FLUX MEASUREMENTSOF NON-CO2 GHGS
(INSTRUMENTINTERCOMPARISONS)
3RD TRAINING COURSE/WORKSHOP ONEDDYUH: A SOFTWARE FOR EDDY COVARIANCE FLUX
CALCULATIONHELSINKI 23 – 27.02.2015
O. PELTOLAUNIVERSITY OF HELSINKI, DEP. OF PHYSICS, DIVISION OF ATMOSPHERIC SCIENCES
CONTENT• BACKGROUND• INSTRUMENTATION
• Measurement principle• Available instruments• Intercomparison campaigns
• CH4• N2O
• 1960’s & 1970’s:• eddy covariance was used only for
measuring sensible heat and momentumfluxes during short campaigns
• 1980’s:• fast CO2 analysers (based on NDIR)
started to be developed• 1990’s:
• continuous EC CO2 flux measurementswere set up => FLUXNET
• 1990’s & 2000’s:• First CH4 & N2O EC studies
• 2000’s & 2010’s:• Continuous CH4 & N2O flux
measurements
BACKGROUND
http://celebrating200years.noaa.gov/foundations/weather_obs/wea01106_650.html
BACKGROUND
1970
1990
2000
2010
50
100150
200
250
1990
2000
2010
10
20
30
40
50
2000
2010
10
20
Amount of CH4+eddy covariancepapers
Amount of CO2+eddy covariancepapers
Amount of N2O+eddy covariancepapers
• Gases absorb radiation at certain distinctfrequencies called absorption lines
• This is due to the fact that certain amount ofenergy is needed to switch into certainexited state
• Absorption depends on the gasconcentration (Beer-Lambert law):
• Measure absorption, get the concentration!0
10 lcIAI
e-= =
BASICSABOUTTHEMEASUREMENTPRINCIPLE
• Atmospheric concentrations of CH4 andN2O are approximately 200 and 1000smaller than CO2Þ much more difficult to measure than CO2Þ NDIR method not applicable for CH4 and
N2O, something more accurate is needed
• Laser absorption spectrometers (LAS)measure the shape of the absorption featureaccurately• usually diode lasers working at near-IR
area are used
BASICSABOUTTHEMEASUREMENTPRINCIPLE
• Cavity ring-down spectroscopy (Picarro):• Cavity is used to enhance the signal• Concentration is determined from the
decay of signal vs time
BASICSABOUTTHEMEASUREMENTPRINCIPLE
Picarro Inc.
• Off-axis integrated cavity outputspectroscopy (Los Gatos):• Cavity is used• Integrated absorption is used
BASICSABOUTTHEMEASUREMENTPRINCIPLE
Los Gatos Research
• Tunable laser absorption spectroscopyusing quantum cascade lasers (QCL)(Aerodyne Research):• QCLs work at mid-IR area where absorption
lines are strong => better signal
BASICSABOUTTHEMEASUREMENTPRINCIPLE
Aerodyne Research
• Tunable laser absorption spectroscopyenhanced with wavelength modulationspectroscopy (Licor)• WMS is used to enhance the signal
BASICSABOUTTHEMEASUREMENTPRINCIPLE
Licor Inc.
CH4:• Los Gatos
• FMA (CH4, possibly also H2O)• FGGA (CH4, H2O, CO2)
• Picarro• G1301-f (two out of CO2, CH4, H2O)• G2311-f (CO2, CH4, H2O)
• Licor• LI-7700 (CH4, open-path)
• Aerodyne• Continuous wave QCL• Pulsed QCL
• …
AVAILABLE INSTRUMENTSN2O:
• Los Gatos• N2O, CO, H2O analyser• N2O, CH4, H2O analyser
• Aerodyne• Continuous wave QCL• Pulsed QCL
• …
INTERCOMPARISONCAMPAIGNS
- CH4:- Siikaneva- Cabauw- Other campaigns
- N2O:- Maaninka- Easter Bush
SIIKANEVA CH4INTERCOMPARISON• Campaign:
• Siikaneva oligotrophic open fen• 1.4.-25.10.2010
• Instruments:• Sonic anemometer: Metek USA-1• Methane gas analysers:
• RMT-200 (Los Gatos Research Inc.)• G1301-f (Picarro Inc.)• TGA100A (Campbell Scientific Inc.)
