Assessment of errors and biases in retrievals of X&amp;lt;sub&amp;gt;CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;&amp;lt;/sub&amp;gt;, X&amp;lt;sub&amp;gt;CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;&amp;lt;/sub&amp;gt;,
X&amp;lt;sub&amp;gt;CO&amp;lt;/sub&amp;gt;, and X&amp;lt;sub&amp;gt;N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;/sub&amp;gt; from a 0.5 cm&amp;lt;sup&amp;gt;–1&amp;lt;/sup&amp;gt; resolution solar-viewing
spectrometer

Hedelius, Jacob K.; Viatte, Camille; Wunch, Debra; Roehl, Coleen M.; Toon, G. C.; Chen, Jia; Jones, Taylor; Wofsy, Steven C.; Franklin, Jonathan; Parker, Harrison; Dubey, Manvendra K.; Wennberg, P. O.

doi:10.5194/amt-9-3527-2016

Cited by 55 publications

(57 citation statements)

References 41 publications

(92 reference statements)

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“…Here, we find agreement between two DCS instruments that is an order of magnitude better and is comparable to that achieved with highly-calibrated, state-of-the-art, solar-looking FTIRs that retrieve vertical column measurements (Messerschmidt et al, 2011; Frey et al, 2015; Hedelius et al, 2016); however, open-path DCS does not require instrument-specific calibrations (e.g. of the instrument line shape) and provides a very different capability by retrieving the dry mole fractions across regional, kilometer-scale paths over day and night in a mobile platform.…”

Section: Introductionsupporting

confidence: 70%

Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers

Waxman¹,

Cossel²,

Truong³

et al. 2017

Preprint

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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 two-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6021 to 6388 cm−1 (1565 to 1661 nm), corresponding to a 367 cm−1 bandwidth, at 0.0067 cm−1 sample spacing. The measured absorption spectra agree with each other to within 5×10−4 without any external calibration of either instrument. The absorption spectra are fit to retrieve 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 over the two-week measurement campaign, which included 23 °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 WMO-calibrated cavity ringdown point sensor located along the path with good agreement. Short-term and long-term differences between the two systems are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the two-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.

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Section: Introductionsupporting

confidence: 70%

Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers

Waxman¹,

Cossel²,

Truong³

et al. 2017

Preprint

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“…The ratio of CH 4 over O 2 cancels systematic errors; therefore, the precision for XCH 4 (see equations (1)-(2) below for definition) is higher than for the VCD. The single sounding precision of XCH 4 for 10 coadded scans is~0.33 ppbv based on Hedelius et al (2016; did not coadd scans).…”

Section: Retrievalsmentioning

confidence: 98%

“…CH 4 is retrieved from EM27/SUN solar spectra (5,000-11,000 cm −1 ) using the spectral region at 5,897-6,145 cm −1 and O 2 at 7,765-8,005 cm −1 (Frey et al, 2015); the PROFFIT code is used for the retrievals (Hase et al, 2004). The single sounding precision of XCH 4 for 10 coadded scans is~0.33 ppbv based on Hedelius et al (2016; did not coadd scans). The single sounding precision of XCH 4 for 10 coadded scans is~0.33 ppbv based on Hedelius et al (2016; did not coadd scans).…”

Section: Retrievalsmentioning

confidence: 99%

Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

Kille

Chiu

Frey

et al. 2019

Geophysical Research Letters

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This proof‐of‐concept study demonstrates that methane (CH4) emissions from natural gas (NG) and agriculture can be disentangled using the concept of excess column observations. A network of cost‐effective sensors measured excess column‐averaged dry‐air mole fractions for CH4 (ΔXCH4), ethane (ΔXC2H6 as NG tracer), and ammonia (ΔXNH3 from agriculture) in the Denver‐Julesburg Basin during March 2015. ΔXCH4 varied up to 17 ppb and was >3 times higher with winds from directions where NG is produced. The ΔXCH4 variance is explained by variations in the C2H6‐NH3 tracer pair, attributing 63 ± 17% to NG, 25 ± 10% to agriculture, and 12 ± 12% to other sources. The ratios ΔXC2H6/ΔXCH4 (16 ± 2%; indicates wet NG) and ΔXNH3/ΔXCH4 (43 ± 12%) were compatible with in situ measured ratios. Excess columns are independent of boundary layer height, characterize gases in the open atmosphere, are inherently calibrated, average over extended spatial scales, and provide a complementary perspective to quantify and attribute CH4 emissions on regional scales.

