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 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 XCO 2 Data” – C.E. Miller

Total Carbon Column Observing Network Sites Current Near-IR Solar Observatory Planned Near-IR Solar Observatory Other 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 CO 2 monitoring at six levels on Tall Tower CO 2 flux measurements Weekly flask sampling and monthly aircraft profiles by NOAA CMDL 447-m WLEF tower

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: CO 2, CH 4, CO, N 2 O, H 2 O, HDO, HF, and O 2. Bruker 120HR spectrometer

Spectral Fitting of Carbon Dioxide Single forward spectrum (resolution = 0.02 cm -1 ) recorded at 9:30 am on 9 September Column CO 2 = x molecules cm -2 Column CO 2 / Total Dry Column = ± 0.37 ppmv

Calibration of Absolute Column CO 2 Using Aircraft Data Intercontinental Chemical Transport Experiment – North America (INTEX-NA) NASA DC-8 and King Air measured in situ CO 2 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 CO 2 retrievals on the same scale as the in situ network. DC-8 Flight Path and Photograph from 12 July:

FTS Column and Aircraft In Situ Data – 12 July 04 Aircraft Column / Total Dry Column = ± 0.52 ppmv FTS Column / Total Dry Column = ± 0.25 ppmv ± 0.27 ppmv AIRCRAFT PROFILE:FTS RETRIEVAL:

Comparison of FTS Column and Integrated Aircraft CO 2

Diurnal Variation of Column and Tall Tower CO 2 Arlyn Andrews – preliminary NOAA CMDL Tall Tower data Relationship between column and in situ CO 2 is influenced by: Drawdown due to photosynthesis Regional mixing Boundary layer dynamics 12 ppmv 15 ppmv

Column and Tall Tower CO 2 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 CO 2 Measurements” – K.D. Corbin

Initial TCCON Results LocationLat.Lon.InstitutionOperational Park Falls, WisconsinUnited States45.9 N90.3 WCaltechMay 2004 LauderNew Zealand45.0 S169.7 ENIWAJune 2004 DarwinAustralia12.4 S90.3 E U Wollongong Caltech Sept 2005

TCCON Measurements and Model Predictions Vanessa Sherlock and Brian Connor – Lauder CO 2 columns Seth Olsen – MATCH model results

Summary Park Falls, Wisconsin: An automated solar observatory has been operational since May Demonstrated precision of ~0.1% for column CO 2. Linear relationship between column CO 2 and integrated aircraft profiles can be used to correct the absolute accuracy of the column CO 2 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 CO 2.

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 CO 2 profiles:Stephanie Vay King Air CO 2 profiles:Steven Wofsy and Daniel Matross Stratospheric CO 2 profile:Bruce Daube and Steven Wofsy Funding:NASA Atmospheric Chemistry, Modeling, and Analysis Program NASA Terrestrial Ecology Program NASA Orbiting Carbon Observatory

Additional Material

Solar Spectrum Recorded in Park Falls, Wisconsin InGaAs Detector Si Diode Detector Wavelength (cm -1 ) Transmission CO 2 O2O2 O2O2 Single forward spectrum recorded at 9:30 am on 9 Sept Resolution = 0.02 cm -1. Signal-to-noise: InGaAs Detector ~885; Si Diode Detector ~465 Individual CO 2 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

Most Recent Park Falls Data ∆Column CO 2 on sunny days: ~3 ppmv day -1 = gC m -2 day -1 Davis et al (2003) average daytime NEE June – August 1997 = 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 CO 2 extends to surface AIRCRAFT PROFILE: ABOVE AIRCRAFT PROFILE: Tropopause taken from NCEP reanalysis Assume that median free tropospheric CO 2 extends to tropopause. Stratospheric CO 2 profile is taken from September 2004 balloon profile. Assume that CO 2 = f(Θ) is reasonably constant in the stratosphere over this time difference.

Averaging Kernels in FTS – Aircraft Comparison Definition of the averaging kernel: X_hat = (I – A) × X a + A × X X_hat = retrieved CO 2 X = true CO 2 A = averaging kernel X a = a priori profile I = identity matrix

Model Predictions for Column CO 2 at 45 °N and 45 °S FTS MeasurementModel Prediction Park Falls11 ppmv8.5 ppmv Lauder2 ppmv Observed peak-to-peak seasonal amplitude of measured column CO 2 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 CO 2 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 – September Wet monsoonal season from December – March Transitional period between Existing ARM measurements: Cloud properties, surface meteorology, atmospheric profiling, aerosol properties

Future Measurement Plans LocationLat.Lon.InstitutionOperational PomonaCalifornia34 N117 WCaltech / JPLDec 2006 LamontOklahoma37 N98 WCaltech / JPLMay 2007

TCCON Measurements and Model Predictions Vanessa Sherlock and Brian Connor – Lauder CO 2 columns Seth Olsen – MATCH model results