• Needs liquid nitrogen• Dryer
• Prototype-7700 (Li-Cor Inc.)• Open-path instrument• Low power instrument
• Results published in Biogeosciences:Peltola et al. (2013)
• Prototype-7700 housing was filledwith water after ~ 1 month• Lenses of the open cell needed
a lot of cleaning• Picarro G1301-f internal filter was
clogged mid-July• Los Gatos RMT-200 (i.e. FMA) was
working fine throughout the summer
• Cumulative emissions (NB! gapfilled):• FMA: 12.3 g(CH4) m-2
• G1301-f: 11.9 g(CH4) m-2
• TGA-100A: 11.8 g(CH4) m-2
SIIKANEVA CH4INTERCOMPARISON
• For Prototype-7700 the correctionswere on the same order of magnitudeas the measured CH4 flux• Open-path => large WPL
• For closed-path instruments thecorrections were moderate
SIIKANEVA CH4INTERCOMPARISON
• Agreement between RMT-200 and G1301-f is really good• TGA-100A and Prototype-7700 plots show a bit more scatter
• TGA-100A is an old instrument• Prototype-7700 is based on different design
SIIKANEVA CH4INTERCOMPARISON
THE CH4 INTERCOMPARISON CAMPAIGNWAS ORGANIZED WITHIN INGOS FP7INFRASTRUCTURE PROJECT
WHERE: CABAUW, THE NETHERLANDS
WHEN: 6.6.-27.6.2012
RESULTS ARE PUBLISHED INBIOGEOSCIENCES:PELTOLA ET AL. (2014)
CABAUW CH4INTERCOMPARISON
CH4CH4
WINDWIND
MEASUREMENT SETUP
VANOUR MAST
CABAUW BIG TOWER
26 m
87 m
WINDWIND
MEASUREMENT SETUP
VANOUR MAST
CABAUW BIG TOWER
26 m
87 m
6 m
INSTRUMENTS
• G2311-f (Picarro)• CH4,CO2,H2O• Sampling line:
• 30 m long• Heating
• FGGA (LGR)• CH4, CO2, H2O• Sampling line:
• 30 m long• No heating
• LI-7700 (LI-COR)• CH4• Open-path
• DLT-100 (LGR)• CH4• Benchtop FMA• Sampling line:
• 30 m long• No heating
• LI-7500 (LI-COR)• CO2, H2O• Open-path
METEK1
All sampling tubes were made of teflon
INSTRUMENTS
• FMA1 (LGR)• CH4• Sampling line:
• 41 m long• No Heating
• FMA2 (LGR)• CH4, H2O• Sampling line:
• 42 m long• No heating
• G1301-f (Picarro)• CH4, CO2• Sampling line:
• 42 m long• No heating
• Pulsed QCL (Aerodyne)• CH4, N2O• Sampling line:
• 41 m long• No heating• Drier
• LI-7000 (LI-COR)• CO2, H2O• Sampling line:
• 41 m long• No heating
METEK2
All sampling tubes were made of teflon
INSTRUMENTS
• FMA1 (LGR)• CH4• Sampling line:
• 41 m long• No Heating
• FMA2 (LGR)• CH4, H2O• Sampling line:
• 42 m long• No heating
• G1301-f (Picarro)• CH4, CO2• Sampling line:
• 42 m long• No heating
• Pulsed QCL (Aerodyne)• CH4, N2O• Sampling line:
• 41 m long• No heating• Drier
• LI-7000 (LI-COR)• CO2, H2O• Sampling line:
• 41 m long• No heating
METEK2
