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Bringing the SI to Global Atmospheric Greenhouse Gas Measurement


We are developing a comprehensive next-generation greenhouse gas (GHG) calibration system capable of extending SI traceability to global satellite remote sensing and terrestrial remote sensing platforms across all relevant spatial scales. We are aiming to achieve this by directly linking molecular spectroscopy to the SI and by exploiting this link to develop frequency comb remote sensing instruments with unprecedented open path accuracy. This will allow direct calibration of GHG remote sensing satellites and will provide the critical methane and carbon dioxide metrology necessary to monitor the natural background and anthropogenic sources across the globe, limit unintended emissions, enrich public safety, and guide climate policy


Montage of photos showing gas cylinders, an optical bench, experimental instrumentation, and an illustration of satellite remote sensing, with a centered emblem of the 7 fundamental SI units.

Measurement traceability to the SI will permit rigorous assessment of greenhouse gases with unprecedented accuracy. 

Credit: NIST

This multifaceted program leverages expertise in three complementary technical focus areas- all of which involve SI-traceable measurements of relevant atmospheric species such as carbon dioxide, methane, water vapor and oxygen. The efforts include gravimetrically based preparation of primary standard gas mixtures comprising GHGs in air, accurate and precise laboratory measurements of spectroscopic reference data to advance first-principles models of light-matter interaction in the atmosphere, and application of three custom field-based spectrometer technologies (wavelength-multiplexed laser spectrometry with optical frequency combs, differential absorption LIDAR, and laser heterodyne radiometry) to measure concentrations of relevant atmospheric components over extended horizontal and vertical pathlengths.  The gas standards are required for accurate spectroscopic determination of molecular line intensities, which are intrinsic properties constituting species-specific “molecular rulers” for determining amount of substance from observations of light absorption.  Our laboratory measurements of molecular line intensities and other parameters are also used to benchmark ab initio calculations of these same quantities, providing improved confidence in the models of light absorption and greatly extending coverage to include a much more extensive range of wavelengths, temperature, and pressure.  The field campaigns based on the new remote sensing technologies incorporate these latest spectroscopic data and models.  An overarching goal is to establish next-generation remote-sensing validation techniques that yield accurate data products needed for the realization of long-term continuity in GHG observations

Associated Publications

1 Reed, Z. D,, Tran, H,, Ngo H. N,, Hartmann, J. -M., and Hodges J. T,,  “Effect of non-Markovian collisions on measured integrated line-shapes of CO,” Physical Review. Letters. 130, 143001 (2023) 

2. Lisak, D., Charczun, D., Nishiyama, A., Voumard, T., Wildi, T., Kowzan, G., Brasch, V., Herr, T., Fleisher, A. J., Hodges, J. T., Ciurylo, R., Cygan, A., and Maslowski, P., "Dual-comb cavity ring-down spectroscopy," Scientific Reports, 12, (2022). 

3. Long, D. A., Adkins, E. M., Mendonca, J., Roche, S., and Hodges, J. T., "The effects of advanced spectral line shapes on atmospheric carbon dioxide retrievals," Journal of Quantitative Spectroscopy & Radiative Transfer, 291, (2022). 

4. Fleurbaey, H., Reed, Z. D., Adkins E. M., Long, D. A., and Hodges J. T., “High accuracy spectroscopic parameters of the 1.27 mm band of O2 measured with comb-referenced, cavity ring-down spectroscopy,” Journal of Quantitative Spectroscopy. and Radiative Transfer, 270, 107684 (2021). 

5. Bailey, D. M., Zhao, G., and Fleisher, A. J., "Precision Spectroscopy of Nitrous Oxide Isotopocules with a Cross-Dispersed Spectrometer and a Mid-Infrared Frequency Comb," Analytical Chemistry, 92, 13759-13766 (2020). 

