Journal articles: 'Hygrometers'

1

Stroup, William H., James T. Peeler, and Kent Smith. "Evaluation Of Precision Estimates For Fiber-Dimensional And Electrical Hygrometers For Water Activity Determinations." Journal of AOAC INTERNATIONAL 70, no. 6 (November 1, 1987): 955–57. http://dx.doi.org/10.1093/jaoac/70.6.955.

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Abstract The precision of instruments used in 3 collaborative studies conducted within the Food and Drug Administration over a 4-year period (1981, 1982, 1984) for water activity (a„) determinations according to the official AOAC method is evaluated. Calibration responses of the instruments were tested for linearity over the a„ range from 0.75 to 0.97. Average absolute percent difference between predicted and assigned a, values for the linear model ranged from 0.3 to 0.7% for a fiber-dimensional hygrometer (Abbeon) and 3 electrical hygrometers (Beckman, Rotronics, and Weather Measure). The calibration responses for another electrical hygrometer (Hygrodynamics) were nonlinear. The fiber-dimensional hygrometer yielded mean a„ values and precision estimates that did not differ significantly from those obtained with the electrical hygrometers for (NH4)2S04 slush, KN03 slush, sweetened condensed milk, pancake syrup, and cheese spread. However, the mean a„ value for a soy sauce was 0.838 for the electrical hygrometers compared with 0.911 for the fiber-dimensional hygrometer. The fiber-dimensional hygrometer was affected by a volatile components) in the soy sauce that caused an erroneously high a„ value. Pooled estimates of reproducibility (5X) in the 3 studies were 0.008 for the fiber-dimensional hygrometer and 0.010 for the electrical hygrometers; these values were not significantly different from those reported in the study that verified the current official AOAC method.

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Foken, T., and H. Falke. "Technical Note: Calibration instrument for the krypton hygrometer KH20." Atmospheric Measurement Techniques Discussions 5, no. 1 (February 17, 2012): 1695–715. http://dx.doi.org/10.5194/amtd-5-1695-2012.

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Abstract. A calibration instrument for krypton hygrometers (KH20, Campbell Sci.) with variable path length is presented. This unit allows for in-situ calibrations of the krypton hygrometer, which is typically not very stable over time, during measuring campaigns. It was constructed mainly for application at high altitudes and low temperatures, where further improvements are needed to the IR-hygrometers which are normally used. The changing path length requires that a changing concentration of the absorber be simulated. Because oxygen absorbs more strongly than water vapour, the calibration is made against oxygen and transferred to water vapour. The design of the calibration instrument is made as one unit containing a stepper motor system, PC and humidity sensor. For the calibration, it is necessary to install the krypton hygrometer on this unit.

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Foken, T., and H. Falke. "Technical Note: Calibration device for the krypton hygrometer KH20." Atmospheric Measurement Techniques 5, no. 8 (August 1, 2012): 1861–67. http://dx.doi.org/10.5194/amt-5-1861-2012.

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Abstract. A calibration device for krypton hygrometers (KH20, Campbell Scientific, Inc.) with variable path length is presented. This unit allows for in-situ calibrations of the krypton hygrometer, which is typically not very stable over time, during measuring campaigns. It was constructed mainly for application at high altitudes and low temperatures, where further improvements are needed to the IR-hygrometers which are normally used. The changing path length requires that a changing concentration of the absorber be simulated. Because oxygen absorbs more strongly than water vapour, the calibration is made against oxygen and transferred to water vapour. The design of the calibration instrument is made as one unit containing a stepper motor system, PC and humidity sensor. For the calibration, it is necessary to install the krypton hygrometer on this unit.

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Vance, A. K., S. J. Abel, R. J. Cotton, and A. M. Woolley. "Performance of WVSS-II hygrometers on the FAAM research aircraft." Atmospheric Measurement Techniques 8, no. 3 (March 28, 2015): 1617–25. http://dx.doi.org/10.5194/amt-8-1617-2015.

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Abstract. We compare the performance of five hygrometers fitted to the Facility for Airborne Atmospheric Measurement's (FAAM) BAe 146-301 research aircraft using data from approximately 100 flights executed over the course of 2 years under a wide range of conditions. Bulk comparison of cloud free data show good agreement between chilled mirror hygrometers and a WVSS-II fed from a modified Rosemount inlet, but that a WVSS-II fed from the standard flush inlet appears to over-read compared to the other instruments, except at higher humidities. Statistical assessment of hygrometer performance in cloudy conditions is problematic due to the variable nature of clouds, so a number of case studies are used instead to investigate the performance of the hygrometers in sub-optimal conditions. It is found that the flush inlet is not susceptible to either liquid or solid water but that the Rosemount inlet has a significant susceptibility to liquid water and may also be susceptible to ice. In all conditions the WVSS-II responds much more rapidly than the chilled mirror devices, with the flush inlet-fed WVSS-II being more rapid than that connected to the Rosemount.

