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Towards a Fast, Open-Path Laser Hygrometer for Airborne Eddy Covariance Measurements

Witt, Felix ; Nwaboh, Javis ; Bohlius, Henning ; Lampert, Astrid ; Ebert, Volker (2024)
Towards a Fast, Open-Path Laser Hygrometer for Airborne Eddy Covariance Measurements.
In: Applied Sciences, 2021, 11 (11)
doi: 10.26083/tuprints-00019544
Article, Secondary publication, Publisher's Version

Copyright Information: CC BY 4.0 International - Creative Commons, Attribution.

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Item Type: Article
Type of entry: Secondary publication
Title: Towards a Fast, Open-Path Laser Hygrometer for Airborne Eddy Covariance Measurements
Language: English
Date: 15 January 2024
Place of Publication: Darmstadt
Year of primary publication: 2021
Place of primary publication: Basel
Publisher: MDPI
Journal or Publication Title: Applied Sciences
Volume of the journal: 11
Issue Number: 11
Collation: 10 Seiten
DOI: 10.26083/tuprints-00019544
Corresponding Links:
Origin: Secondary publication DeepGreen

Water vapor fluxes play a key role in the energy budget of the atmosphere, and better flux measurements are needed to improve our understanding of the formation of clouds and storms. Large-scale measurements of these fluxes are possible by employing the eddy correlation (EC) method from an aircraft. A hygrometer used for such measurements needs to deliver a temporal resolution of at least 10 Hz while reliably operating in the harsh conditions on the exterior of an aircraft. Here, we present a design concept for a calibration-free, first-principles, open-path dTDLAS hygrometer with a planar, circular and rotationally symmetric multipass cell with new, angled coupling optics. From our measurements, the uncertainty of the instrument is estimated to be below 4.5% (coverage factor k = 1). A static intercomparison between a dTDLAS prototype of the new optics setup and a traceable dew point mirror hygrometer was conducted and showed a systematic relative deviation of 2.6% with a maximal relative error of 2.2%. Combined with a precision of around 1 ppm H₂O at tropospheric conditions, the newly designed setup fulfills the static precision and accuracy requirements of the proposed airborne EC hygrometer.

Uncontrolled Keywords: water vapor, laser spectroscopy, near-infrared, dTDLAS, eddy covariance
Status: Publisher's Version
URN: urn:nbn:de:tuda-tuprints-195448
Additional Information:

This article belongs to the Special Issue Diode Laser Spectroscopy – Robust Sensing for Environmental and Industrial Applications

Classification DDC: 500 Science and mathematics > 530 Physics
600 Technology, medicine, applied sciences > 620 Engineering and machine engineering
Divisions: 16 Department of Mechanical Engineering > Institute of Reactive Flows and Diagnostics (RSM)
Date Deposited: 15 Jan 2024 13:33
Last Modified: 12 Mar 2024 15:10
SWORD Depositor: Deep Green
URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/19544
PPN: 516177516
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