All sampling tubes were made of teflon
In total 8 CH4 analysers:2011 G2311-f (Picarro)2010 LI-7700 (LI-COR)2009 G1301-f (Picarro)2008 FGGA (LGR)2008 FMA1 (LGR)2006 FMA2 (LGR)2005 DLT-100 (LGR)2005 pulsed QCL (Aerodyne)
CABAUW CH4INTERCOMPARISON
G1301-f, DLT-100 and LI-7700 produced less datathan others
• G1301-f and DLT-100due to data loggingproblems
• LI-7700 duemeasurement cellcontamination
CABAUW CH4INTERCOMPARISONExample of raw data from 22/06/2012,between 10:40-11:00
Picarro instruments have lowest noise levels
LI-7700 is greatly affected by data loggingproblem
G2311-f
G1301-f FGGA
FMA FMA
DLT-100 QCL
CABAUW CH4INTERCOMPARISON
Cumulative CH4fluxes over theperiod range from330 mg(CH4) m-2 to400 mg(CH4) m-2
Instruments with in-situ H2O agree thebest (G2311-f, FGGAand FMA2)
±10%±5%
OTHER CH4INTERCOMPARISONSIwata et al. (2014)
- rice paddy field, LI-7700 & FMA- good agreement- spectral corrections should bedone with care, also for LI-7700
LI-7700
FMA
y=0.99x, r2 = 0.93
Detto et al. (2011)- three sites- LI-7700 and FMA- WPL and spectroscopiccorrections are large for LI-7700 => inevitably affectsthe precision of the fluxestimates
SUMMARY OF CH4INTERCOMPARISONS- Generally CH4 EC analysers agree well, within 10 %- Picarro analysers show lowest noise levels
=> best analysers for locations with low CH4 fluxes- LGR analysers are rugged but need large power hungry pumps- LI-7700 is a low power instrument
=> good for remote locations- LI-7700 needs large WPL and spectroscopic corrections- Best agreement was found between closed-path analysers which measure H2O
simultaneously with CH4
MAANINKA N2OINTERCOMPARISON
Photo: Sami Haapanala
• Campaign:• Bioenergy crop plantation, Maaninka• 20.4.-21.10.2011
• Instruments:• Sonic anemometer: METEK USA-1
• TGA100A (Campbell Scientific)• Needs liquid nitrogen• dryer• CS-TDL
• CW-TILDAS-CS (Aerodyne Research)• AR-CW-QCL
• N2O/CO-23d (Los Gatos Research)• LGR-CW-QCL
• Sonic anemometer: Gill R3-50• QC-TILDAS-76-CS (Aerodyne Research)
• AR-P-QCL
2.2 m
Results are published in Biogeosciences:Rannik et al. (2015)
MAANINKA N2OINTERCOMPARISON
Fertilization
- Daily mean N2O fluxes were around0.1-0.2 nmol m-2 s-1
- After fertilization the fluxes were 2-8nmol m-2 s-1
- CS-TDL was measuring until end ofAugust, LGR-CW-QCL was measuringafter the beginning of Aug
MAANINKA N2OINTERCOMPARISON- White noise in the instrument signal was
estimated from the data with the methodby Lenschow et al. (2000) (lecturetomorrow!)