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Vance, A. K., S. J. Abel, R. J. Cotton, and A. M. Woolley. "Performance of WVSS-II hygrometers on the FAAM Research Aircraft." Atmospheric Measurement Techniques Discussions 7, no. 8 (August 19, 2014): 8643–67. http://dx.doi.org/10.5194/amtd-7-8643-2014.

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Abstract. We compare the performance of five hygrometers fitted to the Facility for Airborne Atmospheric Measurement's (FAAM) BAe 146-301 research aircraft using data from approximately one hundred flights executed over the course of two years under a wide range of conditions. Bulk comparison of cloud free data show good agreement between chilled mirror hygrometers and a WVSS-II fed from a modified Rosemount inlet but that a WVSS-II fed from the standard flush inlet appears to over read compared to the other instruments, except at higher humidities. Statistical assessment of hygrometer performance in cloudy conditions is problematic due to the variable nature of clouds, so a number of case studies are used instead to investigate the performance of the hygrometers in sub optimal conditions. It is found that the flush inlet is not susceptible to either liquid or solid water but that the Rosemount inlet has a significant susceptibility to liquid water; it is not susceptible to ice. In all conditions the WVSS-II respond much more rapidly than the chilled mirror devices, with the flush inlet-fed WVSS-II being more rapid than that connected to the Rosemount.

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6

Meyer, J., C. Rolf, C. Schiller, S. Rohs, N. Spelten, A. Afchine, M. Zöger, et al. "Two decades of water vapor measurements with the FISH fluorescence hygrometer: a review." Atmospheric Chemistry and Physics Discussions 15, no. 5 (March 12, 2015): 7735–82. http://dx.doi.org/10.5194/acpd-15-7735-2015.

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Abstract. The Fast In-situ Stratospheric Hygrometer (FISH) is an airborne Lyman-α photofragment fluorescence hygrometer for accurate and precise measurement of total water mixing ratios (WMR) (gas phase + evaporated ice) in the upper troposphere and lower stratosphere (UT/LS) since almost two decades. Here, we present a comprehensive review of the measurement technique, calibration procedure, accuracy and reliability of FISH. A crucial part for the FISH measurement quality is the regular calibration to a water vapor reference, namely the commercial frostpoint hygrometer DP30. In the frame of this work this frostpoint hygrometer is compared to German and British traceable metrological water standards and its accuracy is found to be 2–4%. Overall, in the range from 4–1000 ppmv, the total accuracy of FISH was found to be 6–8% as stated also in previous publications. For lower mixing ratios down to 1 ppmv, the uncertainty reaches a lower limit of 0.3 ppmv. For specific, non-atmospheric conditions, as set in experiments at the AIDA chamber – namely mixing ratios below 10 and above 100 ppmv in combination with high and low pressure conditions – the need to apply a modified FISH calibration evaluation has been identified. The new evaluation improves the agreement of FISH with other hygrometers to ± 10% accuracy in the respective mixing ratio ranges. Further, a quality check procedure for high total water measurements in cirrus clouds at high pressures (400–500 hPa) is introduced. The performance of FISH in the field is assessed by reviewing intercomparisons of FISH water vapor data with other in-situ and remote sensing hygrometers over the last two decades. We find that the agreement of FISH with the other hygrometers has improved over that time span from overall up to ±30% or more to about ±5–20% @ < 10 ppmv and to ±0–15% @ > 10 ppmv. As presented here, the robust and continuous calibration and operation procedures of the FISH instrument over the last two decades, establish the position of FISH as one of the core instruments for in-situ observations of water vapor in the UT/LS.

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Meyer, J., C. Rolf, C. Schiller, S. Rohs, N. Spelten, A. Afchine, M. Zöger, et al. "Two decades of water vapor measurements with the FISH fluorescence hygrometer: a review." Atmospheric Chemistry and Physics 15, no. 14 (July 30, 2015): 8521–38. http://dx.doi.org/10.5194/acp-15-8521-2015.

