scholarly journals Absolute, pressure-dependent validation of a calibration-free, airborne laser hygrometer transfer standard (SEALDH-II) from 5 to 1200 ppmv using a metrological humidity generator

2018 ◽  
Vol 11 (1) ◽  
pp. 459-471 ◽  
Author(s):  
Bernhard Buchholz ◽  
Volker Ebert
Keyword(s):  
Water Vapor ◽  
Mole Fraction ◽  
Absolute Pressure ◽  
Humidity Generator ◽  
Transfer Standard ◽  
Diode Laser Spectrometer ◽  
Comparison Results ◽  
Holistic Concept ◽  
Calibration Free ◽  
Metrological Validation

Abstract. Highly accurate water vapor measurements are indispensable for understanding a variety of scientific questions as well as industrial processes. While in metrology water vapor concentrations can be defined, generated, and measured with relative uncertainties in the single percentage range, field-deployable airborne instruments deviate even under quasistatic laboratory conditions up to 10–20 %. The novel SEALDH-II hygrometer, a calibration-free, tuneable diode laser spectrometer, bridges this gap by implementing a new holistic concept to achieve higher accuracy levels in the field. We present in this paper the absolute validation of SEALDH-II at a traceable humidity generator during 23 days of permanent operation at 15 different H2O mole fraction levels between 5 and 1200 ppmv. At each mole fraction level, we studied the pressure dependence at six different gas pressures between 65 and 950 hPa. Further, we describe the setup for this metrological validation, the challenges to overcome when assessing water vapor measurements on a high accuracy level, and the comparison results. With this validation, SEALDH-II is the first airborne, metrologically validated humidity transfer standard which links several scientific airborne and laboratory measurement campaigns to the international metrological water vapor scale.

scholarly journals SEALDH-II – a calibration-free transfer standard for airborne water vapor measurements: Pressure dependent absolute validation from 5–1200 ppmv at a metrological humidity generator

2017 ◽  
Author(s):  
Bernhard Buchholz ◽  
Volker Ebert
Keyword(s):  
Water Vapor ◽  
The Novel ◽  
Humidity Generator ◽  
Transfer Standard ◽  
Diode Laser Spectrometer ◽  
Comparison Results ◽  
Tuneable Diode Laser ◽  
Calibration Free ◽  
Metrological Validation ◽  
Scientific Questions

Abstract. Highly accurate water vapor measurements are indispensable for understanding a variety of scientific questions as well as industrial processes. While in metrology water vapor concentrations can be defined, generated and measured with relative uncertainties in the single percentage range, field deployable airborne instruments deviate even under quasi-static laboratory conditions up to 10–20 %. The novel SEALDH-II hygrometer, a calibration-free, tuneable diode laser spectrometer, bridges this gap by implementing an entirely new concept to achieve higher accuracy levels in the field. Here we present the absolute validation of SEALDH-II at a traceable humidity generator during 23 days of permanent operation at 15 different H2O concentration levels between 5 and 1200 ppmv. At each concentration level, we studied the pressure dependence at 6 different gas pressures between 65 and 950 hPa. Further, we describe the setup for this metrological validation, the challenges to overcome when assessing water vapor measurements on a high accuracy level, as well as the comparison results. With this validation, SEALDH-II is the first metrologically validated humidity transfer standard which links several scientific airborne and laboratory measurement campaigns to the international metrological water vapor scale.

scholarly journals Characterization and mitigation of water vapor effects in the measurement of ozone by chemiluminescence with nitric oxide

2013 ◽  
Vol 6 (5) ◽  
pp. 9263-9295
Author(s):  
P. Boylan ◽  
D. Helmig ◽  
J.-H. Park
Keyword(s):  
Nitric Oxide ◽  
Water Vapor ◽  
Mole Fraction ◽  
Laboratory Experiments ◽  
High Sensitivity ◽  
Fast Response ◽  
Atmospheric Ozone ◽  
Permeable Membrane ◽  
Signal Correction ◽  
High Sensitivity Detection

Abstract. Laboratory experiments were conducted to investigate the effects of water vapor on the reaction of nitric oxide with ozone in a chemiluminescence instrument used for fast response and high sensitivity detection of atmospheric ozone. Water vapor was introduced into a constant level ozone standard and both ozone and water vapor signals were recorded at 10 Hz. The presence of water vapor was found to reduce, i.e. quench the ozone signal. A correction factor was determined to be 4.15 ± 0.14 × 10−3, which corresponds to a 4.15% increase in the measured ozone signal per 10 mmol mol−1 co-sampled water vapor. An ozone-inert water vapor permeable membrane (Nafion dryer) was installed in the sampling line and was shown to remove the bulk of the water vapor mole fraction in the sample air. At water vapor mole fractions above 25 mmol mol−1, the Nafion dryer removed over 75% of the water vapor in the sample. This reduced the ozone signal correction from over 11% to less than 2.5%. The Nafion dryer was highly effective at reducing the fast fluctuations of the water vapor signal (more than 97%) while leaving the ozone signal unaffected, which is a crucial improvement for minimizing the interference of water vapor fluxes on the ozone flux determination by the eddy covariance technique.

