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Title: Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

Abstract

We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km open-air paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm −1 (1568 to 1660 nm), corresponding to a 355 cm −1 bandwidth, at 0.0067 cm −1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10 −4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO 2), methane (CH 4), water (H 2O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO 2, 0.35 % (7 ppb) for CH 4, and 0.40 % (36 ppm) for H 2O at  ∼  30 s integration time over the 2-week measurement campaign, which included 24 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO)-calibrated cavity ring-down pointmore » sensor located along the path with good agreement. Short-term and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO 2 and CH 4 that are consistent with the presence of local sources of CO 2 and absence of local sources of CH 4.« less

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Sponsoring Org.:
USDOE Advanced Research Projects Agency - Energy (ARPA-E)
OSTI Identifier:
1389102
Grant/Contract Number:
AR0000539
Resource Type:
Journal Article: Published Article
Journal Name:
Atmospheric Measurement Techniques (Online)
Additional Journal Information:
Journal Name: Atmospheric Measurement Techniques (Online); Journal Volume: 10; Journal Issue: 9; Related Information: CHORUS Timestamp: 2017-09-11 05:51:56; Journal ID: ISSN 1867-8548
Publisher:
Copernicus GmbH
Country of Publication:
Germany
Language:
English

Citation Formats

Waxman, Eleanor M., Cossel, Kevin C., Truong, Gar-Wing, Giorgetta, Fabrizio R., Swann, William C., Coburn, Sean, Wright, Robert J., Rieker, Gregory B., Coddington, Ian, and Newbury, Nathan R. Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers. Germany: N. p., 2017. Web. doi:10.5194/amt-10-3295-2017.
Waxman, Eleanor M., Cossel, Kevin C., Truong, Gar-Wing, Giorgetta, Fabrizio R., Swann, William C., Coburn, Sean, Wright, Robert J., Rieker, Gregory B., Coddington, Ian, & Newbury, Nathan R. Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers. Germany. doi:10.5194/amt-10-3295-2017.
Waxman, Eleanor M., Cossel, Kevin C., Truong, Gar-Wing, Giorgetta, Fabrizio R., Swann, William C., Coburn, Sean, Wright, Robert J., Rieker, Gregory B., Coddington, Ian, and Newbury, Nathan R. Mon . "Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers". Germany. doi:10.5194/amt-10-3295-2017.
@article{osti_1389102,
title = {Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers},
author = {Waxman, Eleanor M. and Cossel, Kevin C. and Truong, Gar-Wing and Giorgetta, Fabrizio R. and Swann, William C. and Coburn, Sean and Wright, Robert J. and Rieker, Gregory B. and Coddington, Ian and Newbury, Nathan R.},
abstractNote = {We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km open-air paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm−1 (1568 to 1660 nm), corresponding to a 355 cm−1 bandwidth, at 0.0067 cm−1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10−4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO2), methane (CH4), water (H2O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO2, 0.35 % (7 ppb) for CH4, and 0.40 % (36 ppm) for H2O at  ∼  30 s integration time over the 2-week measurement campaign, which included 24 °C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO)-calibrated cavity ring-down point sensor located along the path with good agreement. Short-term and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO2 and CH4 that are consistent with the presence of local sources of CO2 and absence of local sources of CH4.},
doi = {10.5194/amt-10-3295-2017},
journal = {Atmospheric Measurement Techniques (Online)},
number = 9,
volume = 10,
place = {Germany},
year = {Mon Sep 11 00:00:00 EDT 2017},
month = {Mon Sep 11 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.5194/amt-10-3295-2017

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