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Abstract. For almost two decades, the airborne Fast In-situ Stratospheric Hygrometer (FISH) has stood for accurate and precise measurements of total water mixing ratios (WMR, gas phase + evaporated ice) in the upper troposphere and lower stratosphere (UT/LS). Here, we present a comprehensive review of the measurement technique (Lyman-α photofragment fluorescence), calibration procedure, accuracy and reliability of FISH. Crucial for FISH measurement quality is the regular calibration to a water vapor reference, namely the commercial frost-point hygrometer DP30. In the frame of this work this frost-point hygrometer is compared to German and British traceable metrological water standards and its accuracy is found to be 2–4 %. Overall, in the range from 4 to 1000 ppmv, the total accuracy of FISH was found to be 6–8 %, as stated in previous publications. For lower mixing ratios down to 1 ppmv, the uncertainty reaches a lower limit of 0.3 ppmv. For specific, non-atmospheric conditions, as set in experiments at the AIDA chamber – namely mixing ratios below 10 and above 100 ppmv in combination with high- and low-pressure conditions – the need to apply a modified FISH calibration evaluation has been identified. The new evaluation improves the agreement of FISH with other hygrometers to ± 10 % accuracy in the respective mixing ratio ranges. Furthermore, a quality check procedure for high total water measurements in cirrus clouds at high pressures (400–500 hPa) is introduced. The performance of FISH in the field is assessed by reviewing intercomparisons of FISH water vapor data with other in situ and remote sensing hygrometers over the last two decades. We find that the agreement of FISH with the other hygrometers has improved over that time span from overall up to ± 30 % or more to about ± 5–20 % @ < 10 ppmv and to ± 0–15 % @ > 10 ppmv. As presented here, the robust and continuous calibration and operation procedures of the FISH instrument over the last two decades establish the position of FISH as one of the core instruments for in situ observations of water vapor in the UT/LS.

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8

Moiz, S. A., Kh S. Karimov, and N. D. Gohar. "Orange Dye Thin Film Resistive Hygrometers." Eurasian Chemico-Technological Journal 6, no. 3 (July 13, 2017): 179. http://dx.doi.org/10.18321/ectj609.

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An investigation on electrical properties of organic semiconductor, Orange Dye (OD), C17H17N5O2, resistive hygrometers was made in present study. Organic thin films were deposited on substrate by different thin film deposition methods, such as by vacuum evaporation method (Aluminum/Orange Dye/Aluminum), by spin-coater method from solution (Gold/Orange Dye/Gold), and in normal gravity condition by placing drops of OD solutions over the surface of tissue paper (Tin metal/Orange Dye in tissue paper/Net metal). As OD is also temperature sensitive, that is why to compensate temperature effect for the measurement of humidity dependent electrical properties, special arrangement was provided over the same substrate, but encapsulated from humidity environment. The AC (frequency of 10 Hz) and DC resistances were evaluated from current-voltage characteristics of all samples of resistive hygrometers, measured in the temperature interval range of 20-70 °C and relative humidity range of 30-80%. It was observed that the resistance of the OD decreases with a rise in temperature. Similarly, OD resistance is observed to decrease with increase in humidity level. The relative resistance ratio to relative humidity was found 30 and 12 for the samples deposited by vacuum evaporation and from solution by spin coater respectively. Humidity dependent on electrical properties of these resistive hygrometer make them attractive for use in development of industrial humidity meters.

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9

Yang, Ju, Hong Yi, Zhangyuan Li, and Changqing Ren. "Automatic calibration system of thermo-hygrometers." Journal of Physics: Conference Series 2554, no. 1 (July 1, 2023): 012002. http://dx.doi.org/10.1088/1742-6596/2554/1/012002.

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Abstract Machine vision technology is an interdisciplinary subject involving plenty of fields such as artificial intelligence, neurobiology, psychophysics, computer science, image processing and pattern recognition, etc. In recent years, with rapid development of the technology, machine vision recognition is widely used in many fields of detection and control. For thermo-hygrometers calibration, the manual operation method is used traditionally. This has proven to be a cumbersome, time-consuming, and error-prone activity, as there are lots of models and quantities of thermo-hygrometers to be calibrated. Therefore, an automatic thermo-hygrometers calibration system was developed by using vision recognition technology in combination with automatic movement control as well as a purposely structured database management software. It can complete the calibration and the verification task accurately, timely and efficiently. It has drastically reduced the workload, improved accuracy, and realized the automatic calibration of the thermo-hygrometers.

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10

Tsirlin, O. V., and A. A. Yushkin. "Calibrating electrical sorption hygrometers." Measurement Techniques 30, no. 2 (February 1987): 204–6. http://dx.doi.org/10.1007/bf00865882.

