Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers
Recent advances in laser spectroscopy enable high-frequency in situ measurements of the isotope composition of water vapour. At low water vapour mixing ratios, however, the measured stable water isotope composition can be substantially affected by a measurement artefact known as the mixing ratio dep...
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ftdoajarticles:oai:doaj.org/article:4b39d5b288e84f58ac1e7cc2f219a34b 2023-05-15T15:14:34+02:00 Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers Y. Weng A. Touzeau H. Sodemann 2020-06-01T00:00:00Z https://doi.org/10.5194/amt-13-3167-2020 https://doaj.org/article/4b39d5b288e84f58ac1e7cc2f219a34b EN eng Copernicus Publications https://www.atmos-meas-tech.net/13/3167/2020/amt-13-3167-2020.pdf https://doaj.org/toc/1867-1381 https://doaj.org/toc/1867-8548 doi:10.5194/amt-13-3167-2020 1867-1381 1867-8548 https://doaj.org/article/4b39d5b288e84f58ac1e7cc2f219a34b Atmospheric Measurement Techniques, Vol 13, Pp 3167-3190 (2020) Environmental engineering TA170-171 Earthwork. Foundations TA715-787 article 2020 ftdoajarticles https://doi.org/10.5194/amt-13-3167-2020 2023-01-08T01:37:03Z Recent advances in laser spectroscopy enable high-frequency in situ measurements of the isotope composition of water vapour. At low water vapour mixing ratios, however, the measured stable water isotope composition can be substantially affected by a measurement artefact known as the mixing ratio dependency, which is commonly considered independent of the isotope composition. Here we systematically investigate how the mixing ratio dependency, in a range from 500 to 23 000 ppmv of three commercial cavity ring-down spectrometers, is affected by the isotope composition of water vapour. We find that the isotope composition of water vapour has a substantial and systematic impact on the mixing ratio dependency for all three analysers, particularly at mixing ratios below 4000 ppmv. This isotope composition dependency can create a deviation of ±0.5 ‰ and ±6.0 ‰ for δ 18 O and δ D , respectively, at ∼2000 ppmv, resulting in about 2 ‰–3 ‰ deviation for the d -excess. An assessment of the robustness of our findings shows that the overall behaviour is reproducible over up to 2 years for different dry gas supplies, while being independent of the method for generating the water vapour and being the first order of the evaluation sequence. We propose replacing the univariate mixing ratio dependency corrections with a new, combined isotope composition–mixing ratio dependency correction. Using aircraft- and ship-based measurements in an Arctic environment, we illustrate a relevant application of the correction. Based on our findings, we suggest that the dependency on the isotope composition may be primarily related to spectroscopy. Repeatedly characterising the combined isotope composition–mixing ratio dependency of laser spectrometers when performing water vapour measurements at high elevations, on aircraft, or in polar regions appears critical to enable reliable data interpretation in dry environments. Article in Journal/Newspaper Arctic Directory of Open Access Journals: DOAJ Articles Arctic Atmospheric Measurement Techniques 13 6 3167 3190 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental engineering TA170-171 Earthwork. Foundations TA715-787 |
spellingShingle |
Environmental engineering TA170-171 Earthwork. Foundations TA715-787 Y. Weng A. Touzeau H. Sodemann Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
topic_facet |
Environmental engineering TA170-171 Earthwork. Foundations TA715-787 |
description |
Recent advances in laser spectroscopy enable high-frequency in situ measurements of the isotope composition of water vapour. At low water vapour mixing ratios, however, the measured stable water isotope composition can be substantially affected by a measurement artefact known as the mixing ratio dependency, which is commonly considered independent of the isotope composition. Here we systematically investigate how the mixing ratio dependency, in a range from 500 to 23 000 ppmv of three commercial cavity ring-down spectrometers, is affected by the isotope composition of water vapour. We find that the isotope composition of water vapour has a substantial and systematic impact on the mixing ratio dependency for all three analysers, particularly at mixing ratios below 4000 ppmv. This isotope composition dependency can create a deviation of ±0.5 ‰ and ±6.0 ‰ for δ 18 O and δ D , respectively, at ∼2000 ppmv, resulting in about 2 ‰–3 ‰ deviation for the d -excess. An assessment of the robustness of our findings shows that the overall behaviour is reproducible over up to 2 years for different dry gas supplies, while being independent of the method for generating the water vapour and being the first order of the evaluation sequence. We propose replacing the univariate mixing ratio dependency corrections with a new, combined isotope composition–mixing ratio dependency correction. Using aircraft- and ship-based measurements in an Arctic environment, we illustrate a relevant application of the correction. Based on our findings, we suggest that the dependency on the isotope composition may be primarily related to spectroscopy. Repeatedly characterising the combined isotope composition–mixing ratio dependency of laser spectrometers when performing water vapour measurements at high elevations, on aircraft, or in polar regions appears critical to enable reliable data interpretation in dry environments. |
format |
Article in Journal/Newspaper |
author |
Y. Weng A. Touzeau H. Sodemann |
author_facet |
Y. Weng A. Touzeau H. Sodemann |
author_sort |
Y. Weng |
title |
Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
title_short |
Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
title_full |
Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
title_fullStr |
Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
title_full_unstemmed |
Correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
title_sort |
correcting the impact of the isotope composition on the mixing ratio dependency of water vapour isotope measurements with cavity ring-down spectrometers |
publisher |
Copernicus Publications |
publishDate |
2020 |
url |
https://doi.org/10.5194/amt-13-3167-2020 https://doaj.org/article/4b39d5b288e84f58ac1e7cc2f219a34b |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
Atmospheric Measurement Techniques, Vol 13, Pp 3167-3190 (2020) |
op_relation |
https://www.atmos-meas-tech.net/13/3167/2020/amt-13-3167-2020.pdf https://doaj.org/toc/1867-1381 https://doaj.org/toc/1867-8548 doi:10.5194/amt-13-3167-2020 1867-1381 1867-8548 https://doaj.org/article/4b39d5b288e84f58ac1e7cc2f219a34b |
op_doi |
https://doi.org/10.5194/amt-13-3167-2020 |
container_title |
Atmospheric Measurement Techniques |
container_volume |
13 |
container_issue |
6 |
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3167 |
op_container_end_page |
3190 |
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1766345006439727104 |