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

Applied Sciences

卷:11

Astrid Lampert¹  Volker Ebert²  Felix Witt²  Javis Nwaboh²  Henning Bohlius² 

[1] Institut für Flugführung der Technischen Universität Braunschweig, Hermann-Blenk-Str. 27, 38108 Brunswick, Germany;

[2] Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Brunswick, Germany;

关键词: water vapor;    laser spectroscopy;    near-infrared;    dTDLAS;    eddy covariance;   

DOI  :  10.3390/app11115189

来源: DOAJ

【 摘 要 】

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 ${\mathrm{H}}_2\mathrm{O}$ at tropospheric conditions, the newly designed setup fulfills the static precision and accuracy requirements of the proposed airborne EC hygrometer.

【 授权许可】

Unknown