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

被引:6
作者
Witt, Felix [1 ]
Nwaboh, Javis [1 ]
Bohlius, Henning [1 ]
Lampert, Astrid [2 ]
Ebert, Volker [1 ,3 ]
机构
[1] Phys Tech Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Germany
[2] Techn Univ Braunschweig, Inst Flugfuhrung, Hermann Blenk Str 27, D-38108 Braunschweig, Germany
[3] Tech Univ Darmstadt, Dept Mech Engn, React Flows & Diagnost, Otto Berndt Str 3, D-64287 Darmstadt, Germany
来源
APPLIED SCIENCES-BASEL | 2021年 / 11卷 / 11期
关键词
water vapor; laser spectroscopy; near-infrared; dTDLAS; eddy covariance; WATER-VAPOR MEASUREMENTS; TDLAS-HYGROMETER; DUAL-CHANNEL; FLUX; FLUCTUATIONS; PERFORMANCE; CALIBRATION; ABSOLUTE; DESIGN; SETUP;
D O I
10.3390/app11115189
中图分类号
O6 [化学];
学科分类号
0703 ;
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 H2O at tropospheric conditions, the newly designed setup fulfills the static precision and accuracy requirements of the proposed airborne EC hygrometer.
引用
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页数:10
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