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11

Rollins, A. W., T. D. Thornberry, R. S. Gao, B. D. Hall, and D. W. Fahey. "Catalytic oxidation of H2 on platinum: a method for in situ calibration of hygrometers." Atmospheric Measurement Techniques Discussions 4, no. 3 (May 24, 2011): 3083–95. http://dx.doi.org/10.5194/amtd-4-3083-2011.

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Abstract. Standard reference samples of water vapor suitable for in situ calibration of atmospheric hygrometers are not currently widespread, leading to difficulties in unifying the calibrations of these hygrometers and potentially contributing to measurement discrepancies. We describe and evaluate a system for reliably and quantitatively converting mixtures of H2 in air to H2O on a heated platinum (Pt) surface, providing a compact, portable, adjustable source of water vapor. The technique is shown to be accurate and can be used to easily and predictably produce a wide range of water vapor concentrations (≈1 ppm−2 %) on demand. The result is a H2O standard that is suitable for in situ calibration of hygrometers, with an accuracy nearly that of the available H2 standards (≈±2 %).

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12

Rollins, A. W., T. D. Thornberry, R. S. Gao, B. D. Hall, and D. W. Fahey. "Catalytic oxidation of H2 on platinum: a robust method for generating low mixing ratio H2O standards." Atmospheric Measurement Techniques 4, no. 10 (October 4, 2011): 2059–64. http://dx.doi.org/10.5194/amt-4-2059-2011.

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Abstract. Standard reference samples of water vapor suitable for in situ calibration of atmospheric hygrometers are not currently widespread, leading to difficulties in unifying the calibrations of these hygrometers and potentially contributing to observed measurement discrepancies. We describe and evaluate a system for reliably and quantitatively converting mixtures of H2 in air to H2O on a heated platinum surface, providing a compact, portable, adjustable source of water vapor. The technique is shown to be accurate and can be used to easily and reliably produce a wide range of water vapor concentrations (≈1 ppm −2%) on demand. The result is a H2O standard that is expected to be suitable for in situ calibration of aircraft hygrometers, with an accuracy nearly that of the available H2 standards (≈±2%).

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13

Robens, E., C. H. Massen, and J. J. Hardon. "Studies on historical gravimetric hygrometers." Thermochimica Acta 235, no. 1 (April 1994): 125–33. http://dx.doi.org/10.1016/0040-6031(94)80090-1.

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14

Kiefer, Michael, Dale F. Hurst, Gabriele P. Stiller, Stefan Lossow, Holger Vömel, John Anderson, Faiza Azam, et al. "The SPARC water vapour assessment II: biases and drifts of water vapour satellite data records with respect to frost point hygrometer records." Atmospheric Measurement Techniques 16, no. 19 (October 12, 2023): 4589–642. http://dx.doi.org/10.5194/amt-16-4589-2023.

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Abstract. Satellite data records of stratospheric water vapour have been compared to balloon-borne frost point hygrometer (FP) profiles that are coincident in space and time. The satellite data records of 15 different instruments cover water vapour data available from January 2000 through December 2016. The hygrometer data are from 27 stations all over the world in the same period. For the comparison, real or constructed averaging kernels have been applied to the hygrometer profiles to adjust them to the measurement characteristics of the satellite instruments. For bias evaluation, we have compared satellite profiles averaged over the available temporal coverage to the means of coincident FP profiles for individual stations. For drift determinations, we analysed time series of relative differences between spatiotemporally coincident satellite and hygrometer profiles at individual stations. In a synopsis we have also calculated the mean biases and drifts (and their respective uncertainties) for each satellite record over all applicable hygrometer stations in three altitude ranges (10–30 hPa, 30–100 hPa, and 100 hPa to tropopause). Most of the satellite data have biases <10 % and average drifts <1 % yr−1 in at least one of the respective altitude ranges. Virtually all biases are significant in the sense that their uncertainty range in terms of twice the standard error of the mean does not include zero. Statistically significant drifts (95 % confidence) are detected for 35 % of the ≈ 1200 time series of relative differences between satellites and hygrometers.

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Carvajal, Sergio A., and Ciro A. Sánchez. "Temperature effect in the calibration of capacitive humidity sensors." International Journal of Metrology and Quality Engineering 9 (2018): 9. http://dx.doi.org/10.1051/ijmqe/2018010.

