1. Instruments and Platforms for Measuring Atmospheric CO 2 Concentration Britton Stephens NCAR Atmospheric Technology Division

2. Outline Measurement technologies Instruments Precision, potential bias, costs, CDAS implementation Platforms Costs, CDAS implementation Accuracy, or more formally reproducibility, is determined by calibration procedures Measurement expenses are largely a function of the cost of the people who carry them out.

3. Expected from fossil fuel emissions Observations TransCom1 FF Gradients What do existing flask measurements tell us?

4. Dry Mole Fraction of CO 2 BrazilBoulder 370 molecules of CO 2 779630 molecules of N 2 210000 molecules of O 2 10000 molecules of Ar 40000 molecules of H 2 O 5000 molecules of H 2 O Mole Fraction = 355.8 ppm Mole Fraction = 368.2 ppm Dry Mole Fraction = 370.0 ppm For ± 0.1 ppm consistency, need to stabilize to ± 300 ppm H 2 O (or dry to dewpoint of -25 ºC)

5. Absolute Measurement Techniques: Manometric and Gravimetric NOAA/CMDL Manometer: Reproducibility of 0.06 ppm (C. Zhao et al., 1997)

6. Relative Measurement Techniques: Non-dispersive Infrared (NDIR) Spectroscopy (from www.tsi.com) Broadband IR radiation filtered for 4.26 um Cooled emitter and detector Pulsed emitter or chopper wheel 1 or 2 detection cells Advantages: Robust, precise Disadvantages: Non-linear; sensitivity to pressure, temperature, and optical conditions; pressure broadening; power consumption

7. NDIR measurements require calibration gases tied to a common scale NOAA/CMDL scheme for propagation of WMO CO 2 scale: At least 4 points needed for 0.1 ppm consistency Recalibration needed ~ every 3 years due to drift $2000

8. LiCor, Inc. CO 2 Analyzer CMDL Flask Analysis System

9. Typical LiCor Output Signals (from www.cmdl.noaa.gov/ccgg)

10. Intra- and Inter-laboratory agreement still not better than 0.2 ppm

11. CDAS v 1.0 Implementation Sensor Cost Short-term Precision Zero Drift rate Accuracy $7-10,0000.2 ppm in one second <1 ppm per hour Depends on calibration scheme Setup CostOperational CostPrecisionBias $50-$150,000 depending on surface platform (+$10,000 per level on tall towers) $50-100,000 per year depending on surface platform, $1000 per flight on light aircraft 0.05 ppm (± 1σ) 0.2 ppm (± 1σ) LiCor Analyzer Specifications

12. Manual Flask Sampling CDAS v 1.0 Implementation Setup CostOperational CostPrecisionBiasSampling $5000$200 per flask pair (returned as one sample value) + $20*annual flask total 0.05 ppm (± 1σ) 0.2 ppm (± 1σ) Weekly interval 1 1 Selective sampling based on radon in v 2.0

13. Automated Flask Sampling CDAS v 1.0 Implementation Setup CostOperational CostPrecisionBiasSampling $50,000 ($75,000 on buoy) $50 per flask sample ($150 on buoy) + $20*annual flask total 0.1 ppm (± 1σ) 0.2 ppm (± 1σ) Specified 2-24 day interval 1 (from www.cmdl.noaa.gov/ccgg)

14. Atmospheric Observing Systems Boulder, Colorado NOAA SBIR Robust, Precise, CO 2 Analyzer for Unattended Field Use Under Development 1 part in 3000 in 1 minute or less 30 cc/min or less gas usage Unattended field deployment for 6 months or more $5,000 or less when manufactured in quantity

15. CDAS v 1.0 Implementation Sensor Cost Short-term Precision Zero Drift rate Accuracy $5,0000.1 ppm in one minute minimalDepends on calibration scheme Setup CostOperational CostPrecisionBias $500,000 one-time development + $15,000 ($20,000 on light aircraft) (+$5,000 per level on tall towers) $15,000 per year, $500 per flight on light aircraft 0.1 ppm (± 1σ) 0.2 ppm (± 1σ) NOAA/AOS Analyzer Specifications

16. Niwot Ridge Pilot Study August 2002 Jeilun Sun, Steve Oncley, Alex Guenther, Dave Schimel, Don Lenschow, Britt Stephens, Russ Monson, and others.

17. Prototype Inexpensive/Autonomous CO 2 System Research items: Stability of CO 2 in aluminum LPG cylinders Correction for zero drift between calibrations Goals: 1-2 year service schedule Total installation ~ $2000 0.5 ppm accuracy RMT, Ltd., Russia

18. CDAS v 1.0 Implementation Sensor Cost Short-term Precision Zero Drift rate Accuracy $2,0000.5 ppm in one second < 25 ppm per hour Depends on calibration scheme Setup CostOperational CostPrecisionBias $200,000 one-time development + $5,000 (+$2,000 per level on tall towers) $5,000 per year0.2 ppm (± 1σ) 0.5 ppm (± 1σ) NCAR/RMT Analyzer Specifications

19. Sensors in Development

20. Remote Sensing Instruments (not implemented in CDAS v 1.0) Upward-looking Fourier-transform infrared (FTIR) spectrometers (~$300K+) Active and passive satellite CO 2 measurements ($200- $300M) Both ~ 1-3 ppm in column average with potential biases due to land cover type, aerosols, clouds, viewing and sun angle Virtual tall towers (~$50K), 0.2-1.0 ppm for weekly-monthly mid-boundary layer values

22. Ground Station CDAS Implementation Setup CostLocation v 1.0$5000Off of coast allowed to simulate clean air sampling v 2.0 or v 3.0 Scaled based upon location Only allowed on land, co-located with existing meteorological station Point Barrow Alaska

24. Very Tall Tower CDAS Implementation Setup CostLocation v 1.0$100 per meter Anywhere v 2.0 or v 3.0 Co-located with existing tower or budgeted at $1000 per meter WLEF, Wisconsin, USA

25. Towers over 650 feet AGL in U.S. and proximity

26. Light Aircraft Profile CDAS Implementation Setup CostLocation v 1.0$750 per flight Anywhere v 2.0 or v 3.0 Only allowed over or near land, clear air selection allowed Carr, Colorado, USA (from www.cmdl.noaa.gov/ccgg)

27. Volunteer Observing Ship CDAS Implementation Setup CostLocation v 1.0$20,000Great circle route between any two points v 2.0 or v 3.0 Only allowed co-located with existing shipping lanes Freighter Travel, Ltd. Blue Star Line

28. Buoy CDAS Implementation Setup CostLocation v 1.0$25,000Anywhere v 2.0Co-located with existing buoy or budgeted at $100,000 ATLAS Buoy, TAO Array (from NOAA/PMEL)

29. Research Aircraft ($1,500-$20,000 per hour) Research Ships (~$20,000 per day) Additional Platforms (not implemented in CDAS v 1.0)

30. Conclusions There are wide ranges of available instruments and platforms for CO 2 concentration measurements All have different setup and operation costs, precisions, and potential biases Complexity requires a tool for quantitatively assessing creatively designed networks