6 Brewer, P. J., Kim, J. S., Lee, S., Tarasova, O. A., Viallon, J., Flores, E., Wielgosz, R. I., Shimosaka, T., Assonov, S., Allison, C. E., van der Veen, A. M. H., Hall, B., Crotwell, A. M., Rhoderick, G. C., Hodges, J. T., Mahn, J., Zellweger, C., Moossen, H., Ebert, V., and Griffith, D. W. T., "Advances in reference materials and measurement techniques for greenhouse gas atmospheric observations," Metrologia, 56, (2019). 

7. Plusquellic, D. F., Wagner, G. A., Briggman, K., Fleisher, A. J., Long, D. A., and Hodges, J. T., "Simultaneous DIAL, IPDA and point sensor measurements of the greenhouse gases, CO2 and H2O," 2019 Conference on Lasers and Electro-Optics (Cleo), (2019). 

8. Rhoderick, G. C., Kelley, M. E., Miller, W. R., Norris, J. E., Carney, J., Gameson, L., Cecelsld, C. E., Harris, K. J., Goodman, C. A., Srivastava, A., and Hodges, J. T., "NIST Standards for Measurement, Instrument Calibration, and Quantification of Gaseous Atmospheric Compounds," Analytical Chemistry, 90, 4711-4718 (2018). 

9. Rhoderick, G. C., Kitzis, D. R., Kelley, M. E., Miller, W. R., Hall, B. D., Dlugokencky, E. J., Tans, P. P., Possolo, A., and Carney, J., "Development of a Northern Continental Air Standard Reference Material," Analytical Chemistry, 88, 3376-3385 (2016). 

9. Lin, H., Reed, Z. D., Sironneau, V. T., and Hodges, J. T., "Cavity ring-down spectrometer for high-fidelity molecular absorption measurements," Journal of Quantitative Spectroscopy & Radiative Transfer, 161, 11-20 (2015). 

10. Long, D. A., Wojtewicz, S., Miller, C. E., and Hodges, J. T., "Frequency-agile, rapid scanning cavity ring-down spectroscopy (FARS-CRDS) measurements of the (30012)<-(00001) near-infrared carbon dioxide band," Journal of Quantitative Spectroscopy & Radiative Transfer, 161, 35-40 (2015). 

11. Wagner, G., Maxwell, S., Douglass, K., Long, D. A., Hodges, J. T., Fleisher, A. J., and Plusquellic, D. F., Low Power Integrated Path Differential Absorption Lidar Detection of CO2, CH4 and H2O over a 5.5 km Path using a Waveform Driven EO Sideband Spectrometer 2015. 

12. van Zee, R. D. and Spinler, S., "Real option valuation of public sector R&D investments with a down-and-out barrier option," Technovation, 34, 477-484 (2014). 

13. Long, D. A. and Hodges, J. T., "On spectroscopic models of the O-2 A-band and their impact upon atmospheric retrievals," Journal of Geophysical Research-Atmospheres, 117, (2012). 

14. Rhoderick, G. C., Carney, J., and Guenther, F. R., "NIST Gravimetrically Prepared Atmospheric Level Methane in Dry Air Standards Suite," Analytical Chemistry, 84, 3802-3810 (2012). 

15. Vess, E. M., Wallace, C. J., Campbell, H. M., Awadalla, V. E., Hodges, J. T., Long, D. A., and Havey, D. K., "Measurement of H2O Broadening of O-2 A-Band Transitions and Implications for Atmospheric Remote Sensing," Journal of Physical Chemistry A,  116, 4069-4073 (2012). 

16. Douglass, K. O., Maxwell, S. E., Plusquellic, D. F., Hodges, J. T., van Zee, R. D., Samarov, D. V., and Whetstone, J. R., "Construction of a High Power OPO Laser system for Differential Absorption LIDAR," Lidar Remote Sensing for Environmental Monitoring Xii, 8159, (2011). 


Created August 17, 2022, Updated October 11, 2023