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Capacitive hygrometers are widely used in industrial and environmental measurements. One of the limitations of these sensors is their temperature dependence. While in temperatures beyond 50 °C the effect has been proven to be significant, for standard conditions in calibration laboratories the magnitude of this dependence has not been rigorously studied. This paper presents the analysis and results of a study of the temperature influence in the calibration of capacitive hygrometers designed for monitoring environmental conditions. Ninety measurements were taken on 15 models of capacitive hygrometers using a two-pressure humidity generator between 30%rh and 80%rh and temperatures from 20 to 30 °C. A three-way analysis of variance (ANOVA) was used to evaluate the data. The results show that the calibration correction is independent of the temperature for the conditions considered; however, there is a correlation between the temperature and the devices, indicating that the gradients in temperature affect each technology of fabrication in a different way.

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Chung, Jun Young, Hunter King, and L. Mahadevan. "Evaporative microclimate driven hygrometers and hygromotors." EPL (Europhysics Letters) 107, no. 6 (September 1, 2014): 64002. http://dx.doi.org/10.1209/0295-5075/107/64002.

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Karimov, Kh S., M. Shahid, and S. A. Moiz. "Orange Dye Thin Film Electrochemical Hygrometers." Eurasian Chemico-Technological Journal 7, no. 2 (July 13, 2017): 85. http://dx.doi.org/10.18321/ectj619.

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Electrochemical hygrometers have been fabricated using orange dye (OD) C17H17N5O2 thin films, deposited from aqueous solution under normal conditions. The films were deposited on zinc substrates from 10 wt.% solution of OD in distilled water. These films were than used to make samples of Zn/OD-TP/Cu, Zn/OD/Cu and Zn/OD/Graphite (TP stands for tissue paper); copper electrode was used in the form of a mesh and the graphite in the form of a porous solid. Properties of the samples were investigated in a range of 46-78% humidity. Output voltage and current of the sensors were monitored in electrochemical mode of operation, showing a rise of 8 and 100 times, respectively, with an increase in humidity. These electrochemical hygrometers may be potentially useful for developing humidity meters.

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18

Mestayer, P., and C. Rebattet. "Temperature Sensitivity of Lyman-Alpha Hygrometers." Journal of Atmospheric and Oceanic Technology 2, no. 4 (December 1985): 656–64. http://dx.doi.org/10.1175/1520-0426(1985)002<0656:tsolah>2.0.co;2.

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19

Huang, Jianhua. "A new method for calibrating hygrometers." Review of Scientific Instruments 88, no. 4 (April 2017): 045107. http://dx.doi.org/10.1063/1.4979705.

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Kovaleva, A. A., R. I. Saitov, A. S. Zaporozhets, and E. G. Parfenova. "Method for Calibrating Commercial Microwave Hygrometers." Measurement Techniques 60, no. 3 (June 2017): 305–8. http://dx.doi.org/10.1007/s11018-017-1191-6.

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Högström, R., J. Salminen, and M. Heinonen. "Calibration of hygrometers at non-static conditions." Measurement Science and Technology 31, no. 3 (December 20, 2019): 034003. http://dx.doi.org/10.1088/1361-6501/ab56a6.

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Symons, G. J. "A contribution to the history of hygrometers." Quarterly Journal of the Royal Meteorological Society 7, no. 39 (July 6, 2007): 161–85. http://dx.doi.org/10.1002/qj.4970073902.

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23

Zöger, M., A. Afchine, N. Eicke, M. T. Gerhards, E. Klein, D. S. McKenna, U. Mörschel, et al. "Fast in situ stratospheric hygrometers: A new family of balloon-borne and airborne Lyman α photofragment fluorescence hygrometers." Journal of Geophysical Research: Atmospheres 104, no. D1 (January 1, 1999): 1807–16. http://dx.doi.org/10.1029/1998jd100025.

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Beaton, Stuart P., and Mike Spowart. "UV Absorption Hygrometer for Fast-Response Airborne Water Vapor Measurements." Journal of Atmospheric and Oceanic Technology 29, no. 9 (September 1, 2012): 1295–303. http://dx.doi.org/10.1175/jtech-d-11-00141.1.

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Abstract A next-generation vacuum-ultraviolet (Lyman-alpha) absorption hygrometer for high-rate research aircraft humidity measurements designed by the National Center for Atmospheric Research is described. It retains the high data rate, optical and mechanical simplicity, and low maintenance of previous Lyman-alpha hygrometers, while incorporating modern electronics and rugged, long-lived commercially available lamps and detectors. The mass of the sensing head is 2.0 kg in a volume of 3700 cm3, while the power supply is 1.3 kg mass in a volume of 1100 cm3. Power draw is 0.2 A at 120 V alternating current (AC). In bench and aircraft flight testing the prototype shows a bandwidth of 35 Hz and mixing ratio noise of ±0.5% over a water vapor mixing ratio range of 2–15 g kg−1. This range can be scaled to lower mixing ratios by increasing the pathlength. This performance enables measurements of water vapor concentration with high spatial resolution from research aircraft. The prototype instrument has flown over 380 h with minimal maintenance or repairs.