- CS-TDL: 1.98 ppb- AR-CW-QCL: 0.12 ppb- LGR-CW-QCL: 0.60 ppb- AR-P-QCL: 0.46 ppb
- These numbers essentially tell howprecisely the instruments can measureN2O with 10 Hz sampling frequency
MAANINKA N2OINTERCOMPARISON- The newest analysers AR-CW-QCL and
LGR-CW-QCL agree well- AR-P-QCL underestimated the fluxes
significantly during the high flux period
D. Famulari, E. Nemitz, A. Ibrom, A. Vermeulen, A. Hensen, P. Van Den Bulk, P.Laville, B. Loubet, O. Masher, M. Laborde, A. Lohila, T. Laurila,
I. Mammarella, S. Haapanala , N. Cowan, M. Anderson, C. Helfter
Nitrous oxide fluxes from a Scottish grasslandmeasured by eddy covariance: a comparison between
different systems
Zurich, 4 February 2015 [email protected]
EASTER BUSH N2OINTERCOMPARISON
- Campaign:- Intensively managed grassland,
Edinburgh, UK- 3.6.2013-30.6.2013- Organised within InGOS FP7
infrastructure project- Instruments:
- 2 x Gill HS-50- CEH cw-QCL (AR-CW-QCL)- INRA cw-QCL (AR-CW-QCL)- DTU LGR (LGR-CW-QCL)- FMI LGR (LGR-CW-QCL)
- dryer!- UHEL LGR (LGR-CW-QCL)- ECN QCL (AR-P-QCL)
Results from Famulari et al. (in prep)
10
5
0
-5
N2O
fluxe
snm
olm
-2s-1
172170168166164Day of the year
Fertilisation LGR FMI QCL CEH LGR UHEL p-QCL ECN LGR DTU QCL INRA
EASTER BUSH N2OINTERCOMPARISON
- N2O fluxes were around 0.5-5 nmol m-2 s-1
- AR-P-QCL shows erratic behavior, otherwise instruments agree
Results from Famulari et al. (in prep)
EASTER BUSH N2OINTERCOMPARISON
- Noise values are similar to Maaninkaintercomparison Results from Famulari et al. (in prep)
10-5
10-4
10-3
10-2
Alla
nV
aria
nce
(s2 )
0.1 1 10 100Integration Time (s)
372.0
371.5
371.0
370.5N2O
[ppb
]
18:0024/06/2013
18:10 18:20 18:30
s [ppt]0.1 s 207.08189.0 s 13.25900 s 101.96
Instrument 0.1s
best 15min
RMSE
ECN QCL 767 213 636 137CEH cw-QCL
200 19 38 20
INRA cw-QCL
207 13 102 23
DTU LGR 540 32 256 56FMI LGR 1046 27 194 91UHEL LGR 621 40 172 81
8
6
4
2
0
-2
LGR
FMI
86420-2AVERAGE FLUX
1:1offset = 2.5e-5slope = 0.98r2 = 0.97
Results from Famulari et al. (in prep)
8
6
4
2
0
-2Q
CL
CE
H86420-2
AVERAGE FLUX
1:1
offset = -8.9e-6slope = 1.03r2 = 0.99
8
6
4
2
0
-2
QC
LIN
RA
86420-2AVERAGE FLUX
1:1offset = 3.3e-5slope = 1.05r2 = 0.95
8
6
4
2
0
-2
p-Q
CL
ECN
86420-2AVERAGE FLUX
1:1offset = -4.5e-4slope = 1.06
8
6
4
2
0
-2
LGR
DTU
86420-2AVERAGE FLUX
1:1offset = -7e-5slope = 1.06r2 = 0.89
8
6
4
2
0
-2
LGR
UH
EL
86420-2AVERAGE FLUX
1:1offset = -3.1e-5slope = 0.98r2 = 0.94
Results fromFamulari et al.(in prep)
EASTER BUSH N2OINTERCOMPARISON
SUMMARY OF N2OINTERCOMPARISONS
- Generally N2O analysers agree within 10 % (not in Maaninka)- Using dryer vs not using did not seem make much difference
- The new Aerodyne laser was most precise- Best for low flux conditions
- Traditionally N2O fluxes have been measured only at agriculturalareas where fluxes are high
- With the latest generation lasers, it is possible to measure verysmall fluxes, potential for non-agricultural fluxes and uptakestudies
- Huge development has been made during the last decade in non-CO2 GHGinstrumentation
- The new analysers are more rugged and better suited for field conditions- Flux measurements can be conducted in places which were previously unavailable
(power restrictions, too low fluxes)- Bright future for non-CO2 GHG flux measurements!
SUMMARY
THANKS!
Photo taken by SamiHaapanala
