scholarly journals Photoacoustic hygrometer for icing wind tunnel water content measurement: design, analysis, and intercomparison

2021 ◽  
Vol 14 (3) ◽  
pp. 2477-2500
Author(s):  
Benjamin Lang ◽  
Wolfgang Breitfuss ◽  
Simon Schweighart ◽  
Philipp Breitegger ◽  
Hugo Pervier ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Tunnel ◽  
Water Content ◽  
Measurement Accuracy ◽  
Near Infrared ◽  
Limit Of Detection ◽  
General Description ◽  
Sampling System ◽  
Content Measurement ◽  
Better Than

Abstract. This work describes the latest design, calibration and application of a near-infrared laser diode-based photoacoustic (PA) hygrometer developed for total water content measurement in simulated atmospheric freezing precipitation and high ice water content conditions with relevance in fundamental icing research, aviation testing, and certification. The single-wavelength and single-pass PA absorption cell is calibrated for molar water vapor fractions with a two-pressure humidity generator integrated into the instrument. Laboratory calibration showed an estimated measurement accuracy better than 3.3 % in the water vapor mole fraction range of 510–12 360 ppm (5 % from 250–21 200 ppm) with a theoretical limit of detection (3σ) of 3.2 ppm. The hygrometer is examined in combination with a basic isokinetic evaporator probe (IKP) and sampling system designed for icing wind tunnel applications, for which a general description of total condensed water content (CWC) measurements and uncertainties are presented. Despite the current limitation of the IKP to a hydrometeor mass flux below 90 gm-2s-1, a CWC measurement accuracy better than 20 % is achieved by the instrument above a CWC of 0.14 g m−3 in cold air (−30 ∘C) with suitable background humidity measurement. Results of a comparison to the Cranfield University IKP instrument in freezing drizzle and rain show a CWC agreement of the two instruments within 20 %, which demonstrates the potential of PA hygrometers for water content measurement in atmospheric icing conditions.

scholarly journals Photoacoustic hygrometer for icing wind tunnel water content measurement: Design, analysis and intercomparison

2020 ◽  
Author(s):  
Benjamin Lang ◽  
Wolfgang Breitfuss ◽  
Simon Schweighart ◽  
Philipp Breitegger ◽  
Hugo Pervier ◽  
...  
Keyword(s):  
Water Vapor ◽  
Wind Tunnel ◽  
Water Content ◽  
Measurement Accuracy ◽  
Near Infrared ◽  
Limit Of Detection ◽  
General Description ◽  
Sampling System ◽  
Content Measurement ◽  
Better Than

Abstract. This work describes the latest design, calibration and application of a near-infrared laser diode-based photoacoustic (PA) hygrometer, developed for total water content measurement in simulated atmospheric freezing precipitation and high ice water content conditions with relevance in fundamental icing research, as well as aviation testing and certification. The single-wavelength and single-pass PA absorption cell is calibrated for molar water vapor fractions with a two-pressure humidity generator integrated into the instrument. Laboratory calibration showed an estimated measurement accuracy better than 3.3 % in the water vapor mole fraction range of 510–12,360 ppm (5 % from 250–21,200 ppm) with a theoretical limit of detection (3 sigma) of 3.2 ppm. The hygrometer is examined in combination with a basic isokinetic evaporator probe (IKP) and sampling system designed for icing wind tunnel application, for which a general description of total condensed water content (CWC) measurement and uncertainties are presented. Despite the current limitation of the IKP to a hydrometeor mass flux below 90 g m−2 s−1, a CWC measurement accuracy better than 20 % is achieved by the instrument above a CWC of 0.14 g m−3 in cold air (−30 °C) with suitable background humidity measurement. Results of a comparison to the Cranfield University IKP instrument in freezing drizzle and rain show a CWC agreement of the two instruments within 20 %, which demonstrates the potential of PA hygrometers for water content measurement in atmospheric icing conditions.

scholarly journals Calibration and Uncertainty Estimation for Water Content Measurement in Solids

2021 ◽  
Vol 42 (3) ◽  
Author(s):  
Rudolf Aro ◽  
Mohamed Wajdi Ben Ayoub ◽  
Ivo Leito ◽  
Éric Georgin ◽  
Benoit Savanier
Keyword(s):  
Water Vapor ◽  
Water Content ◽  
Software Tool ◽  
Uncertainty Estimation ◽  
Multiple Point ◽  
Content Measurement ◽  
Analysis Technique ◽  
Calibration Methods ◽  
Vapor Analysis ◽  
Secondary Methods