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Milosevic, Nenad, Nenad Stepanic, and Marijana Babic. "A relative humidity calibration from 5°C to 45°C in a mixed-flow humidity generator." Thermal Science 16, no. 1 (2012): 193–205. http://dx.doi.org/10.2298/tsci1201193m.

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The paper presents a method used in the Vinca Institute of Nuclear Sciences for a reliable and traceable relative humidity calibration in the temperature range from 5?C to 45?C. Inside a controllable temperature and humidity environment, supplied by a mixed-flow humidity generator, measurements of hygrometers under calibration are compared with those of calibrated reference instruments. A traceability chain from temperature to reference relative humidity and next to the hygrometers under calibrations is provided by using a chilled-mirror dew-point temperature system and precise relative humidity probes. Corresponding calibration uncertainties are analyzed, particularly those associated to the temperature uniformity of controlled calibration environment. Two examples of relative humidity calibration with dew-point and relative humidity reference measurements in the range from 15 to 75% of RH and 5?C to 45?C are presented and discussed.

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Lang, Benjamin, Wolfgang Breitfuss, Simon Schweighart, Philipp Breitegger, Hugo Pervier, Andreas Tramposch, Andreas Klug, Wolfgang Hassler, and Alexander Bergmann. "Photoacoustic hygrometer for icing wind tunnel water content measurement: design, analysis, and intercomparison." Atmospheric Measurement Techniques 14, no. 3 (March 31, 2021): 2477–500. http://dx.doi.org/10.5194/amt-14-2477-2021.

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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.

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Hurst, D. F., E. G. Hall, A. F. Jordan, L. M. Miloshevich, D. N. Whiteman, T. Leblanc, D. Walsh, H. Vömel, and S. J. Oltmans. "Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE-2009." Atmospheric Measurement Techniques 4, no. 12 (December 16, 2011): 2777–93. http://dx.doi.org/10.5194/amt-4-2777-2011.

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Abstract. We compare coincident, in situ, balloon-borne measurements of temperature (T) and pressure (P) by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and similar measurements of relative humidity (RH) by RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with at least one pair of radiosondes are analyzed in 1-km altitude bins to quantify measurement differences between the sonde sensors and how they vary with altitude. Each comparison (T, P, RH) exposes several profiles of anomalously large measurement differences. Measurement difference statistics, calculated with and without the anomalous profiles, are compared to uncertainties quoted by the radiosonde manufacturers. Excluding seven anomalous profiles, T differences between 19 pairs of RS92 and iMet sondes exceed their measurement uncertainty limits (2 σ) 31% of the time and reveal a statistically significant, altitude-independent bias of 0.5 ± 0.2 °C. Similarly, RS92-iMet P differences in 22 non-anomalous profiles exceed their uncertainty limits 23% of the time, with a disproportionate 83% of the excessive P differences at altitudes >16 km. The RS92-iMet pressure differences increase smoothly from −0.6 hPa near the surface to 0.8 hPa above 25 km. Temperature and P differences between all 14 pairs of RS92 sondes exceed manufacturer-quoted, reproducibility limits (σ) 28% and 11% of the time, respectively. About 95% of the excessive T differences are eliminated when 5 anomalous RS92-RS92 profiles are excluded. Only 5% of RH measurement differences between 14 pairs of RS92 sondes exceed the manufacturer's measurement reproducibility limit (σ). RH measurements by RS92 sondes are also compared to RH values calculated from frost point hygrometer measurements and coincident T measurements by the radiosondes. The influences of RS92-iMet Tand P differences on RH values and water vapor mixing ratios calculated from frost point hygrometer measurements are examined.

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Leone, Marco, Sofia Principe, Marco Consales, Roberto Parente, Armando Laudati, Stefano Caliro, Antonello Cutolo, and Andrea Cusano. "Fiber Optic Thermo-Hygrometers for Soil Moisture Monitoring." Sensors 17, no. 6 (June 20, 2017): 1451. http://dx.doi.org/10.3390/s17061451.

