ppm)
480
460
440
420
400
380
okt-2007
dec-2007
feb-2008
apr-2008
jun-2008
500
Loobos: mean top level CO2
between 12:00 and 14:00 (UTC+1)
pm [CO2] at Loobos (ppm)
480
460
440
420
400
380
okt-07
dec-07
feb-08
apr-08
jun-08
2
absolute error Loobos (signal-reference)
2D Graph 2
0
2.0
-1
-2
okt-07
1.5
dec-07
Col 2 vs Col 52
error (ppm)
Error (ppm)
1
1.0
0.5
feb-08
apr-08
jun-08
0.0
-0.5
-1.0
0
5
10
15
20
25
Box temperature
30
35
40
Day AND night!
25
Loobos error distribution since February 2008
Frequency
20
15
10
5
0
-1.0
-0.5
0.0
0.5
Absolute error (ppm)
1.0
Other sites?
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Finland:
+0.4
majadas
-0.5
Nov -07
Jun -08
URAS - LiCor
NCAR specified 0.1- 0.2 ppm precision.
Why are we doing worse?
-Temperature and humidity ranges larger (less
continental, no cabins)
-Reference gas (dry) shares part of tubing with
sample (wet)
-Pressure gradient from reference to IRGA 
vulnerability to leaks
Loobos
Cabauw
Cabauw CO2 12:00-14:00
all levels
460
200 m
120 m
60 m
20 m
440
420
400
380
okt-07
Cabauw PM vertical gradients
nov-07
dec-07
jan-08
feb-08
mrt-08
apr-08
mei-08
4
PM difference (ppm)
PM [CO2 ] (ppm)
480
2
0
-2
-4
okt-07
120 m - 200 m
60 m - 200 m
20 m - 200 m
nov-07
dec-07
jan-08
feb-08
mrt-08
apr-08
mei-08
Loobos 24 m
Cabauw 60 m
420
410
400
390
380
05-nov-07
19-nov-07
03-dec-07
17-dec-07
31-dec-07
14-jan-08
28-jan-08
Loobos (top) and Cabauw (60 m) PM values
PM CO2 at 24 m (LOO) and 60 m (CBW)
PM CO2 at 24 m (LOO) and 60 m (CBW)
Loobos (top) and Cabauw (60 m) PM values
430
430
Loobos 24 m
Cabauw 60 m
420
410
400
390
380
04-feb-08
18-feb-08
03-mrt-08
17-mrt-08
31-mrt-08
14-apr-08
28-apr-08
Difference
Cabauw - Loobos
2D Graph 11
North
440
Loobos (ppm)
Amateuristic
430
analysis
asking for420
410
modellers!
West
400
390
380
380
Loobos
CBW
CBW
CBW
CBW
Cabauw
390
400
410
420
East
20 m
60 m
120 m
200 m
430
440
Cabauw (ppm)
South
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Compare:
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Majadas - La Muela
Le Bray – Puy de Dome
Tharandt – Heghatsal
Hyyttiala – Pallas
… all together!
Plans for analysis (Loobos, all sites)
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(limited time)
Improve accuracy (??)
Explore extrapolation to CBL (‘VTT’)
Explore use in regional inversion (RAMS-VU) in
Dutch CO2 budgetting study
Explore use in micrometeorology
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 can the rich information on (all) fluxes, profiles and
meteo help in vertical scaling, in regional modelling and
inversion?
Conclusion
-Accuracy so far + / - 0.5 ppm - TBI ?
-Beautiful in-canopy gradients waiting for analysis
-Useful data for use in (regional) inversions?
© Wageningen UR