Initial Results from the Total Carbon Column Observing Network R.A. Washenfelder 1, V. Sherlock 2, B.J. Connor 2, G.C. Toon 3, and P.O. Wennberg 1 1 California.

Initial Results from theTotal Carbon Column Observing Network

R.A. Washenfelder1, V. Sherlock2, B.J. Connor2, G.C. Toon3, and P.O. Wennberg1

1 California Institute of Technology (Pasadena, CA)2 National Institute of Water and Atmospheric Research (Lauder, New Zealand)3 NASA Jet Propulsion Laboratory (Pasadena, CA)

Total Carbon Column Observing Network

TCCON is a new network of ground-based near-infrared Fourier Transform Spectrometers dedicated to measurement of greenhouse gases.

Goals for the TCCON Network

1) Assist in constraining the global carbon budget

Compared to surface in situ measurements, column measurements are:• Less sensitive to local sources and sinks• Less sensitive to diurnal and seasonal “rectifier” effects

2) Validate satellite remote sensing instruments

• The Orbiting Carbon Observatory (OCO)• SCIAMACHY• The Greenhouse Gases Observing Satellite (GOSAT)

To learn more about satellite validation:“Overview of OCO Validation” – R. J. Salawitch“Precision Requirements For Space-Based XCO2 Data” – C.E. Miller

Total Carbon Column Observing Network Sites

Current Near-IR Solar ObservatoryPlanned Near-IR Solar ObservatoryOther Future Possibilities

Tall Tower Site in Park Falls, Wisconsin

The laboratory is located next to the 447-m tall WLEF tower, in the Chequamegon National Forest.

This is a site of intensive field measurements by NOAA and other collaborators:• Continuous CO2 monitoring at six levels on Tall Tower• CO2 flux measurements• Weekly flask sampling and monthly aircraft profiles by NOAA CMDL

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Park Falls Automated Solar Observatory

Solar tracker

Scanner

Interferometer

Detectors

Solar Beam

Direct sunlight is absorbed at specific wavelengths by atmospheric gases.A Fourier Transform Spectrometer (FTS) records direct solar spectra at high spectral resolution.

Measurements are acquired when the sun is unobscured:• 105 seconds per spectrum.• Full spectrum obtained between

3,900 – 15,600 cm-1 (2.56 – 0.64 μm).• Instrumental alignment is monitored using a sealed cell containing HCl gas.

Gases with absorption features in the near-IR:

CO2, CH4, CO, N2O, H2O, HDO, HF, and O2.

Bruker 120HR spectrometer

Spectral Fitting of Carbon Dioxide

Single forward spectrum (resolution = 0.02 cm-1) recorded at 9:30 am on 9 September 2004.Column CO2 = 7.6466 x 1021 molecules cm-2

Column CO2 / Total Dry Column = 373.94 ± 0.37 ppmv

Calibration of Absolute Column CO2 Using Aircraft Data

Intercontinental Chemical Transport Experiment – North America (INTEX-NA)• NASA DC-8 and King Air measured in situ CO2 during tower profiles• Eight unique aircraft profiles:

DC-8: July 12, July 15 (twice)King Air: July 14, July 15, August 14, August 15 (twice)

Allows us to place our column CO2 retrievals on the same scale as the in situ network.

DC-8 Flight Path and Photograph from 12 July:

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Color = Altitude from 0 - 12 km

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FTS Column and Aircraft In Situ Data – 12 July 04

Aircraft Column / Total Dry Column =372.5 ± 0.52 ppmv

FTS Column / Total Dry Column = 375.5 ± 0.25 ppmv371.4 ± 0.27 ppmv

AIRCRAFT PROFILE: FTS RETRIEVAL:

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CO2 VMR (ppmv)

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Sept 2004 Balloon Profile(Daube and Wofsy)

In Situ CO2 (Vay)

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Comparison of FTS Column and Integrated Aircraft CO2

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CO2 6220 cm-1

band = 1.0076 x Aircraft Column

CO2 6339-1

band = 0.995 x Aircraft Column One to one line

Comparison of FTS Column and Integrated Aircraft CO2

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Column Tower at 11-m Tower at 76-m Tower at 396-m

Diurnal Variation of Column and Tall Tower CO2

Arlyn Andrews – preliminary NOAA CMDL Tall Tower data

Relationship between column and in situ CO2 is influenced by:• Drawdown due to photosynthesis• Regional mixing• Boundary layer dynamics

12 ppmv

15 ppmv

Column and Tall Tower CO2 during May 2004 – May 2005

Related poster: “Using A High Resolution Coupled Ecosystem-Atmosphere Model To Evalulate Spatial, Temporal, and Clear-Sky Errors in Satellite CO2 Measurements” – K.D. Corbin

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FTS Column Daytime Average Tower at 76-m (11:00 - 15:00 CDT) Tower at 396-m (11:00 - 15:00 CDT)

Initial TCCON Results

Location Lat. Lon. Institution Operational

Park Falls, Wisconsin United States 45.9 N 90.3 W Caltech May 2004

Lauder New Zealand 45.0 S 169.7 E NIWA June 2004

Darwin Australia 12.4 S 90.3 E U Wollongong

CaltechSept 2005

TCCON Measurements and Model Predictions

Vanessa Sherlock and Brian Connor – Lauder CO2 columnsSeth Olsen – MATCH model results

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Park Falls, Wisconsin Lauder, New Zealand Darwin, Australia

LINE = Olsen and Randerson model

Summary

Park Falls, Wisconsin:

• An automated solar observatory has been operational since May 2004.