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29

Afchine, Armin, Christian Rolf, Anja Costa, Nicole Spelten, Martin Riese, Bernhard Buchholz, Volker Ebert, et al. "Ice particle sampling from aircraft – influence of the probing position on the ice water content." Atmospheric Measurement Techniques 11, no. 7 (July 11, 2018): 4015–31. http://dx.doi.org/10.5194/amt-11-4015-2018.

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Abstract. The ice water content (IWC) of cirrus clouds is an essential parameter determining their radiative properties and thus is important for climate simulations. Therefore, for a reliable measurement of IWC on board research aircraft, it is important to carefully design the ice crystal sampling and measuring devices. During the ML-CIRRUS field campaign in 2014 with the German Gulfstream GV HALO (High Altitude and Long Range Research Aircraft), IWC was recorded by three closed-path total water together with one gas-phase water instrument. The hygrometers were supplied by inlets mounted on the roof of the aircraft fuselage. Simultaneously, the IWC is determined by a cloud particle spectrometer attached under an aircraft wing. Two more examples of simultaneous IWC measurements by hygrometers and cloud spectrometers are presented, but the inlets of the hygrometers were mounted at the fuselage side (M-55 Geophysica, StratoClim campaign 2017) and bottom (NASA WB57, MacPex campaign 2011). This combination of instruments and inlet positions provides the opportunity to experimentally study the influence of the ice particle sampling position on the IWC with the approach of comparative measurements. As expected from theory and shown by computational fluid dynamics (CFD) calculations, we found that the IWCs provided by the roof inlets deviate from those measured under the aircraft wing. As a result of the inlet position in the shadow zone behind the aircraft cockpit, ice particle populations with mean mass sizes larger than about 25 µm radius are subject to losses, which lead to strongly underestimated IWCs. On the other hand, cloud populations with mean mass sizes smaller than about 12 µm are dominated by particle enrichment and thus overestimated IWCs. In the range of mean mass sizes between 12 and 25 µm, both enrichment and losses of ice crystals can occur, depending on whether the ice crystal mass peak of the size distribution – in these cases bimodal – is on the smaller or larger mass mode. The resulting deviations of the IWC reach factors of up to 10 or even more for losses as well as for enrichment. Since the mean mass size of ice crystals increases with temperature, losses are more pronounced at higher temperatures, while at lower temperatures IWC is more affected by enrichment. In contrast, in the cases where the hygrometer inlets were mounted at the fuselage side or bottom, the agreement of IWCs is most frequently within a factor of 2.5 or better – due to less disturbed ice particle sampling, as expected from theory – independently of the mean ice crystal sizes. The rather large scatter between IWC measurements reflects, for example, cirrus cloud inhomogeneities and instrument uncertainties as well as slight sampling biases which might also occur on the side or bottom of the fuselage and under the wing. However, this scatter is in the range of other studies and represent the current best possible IWC recording on fast-flying aircraft.

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Khaykin, S. M., I. Engel, H. Vömel, I. M. Formanyuk, R. Kivi, L. I. Korshunov, M. Krämer, et al. "Arctic stratospheric dehydration – Part 1: Unprecedented observation of vertical redistribution of water." Atmospheric Chemistry and Physics 13, no. 22 (November 27, 2013): 11503–17. http://dx.doi.org/10.5194/acp-13-11503-2013.

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Abstract. We present high-resolution measurements of water vapour, aerosols and clouds in the Arctic stratosphere in January and February 2010 carried out by in situ instrumentation on balloon sondes and high-altitude aircraft combined with satellite observations. The measurements provide unparalleled evidence of dehydration and rehydration due to gravitational settling of ice particles. An extreme cooling of the Arctic stratospheric vortex during the second half of January 2010 resulted in a rare synoptic-scale outbreak of ice polar stratospheric clouds (PSCs) remotely detected by the lidar aboard the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) satellite. The widespread occurrence of ice clouds was followed by sedimentation and consequent sublimation of ice particles, leading to vertical redistribution of water inside the vortex. A sequence of balloon and aircraft soundings with chilled mirror and Lyman- α hygrometers (Cryogenic Frostpoint Hygrometer, CFH; Fast In Situ Stratospheric Hygrometer, FISH; Fluorescent Airborne Stratospheric Hygrometer, FLASH) and backscatter sondes (Compact Optical Backscatter Aerosol Detector, COBALD) conducted in January 2010 within the LAPBIAT (Lapland Atmosphere-Biosphere Facility) and RECONCILE (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) campaigns captured various phases of this phenomenon: ice formation, irreversible dehydration and rehydration. Consistent observations of water vapour by these independent measurement techniques show clear signatures of irreversible dehydration of the vortex air by up to 1.6 ppmv in the 20–24 km altitude range and rehydration by up to 0.9 ppmv in a 1 km thick layer below. Comparison with space-borne Aura MLS (Microwave Limb Sounder) water vapour observations allow the spatiotemporal evolution of dehydrated air masses within the Arctic vortex to be derived and upscaled.