Influence of Vegetation Moisture on Combustion of Pyrolysis Gases in Wildland Fires

2011 ◽  
Author(s):  
Selina C. Dover ◽  
Ambarish R. Dahale ◽  
Babak Shotorban ◽  
Shankar Mahalingam ◽  
David R. Weise
Keyword(s):  
Water Vapor ◽  
Moisture Content ◽  
Mole Fraction ◽  
Flame Structure ◽  
Combustion Process ◽  
Fuel Moisture ◽  
Wildland Fires ◽  
Effect Of Moisture ◽  
Fuel Moisture Content ◽  
Pyrolysis Gases

Since wildland fires occur in living vegetation, the fuel moisture content must be considered in order to correctly predict the behavior of the fire. One facet of combustion of pyrolysis gases that has not been considered in previous research is the effect of moisture on the combustion process. This effect is investigated by using CHEMKIN software to study an opposed diffusion flame model for three pyrolysis fuels relevant to wildfires. The effect of moisture on flame structure is investigated by varying the mole fraction of water vapor in the fuels, with air as oxidizer. In all cases, the flame extinguishes when the water mole fraction is between 0.55 and 0.65. O2 and H are the only components that exhibit a significant change in concentration under these conditions.

A diode-laser spectrometer for measuring ortho/para composition of water vapor

2008 ◽  
Vol 51 (6) ◽  
pp. 894-897 ◽  
Author(s):  
P. O. Kapralov ◽  
V. G. Artemov ◽  
A. M. Makurenkov ◽  
V. I. Tikhonov ◽  
A. A. Volkov
Keyword(s):  
Water Vapor ◽  
Diode Laser ◽  
Laser Spectrometer ◽  
Diode Laser Spectrometer

scholarly journals The rate of water vapor evaporation from ice substrates in the presence of HCl and HBr: implications for the lifetime of atmospheric ice particles

2003 ◽  
Vol 3 (4) ◽  
pp. 1131-1145 ◽  
Author(s):  
C. Delval ◽  
B. Fluckiger ◽  
M. J. Rossi
Keyword(s):  
Activation Energy ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Absorption Spectra ◽  
Mole Fraction ◽  
Rate Constant ◽  
Enthalpy Of Sublimation ◽  
Experimental Uncertainty ◽  
Ice Particles ◽  
Ftir Absorption Spectra

Abstract. Using a multidiagnostic approach the rate Rev [ molec cm-3 s-1] or flux Jev [ molec cm-2 s-1] of evaporation of H2O and its corresponding rate constant for condensation, kcond [s-1 ], on a 1 µm thick ice film have been studied in the temperature range 190 to 240 K as well as in the presence of small amounts of HCl and HBr that left the vapor pressure of H2O on ice unchanged. The resulting Arrhenius expressions for pure ice are Jev = 1.6 · 10 28 ± 1 · exp  (- 10.3 ± 1.2/ RT)  [ molec cm-2 s-1] , kcond = 1.7 · 10 - 2 ± 1 · exp  (+ 1.6 ± 1.5/ RT ) [s -1], in the presence of a HCl mole fraction in the range 3.2 · 10 - 5 - 6.4 · 10 - 3 : Jev = 6.4 · 10 26 ± 1 · exp  (- 9.7 ± 1.2/ RT)  [ molec cm-2 s-1] , kcond = 2.8 · 10 - 2 ± 1 · exp ( + 1.5 ± 1.6 /RT)  [s -1], and a HBr mole fraction smaller than 6.4 · 10 - 3 : Jev = 7.4 · 10 25 ± 1 · exp ( - 9.1 ± 1.2 /RT)  [ molec cm-2 s-1] , kcond = 7.1 · 10 - 5 ± 1 · exp (+ 2.6 ± 1.5/ RT) [s -1]. The small negative activation energy for H2O condensation on ice points to a precursor mechanism. The corresponding enthalpy of sublimation is DHsubl = Eev - Econd = 11.9 ± 2.7 kcal mol-1 , DHsubl = 11.2 ± 2.8 kcal mol-1, and DHsubl = 11.7 ± 2.8 kcal mol-1 whose values are identical within experimental uncertainty to the accepted literature value of 12.3 kcal mol-1 . Interferometric data at 633 nm and FTIR absorption spectra in transmission support the kinetic results. The data are consistent with a significant lifetime enhancement for HCl- and HBr-contaminated ice particles by a factor of 3–6 and 10–20, respectively, for submonolayer coverages of HX once the fraction of the ice not contaminated by HX has evaporated.

scholarly journals Evaluation of supplementary comparison EURAMAT.M.P-S14 in the range 50 MPa to 1 GPa of hydraulic gauge pressure

ACTA IMEKO ◽  
2018 ◽  
Vol 7 (1) ◽  
pp. 76
Author(s):  
Jens Könemann
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Individual Measurement ◽  
Transfer Standard ◽  
Pressure Transducers ◽  
Comparison Results ◽  
Gauge Pressure ◽  
The Individual ◽  
Rich Data ◽  
Almost All

In this work, we present a mathematical procedure to evaluate a hydraulic gauge pressure comparison in the range to 1 GPa piloted by PTB and using a transfer standard consisting of two series of modern high-pressure transducers, i.e. eight pressure transducers in total. This set of parallel arranged transducers should ensure reliability of the transfer standard at high pressures and provide rich data for testing the performance of modern high-pressure transducers. The analysis of the comparison results was based on the evaluation of the individual measurement deviations of these transducers with respect to the laboratory standards, whereas the corresponding comparison reference values and their uncertainty were determined separately at each pressure point and pressure transducer. All these results were summarized to derive the degree of equivalence for each laboratory at each pressure which was found for all laboratories to be consistent at almost all pressures.

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