• Demonstrated precision of ~0.1% for column CO2.

• Linear relationship between column CO2 and integrated aircraft profiles can be used to correct the absolute accuracy of the column CO2 measurements.

Total Carbon Column Observing Network:

• Initial comparisons between Park Falls, Wisconsin and Lauder, New Zealand show that these measurements will capture the interhemispheric seasonal cycle of CO2.

Acknowledgements

Caltech FTS data: Jean-Francois Blavier, Geoffrey Toon, Zhonghua Yang, Yael Yavin, Paul Wennberg

Lauder FTS data: Vanessa Sherlock and Brian Connor

WLEF Tall Tower data: Arlyn Andrews

DC-8 CO2 profiles: Stephanie VayKing Air CO2 profiles: Steven Wofsy and Daniel Matross

Stratospheric CO2 profile: Bruce Daube and Steven Wofsy

Funding: NASA Atmospheric Chemistry, Modeling, and Analysis ProgramNASA Terrestrial Ecology ProgramNASA Orbiting Carbon Observatory

Additional Material

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Solar Spectrum Recorded in Park Falls, Wisconsin

InGaAsDetector

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CO2CO2 O2O2

Single forward spectrum recorded at 9:30 am on 9 Sept 2004. Resolution = 0.02 cm -1.Signal-to-noise: InGaAs Detector ~885; Si Diode Detector ~465

Individual CO2 Lines:

Analysis Method: GFIT

• Line-by-line fitting algorithm for solar absorption spectra

• Developed at the Jet Propulsion Laboratory by Geoff Toon

• Least squares analysis in spectral window to determine slant column abundances for the absorbing gases

• Definition of the fitting residual:

• Atmosphere is represented by 70 vertical levels in forward model

• Pressure and temperature profiles taken from NCEP Reanalysis, with 17 levels from 1000 – 10 mb with 1°×1° geographic resolution

• Climatological temperature profiles used for levels with pressures ≤10 mb

NM

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Park Falls Column Daily average

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Most Recent Park Falls Data

∆Column CO2 on sunny days: ~3 ppmv day-1 = -12.3 gC m-2 day-1

Davis et al (2003) average daytime NEE June – August 1997 = -4.46 gC m-2 day-1

Treatment of Aircraft Profiles

Profile has been integrated from surface pressure to top of atmosphere.

BELOW AIRCRAFT PROFILE:Assume that median PBL CO2 extends to surface

AIRCRAFT PROFILE:

ABOVE AIRCRAFT PROFILE:Tropopause taken from NCEP reanalysis

Assume that median free tropospheric CO2 extends to tropopause.Stratospheric CO2 profile is taken from September 2004 balloon profile.Assume that CO2 = f(Θ) is reasonably constant in the stratosphere over this time difference.

dp

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Averaging Kernels in FTS – Aircraft Comparison

Definition of the averaging kernel:X_hat = (I – A) × Xa + A × X

X_hat = retrieved CO2

X = true CO2

A = averaging kernelXa = a priori profileI = identity matrix

Model Predictions for Column CO2 at 45 °N and 45 °S

FTS Measurement Model Prediction

Park Falls 11 ppmv 8.5 ppmv

Lauder 2 ppmv 2 ppmv

Observed peak-to-peak seasonal amplitude of measured column CO2

compared to model predictions by Olsen and Randerson [2004]:

Model predictions are roughly consistent with actual column measurements.Plans for continued investigation:

Modeling • accuracy of surface flux inventories • parameterization of mixing

Column measurements: • verify that no FTS retrieval bias exists which is dependent on solar zenith angle e.g. averaging kernels or systematic error in the CO2 air-broadened width parameters

Inherent differences between the measurement and the model • comparison of spatially-averaged model results with point observations

Darwin, Australia Site

DOE Atmospheric Radiation Measurement Site

Located on northern Australian coast in the tropics

Three seasons:Dry continental regime from May – SeptemberWet monsoonal season from December – MarchTransitional period between

Existing ARM measurements: Cloud properties, surface meteorology, atmospheric profiling, aerosol properties

Future Measurement Plans

Location Lat. Lon. Institution Operational

Pomona California 34 N 117 W Caltech / JPL Dec 2006

Lamont Oklahoma 37 N 98 W Caltech / JPL May 2007

TCCON Measurements and Model Predictions

Vanessa Sherlock and Brian Connor – Lauder CO2 columnsSeth Olsen – MATCH model results

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Park Falls, Wisconsin Lauder, New Zealand Darwin, Australia

LINE = Olsen and Randerson model