AbstractIn the field of water content measurement, the calibration of coulometric methods (e.g., coulometric Karl Fischer titration or evolved water vapor analysis) is often overlooked. However, as coulometric water content measurement methods are used to calibrate secondary methods, their results must be obtained with the highest degree of confidence. The utility of calibrating such instruments has been recently demonstrated. Both single and multiple point calibration methods have been suggested. This work compares these calibration methods for the evolved water vapor analysis technique. Two uncertainty estimation approaches (Kragten’s spreadsheet and M-CARE software tool) were compared as well, both based on the ISO GUM method.

scholarly journals A fiber-coupled laser hygrometer for airborne total water measurement

2014 ◽  
Vol 7 (1) ◽  
pp. 215-223 ◽  
Author(s):  
S. W. Dorsi ◽  
L. E. Kalnajs ◽  
D. W. Toohey ◽  
L. M. Avallone
Keyword(s):  
Water Vapor ◽  
Water Content ◽  
Diode Laser ◽  
Near Infrared ◽  
Tunable Diode Laser ◽  
Infrared Light ◽  
Closed Path ◽  
Total Water ◽  
University Of Colorado ◽  
Condensed Water

Abstract. The second-generation University of Colorado closed-path tunable-diode laser hygrometer (CLH-2) is an instrument for the airborne in situ measurement of total water content – the sum of vapor-, liquid- and ice-phase water – in clouds. This compact instrument has been flown on the NSF/NCAR Gulfstream-V aircraft in an underwing canister. It operates autonomously and uses fiber-coupled optics to eliminate the need for a supply of dry compressed gas. In operation, sample air is ingested into a forward-facing sub-isokinetic inlet; this sampling configuration results in particle concentrations that are enhanced relative to ambient and causes greater instrument sensitivity to condensed water particles. Heaters within the inlet vaporize the ingested water particles, and the resulting augmented water vapor mixing ratio is measured by absorption of near-infrared light in a single-pass optical cell. The condensed water content is then determined by subtracting the ambient water vapor content from the total and by accounting for the inertial enhancement of particles into the sampling inlet. The CLH-2 is calibrated in the laboratory over a range of pressures and water vapor mixing ratios; the uncertainty in CLH-2 condensed water retrievals is estimated to be 14.3% to 16.1% (1-σ). A vapor-only laboratory intercomparison with the first-generation University of Colorado closed-path tunable-diode laser hygrometer (CLH) shows agreement within the 2-σ uncertainty bounds of both instruments.

scholarly journals Intercomparison of atmospheric water vapor soundings from the differential absorption lidar (DIAL) and the solar FTIR system on Mt. Zugspitze

2011 ◽  
Vol 4 (5) ◽  
pp. 835-841 ◽  
Author(s):  
H. Vogelmann ◽  
R. Sussmann ◽  
T. Trickl ◽  
T. Borsdorff
Keyword(s):  
Water Vapor ◽  
Near Infrared ◽  
Integration Time ◽  
Research Station ◽  
Horizontal Distance ◽  
Differential Absorption ◽  
Differential Absorption Lidar ◽  
The Mean ◽  
The Difference ◽  
Better Than

Abstract. We present an intercomparison of three years of measurements of integrated water vapor (IWV) performed by the mid-infrared solar FTIR (Fourier Transform Infra-Red) instrument on the summit of Mt. Zugspitze (2964 m a.s.l.) and by the nearby near-infrared differential absorption lidar (DIAL) at the Schneefernerhaus research station (2675 m a.s.l.). The solar FTIR was shown to be one of the most accurate and precise IWV sounders in recent work (Sussmann et al., 2009) and is taken as the reference here. By calculating the FTIR-DIAL correlation (22 min coincidence interval, 15 min integration time) we derive an almost ideal slope of 0.996 (10), a correlation coefficient of R = 0.99, an IWV intercept of −0.039 (42) mm (−1.2 % of the mean), and a bias of −0.052 (26) mm (−1.6 % of the mean) from the scatter plot. By selecting a subset of coincidences with an optimum temporal and spatial matching between DIAL and FTIR, we obtain a conservative estimate of the precision of the DIAL in measuring IWV which is better than 0.1 mm (3.2 % of the mean). We found that for a temporal coincidence interval of 22 min the difference in IWV measured by these two systems is dominated by the volume mismatch (horizontal distance: 680 m). The outcome from this paper is twofold: (1) the IWV soundings by FTIR and DIAL agree very well in spite of the differing wavelength regions with different spectroscopic line parameters and retrieval algorithms used. (2) In order to derive an estimate of the precision of state-of-the-art IWV sounders from intercomparison experiments, it is necessary to use a temporal matching on time scales shorter than 10 min and a spatial matching on the 100-m scale.

