Frequency-comb-based remote sensing of greenhouse gases over kilometer air paths

Rieker, Greg B.; Giorgetta, Fabrizio R.; Swann, William C.; Kofler, J.; Zolot, Alexander M.; Sinclair, Laura C.; Baumann, Esther; Cromer, Christopher L.; Pétron, Gabrielle; Sweeney, Colm; Tans, Pieter P.; Coddington, Ian; Newbury, Nathan R.

doi:10.1364/optica.1.000290

Cited by 327 publications

(205 citation statements)

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“…The improved precision of the DCS A results from higher signal-to-noise ratio of the measured spectra. The DCS B precision is slightly better than previously published precisions from Rieker et al (2014). The grey line illustrates the slope expected for white noise.…”

Section: Comparison Of Open-path Dcs To a Crdsmentioning

confidence: 59%

“…These correspond to relative offsets of −0.85 % for CO 2 , 0.94 % for CH 4 , and 6.9 % for H 2 O, well within the stated uncertainties of HITRAN 2008. In previous DCS measurements, we found slightly different offsets, specifically 1.78 % for CO 2 , 0.20 % for CH 4 , and 1.74 % for H 2 O in Rieker et al (2014) and ∼ 1 % for CO 2 in Giorgetta et al (2015). However, these previous data covered much shorter time spans, used an older CRDS point sensor calibration, and may have included small systematic offsets in the DCS systems due to technical issues discussed in Sect.…”

Section: Comparison Of Open-path Dcs To a Crdsmentioning

confidence: 66%

“…A compact, mobile DCS system such as this one has no moving parts, dense point spacing (200 MHz or 0.0067 cm −1 in this work), effectively no instrument line shape, and a calibration-free wavelength axis as described in Rieker et al (2014) and Truong et al (2016). As a result, it oversamples the 5 GHz wide (0.15 cm −1 ) pressure-broadened gas lines of carbon dioxide, methane, water, and other small molecules without distortion, which should suppress any instrument-specific systematics and allow comparison of DCS data between instruments and over time.…”

Section: Dual-comb Spectroscopymentioning

confidence: 99%

“…Here, each RF tooth represents an optical sample with a separation of 0.0067 cm −1 (or f r = 200 MHz). For longer acquisition times, we implement coherent co-adding of interferograms that maintains this precise optical sampling of the absorbance spectrum (Coddington et al, 2008(Coddington et al, ). al.…”

Section: Dual-comb Spectroscopymentioning

confidence: 99%

“…Recently, open-path dual-comb specPublished by Copernicus Publications on behalf of the European Geosciences Union. 3296 E. M. Waxman et al: Intercomparison of open-path trace gas measurements troscopy (DCS) has emerged as a new technique that could potentially provide precise, accurate, continuous regional measurements of the mole fractions of CO 2 , CH 4 , H 2 O, and HDO over kilometer-scale open paths (Rieker et al, 2014), thereby providing a new open-path sensing capability that falls between point sensing and total-column measurements.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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Abstract. We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km openair 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 2 O), 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 2 O 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. Shortterm 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 .

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Section: Comparison Of Open-path Dcs To a Crdsmentioning

confidence: 59%

Section: Comparison Of Open-path Dcs To a Crdsmentioning

confidence: 66%

Section: Dual-comb Spectroscopymentioning

confidence: 99%

Section: Dual-comb Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2017

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InfraredLIDARApplications in Atmospheric Monitoring

Orr

2017

Encyclopedia of Analytical Chemistry

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The acronym LIDAR stands for LIght Detection And Ranging, an optical analog of RADAR (RAdio Detection And Ranging). The conventional version of LIDAR requires a laser transmitter to launch short pulses of coherent light, which are scattered from atmospheric targets of interest back to an optical receiver, with a time delay that is determined by the range of the target. Optical phenomena in the Earth's atmosphere (e.g. Rayleigh scattering, Raman scattering, Mie scattering, refraction, and resonant absorption) contribute to the amplitude of optical signals returning to the receiver and their characteristic wavelength dependence allows us to measure the concentration and velocity distributions of different atmospheric molecules and aerosol particles. LIDAR backscattering in the infrared (IR) region, on which this article concentrates, is well suited to detecting aerosols (as in clouds or industrial particulate emissions). IR DIAL (DIfferential Absorption Lidar), a variant in which two or more wavelengths are used simultaneously to separate resonant molecular signals from background, enables many molecular species to be monitored by means of their IR absorption spectra. Closely related approaches comprise long‐path IR laser absorption and IPDA (Integrated Path Differential Absorption), with retroreflection from a topographic target (e.g. a strategically located mirror or a hard target, such as the ground in air‐borne applications); these approaches sacrifice optical range information but gain sensitivity because they integrate over all molecules in the optical column between the transmitter/receiver and the reflector or hard target. All of these techniques are vitally dependent on pulsed IR laser technology.

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