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“…By the TC-CON measurements, the relevant wavenumber region 4000-11000 cm −1 , corresponding to wavelengths λ between 0.9 and 2.5 µm, is covered so that, among other species, O 2 , CO 2 , CH 4 , CO and H 2 O can be retrieved. A figure showing the spectral range of TCCON and the EM27/SUN can be found in Hedelius et al (2016), Fig. 1.…”

Section: Tccon Data Setmentioning

confidence: 99%

“…The previously described Bruker EM27/SUN portable FTIR spectrometer Frey et al, 2015;Hedelius et al, 2016) is a promising instrument to overcome the above-mentioned shortcomings as it is a mobile, reliable, easy-to-deploy and low-cost supplement to the Bruker IFS 125HR spectrometer used in the TCCON network. So far the EM27/SUN was mainly used in campaigns for the quantification of local sinks and sources Chen et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Building the COllaborative Carbon Column Observing Network (COCCON): long-term stability and ensemble performance of the EM27/SUN Fourier transform spectrometer

et al. 2019

Self Cite

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In a 3.5-year long study, the long-term performance of a mobile, solar absorption Bruker EM27/SUN spectrometer, used for greenhouse gas observations, is checked with respect to a co-located reference Bruker IFS 125HR spectrometer, which is part of the Total Carbon Column Observing Network (TCCON). We find that the EM27/SUN is stable on timescales of several years; the drift per year between the EM27/SUN and the official TCCON product is 0.02 ppmv for XCO 2 and 0.9 ppbv for XCH 4 , which is within the 1σ precision of the comparison, 0.6 ppmv for XCO 2 and 4.3 ppbv for XCH 4 . The bias between the two data sets is 3.9 ppmv for XCO 2 and 13.0 ppbv for XCH 4 . In order to avoid sensitivity-dependent artifacts, the EM27/SUN is also compared to a truncated IFS 125HR data set derived from full-resolution TCCON interferograms. The drift is 0.02 ppmv for XCO 2 and 0.2 ppbv for XCH 4 per year, with 1σ precisions of 0.4 ppmv for XCO 2 and 1.4 ppbv for XCH 4 , respectively. The bias between the two data sets is 0.6 ppmv for XCO 2 and 0.5 ppbv for XCH 4 . With the presented long-term stability, the EM27/SUN qualifies as an useful supplement to the existing TCCON network in remote areas. To achieve consistent performance, such an extension requires careful testing of any spectrometers involved by application of common quality assurance measures. One major aim of the COllaborative Carbon Column Observing Network (COCCON) infrastructure is to provide these services to all EM27/SUN operators. In the framework of COC-CON development, the performance of an ensemble of 30 EM27/SUN spectrometers was tested and found to be very uniform, enhanced by the centralized inspection performed at the Karlsruhe Institute of Technology prior to deployment. Taking into account measured instrumental line shape parameters for each spectrometer, the resulting average bias across the ensemble with respect to the reference EM27/SUN used in the long-term study in XCO 2 is 0.20 ppmv, while it is 0.8 ppbv for XCH 4 . The average standard deviation of the ensemble is 0.13 ppmv for XCO 2 and 0.6 ppbv for XCH 4 . In addition to the robust metric based on absolute differences, we calculate the standard deviation among the empirical calibration factors. The resulting 2σ uncertainty is 0.6 ppmv for XCO 2 and 2.2 ppbv for XCH 4 . As indicated by the executed long-term study on one device presented here, the remaining empirical calibration factor deduced for each individual instrument can be assumed constant over time. Therefore the application of these empirical factors is expected to further improve the EM27/SUN network conformity beyond the scatter among the empirical calibration factors reported above.

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Assessment of errors and biases in retrievals of X<sub>CO<sub>2</sub></sub>, X<sub>CH<sub>4</sub></sub>, X<sub>CO</sub>, and X<sub>N<sub>2</sub>O</sub> from a 0.5 cm<sup>–1</sup> resolution solar-viewing spectrometer

Cited by 55 publications

References 41 publications

Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers

Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers

Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

Building the COllaborative Carbon Column Observing Network (COCCON): long-term stability and ensemble performance of the EM27/SUN Fourier transform spectrometer

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