scholarly journals Intercomparison of atmospheric water vapor soundings from the differential absorption lidar (DIAL) and the solar FTIR system on Mt. Zugspitze

2010 ◽  
Vol 3 (6) ◽  
pp. 5411-5428 ◽  
Author(s):  
H. Vogelmann ◽  
R. Sussmann ◽  
T. Trickl ◽  
T. Borsdorff
Keyword(s):  
Water Vapor ◽  
Near Infrared ◽  
Integration Time ◽  
Research Station ◽  
Horizontal Distance ◽  
Differential Absorption ◽  
Differential Absorption Lidar ◽  
The Mean ◽  
The Difference ◽  
Better Than

Abstract. We present an intercomparison of three years of measurements of integrated water vapor (IWV) performed by the mid-infrared solar FTIR instrument on the summit of Mt. Zugspitze (2964 m a.s.l.) and the nearby near-infrared differential absorption lidar (DIAL) at the Schneefernerhaus research station (UFS, 2675 m a.s.l.). The solar FTIR turned out to be one of the most accurate and precise IWV sounders in recent work (Sussmann et al., 2009) and is taken as the reference here. By calculating the FTIR-DIAL correlation (22 min coincidence interval, 15 min integration time) we derive an almost ideal slope of 0.99(1), a correlation coefficient of R = 0.99, an IWV intercept of 0.056(42) mm (1.8% of the mean), and a bias of 0.097(26) mm (3.1% of the mean) from the scatter plot. By selecting a subset of coincidences with an optimum temporal and spatial matching between DIAL and FTIR, we obtain a conservative estimate of the precision of the DIAL in measuring IWV which is better than 0.1 mm (3.2% of the mean). We found that for a temporal coincidence interval of 22 min the difference in IWV measured by these two systems is dominated by the volume mismatch (horizontal distance: 680 m). The outcome from this paper is twofold: (1) The IWV soundings by FTIR and DIAL agree very well in spite of the differing wavelength regions with different spectroscopic line parameters and retrieval algorithms used. (2) In order to derive an estimate of the precision of state-of-the-art IWV sounders from intercomparison experiments, it is necessary to use a temporal matching on the shorter 10-min scale and a spatial matching on the smaller 1-km scale.

scholarly journals New Gridded Product for the Total Columnar Atmospheric Water Vapor over Ocean Surface Constructed from Microwave Radiometer Satellite Data

2021 ◽  
Vol 13 (12) ◽  
pp. 2402
Author(s):  
Weifu Sun ◽  
Jin Wang ◽  
Yuheng Li ◽  
Junmin Meng ◽  
Yujia Zhao ◽  
...  
Keyword(s):  
Water Vapor ◽  
Microwave Radiometer ◽  
Atmospheric Water Vapor ◽  
Global Ocean ◽  
Optimal Interpolation ◽  
Fusion Product ◽  
Mean Deviation ◽  
Atmospheric Water ◽  
Absolute Deviation ◽  
Better Than

Based on the optimal interpolation (OI) algorithm, a daily fusion product of high-resolution global ocean columnar atmospheric water vapor with a resolution of 0.25° was generated in this study from multisource remote sensing observations. The product covers the period from 2003 to 2018, and the data represent a fusion of microwave radiometer observations, including those from the Special Sensor Microwave Imager Sounder (SSMIS), WindSat, Advanced Microwave Scanning Radiometer for Earth Observing System sensor (AMSR-E), Advanced Microwave Scanning Radiometer 2 (AMSR2), and HY-2A microwave radiometer (MR). The accuracy of this water vapor fusion product was validated using radiosonde water vapor observations. The comparative results show that the overall mean deviation (Bias) is smaller than 0.6 mm; the root mean square error (RMSE) and standard deviation (SD) are better than 3 mm, and the mean absolute deviation (MAD) and correlation coefficient (R) are better than 2 mm and 0.98, respectively.

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