the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 18 Sep 2024
The Airborne Chicago Water Isotope Spectrometer: An Integrated Cavity Output Spectrometer for Measurements of the HDO/H2O Isotopic Ratio in the Asian Summer Monsoon
Abstract. We describe a new version of the Chicago Water Isotope Spectrometer (ChiWIS), designed for airborne measurements of vapor-phase water isotopologues in the dry upper troposphere and lower stratosphere (UTLS) aboard research aircraft. This version of the instrument is a tunable diode laser (TDL), off-axis integrated cavity output spectrometer (OA-ICOS). The instrument was designed to measure the HDO/H2O ratio in the 2017 Asian Summer Monsoon flight aboard the M-55 Geophysica during the StratoClim campaign, and so far has also flown aboard the WB-57F in the 2021 and 2022 ACCLIP campaigns. The spectrometer scans absorption lines of both H2O and HDO near 2.647 μm wavelength in a single current sweep, and has an effective path length of 7.5 km under optimal conditions. The instrument utilizes a novel non-axially-symmetric optical component which increases the signal-to-noise ratio by a factor of 3. Ultra-polished, 4-inch diameter cavity mirrors suppress scattering losses, maximize mirror reflectivity, and yield optical fringing significantly below typical electrical noise levels. In laboratory conditions, the instrument has demonstrated a 5-second measurement precision of 3.6 ppbv and 82 pptv in H2O and HDO, respectively.
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Status: final response (author comments only)
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RC1: 'Comment on amt-2024-98', Anonymous Referee #3, 24 Sep 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-98/amt-2024-98-RC1-supplement.pdf
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CC1: 'Comment on amt-2024-98', Farahnaz Khosrawi, 22 Oct 2024
You purely describe the instrument here and it is an instrument, as I understand, that is supposed to measure isotopic ratios everywhere in the world. You made your first measurements with this instrument in the Asian summer monsoon since it was the first opportunity where you could apply it. Thus, I would suggest to omit either "in the Asian Summer Monsoon" from the title or somehow make clear in the title that your first application was for measurements in the Asian summer monsoon.
Citation: https://doi.org/10.5194/amt-2024-98-CC1 -
AC1: 'Reply on CC1', Benjamin Clouser, 23 Oct 2024
Thank you for your comment, it is well-received. I debated dropping "in the Asian Summer Monsoon" from the title while preparing the manuscript, but ultimately decided to leave it. On one hand, the instrument was expressly designed to make measurements in the ASM during StratoClim, and made many hours of measurements of monsoon outflow during ACCLIP. On the other hand, from an operational standpoint, conditions in the Asian Monsoon upper troposphere / lower stratosphere are not very different from UT/LS conditions elsewhere so the title may be overly restricting. Maybe it would be better to replace "in the Asian Summer Monsoon" with "in the UT/LS". The coauthors and I will revisit this issue as we revise the manuscript.
Citation: https://doi.org/10.5194/amt-2024-98-AC1
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AC1: 'Reply on CC1', Benjamin Clouser, 23 Oct 2024
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RC2: 'Comment on amt-2024-98', Anonymous Referee #2, 30 Oct 2024
The comment was uploaded in the form of a supplement: https://amt.copernicus.org/preprints/amt-2024-98/amt-2024-98-RC2-supplement.pdf
Data sets
StratoClim Campaign Data StratoClim Team https://halo-db.pa.op.dlr.de/mission/101
ACCLIP Campaign Data ACCLIP Team https://www-air.larc.nasa.gov/cgi-bin/ArcView/acclip
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