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Suortti, T. M., R. Kivi, A. Kats, V. Yushkov, N. Kämpfer, U. Leiterer, L. M. Miloshevich, et al. "Tropospheric Comparisons of Vaisala Radiosondes and Balloon-Borne Frost-Point and Lyman-α Hygrometers during the LAUTLOS-WAVVAP Experiment." Journal of Atmospheric and Oceanic Technology 25, no. 2 (February 1, 2008): 149–66. http://dx.doi.org/10.1175/2007jtecha887.1.

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Abstract The accuracy of all types of Vaisala radiosondes and two types of Snow White chilled-mirror hygrosondes was assessed in an intensive in situ comparison with reference hygrometers. Fourteen nighttime reference comparisons were performed to determine a working reference for the radiosonde comparisons. These showed that the night version of the Snow White agreed best with the references [i.e., the NOAA frost-point hygrometer (FPH) and University of Colorado cryogenic frost-point hygrometer (CFH)], but that the daytime version had severe problems with contamination in the humid upper troposphere. Since the RS92 performance was superior to the other radiosondes and to the day version of the Snow White, it was selected to be the working reference. According to the reference comparison, the RS92 has no bias in the mid- and lower troposphere, with deviations <±5% in relative humidity (RH). In the upper troposphere, the RS92 has a ∼5% RH wet bias, which is partly due to the RS92 time lag error and the termination of the heating cycle. It was shown that the time lag effects relating to Vaisala radiosondes can be corrected. Because these were nighttime comparisons, they can be considered to be free from solar radiation effects. Neither the radiosondes nor the Snow White succeeded in reproducing reference class hygrometer profiles in the stratosphere. According to the 29 radiosonde intercomparisons, the RS92 and the modified RS90 (FN) had the best mutual agreement and no bias. The disagreement is largest (<±10% RH) at low temperatures (T ≪ −30°C), where the FN underestimated (overestimated) in high (low) ambient RH. In comparison with the RS92, the RS90 had a semilinearly increasing wet bias with decreasing temperature, where the bias was ∼10% RH at −60°C. The RS80-A suffers from a large temperature-dependent dry bias in high RH conditions, being over 30% RH at −60°C and ∼5% RH near 0°C. The RS80-A dry bias can be almost totally removed with the correction algorithm by Leiterer et al., which was chosen as the best available. The other approach tested tends to overcorrect in high RH conditions when T < −50°C. For T > −30°C it is ineffective and does not correct the RS80-A dry bias in high ambient RH.

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32

Singer, Clare E., Benjamin W. Clouser, Sergey M. Khaykin, Martina Krämer, Francesco Cairo, Thomas Peter, Alexey Lykov, et al. "Intercomparison of upper tropospheric and lower stratospheric water vapor measurements over the Asian Summer Monsoon during the StratoClim campaign." Atmospheric Measurement Techniques 15, no. 16 (August 23, 2022): 4767–83. http://dx.doi.org/10.5194/amt-15-4767-2022.

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Abstract. In situ measurements in the climatically important upper troposphere–lower stratosphere (UTLS) are critical for understanding controls on cloud formation, the entry of water into the stratosphere, and hydration–dehydration of the tropical tropopause layer. Accurate in situ measurement of water vapor in the UTLS however is difficult because of low water vapor concentrations (<5 ppmv) and a challenging low temperature–pressure environment. The StratoClim campaign out of Kathmandu, Nepal, in July and August 2017, which made the first high-altitude aircraft measurements in the Asian Summer Monsoon (ASM), also provided an opportunity to intercompare three in situ hygrometers mounted on the M-55 Geophysica: ChiWIS (Chicago Water Isotope Spectrometer), FISH (Fast In situ Stratospheric Hygrometer), and FLASH (Fluorescent Lyman-α Stratospheric Hygrometer). Instrument agreement was very good, suggesting no intrinsic technique-dependent biases: ChiWIS measures by mid-infrared laser absorption spectroscopy and FISH and FLASH by Lyman-α induced fluorescence. In clear-sky UTLS conditions (H2O<10 ppmv), mean and standard deviations of differences in paired observations between ChiWIS and FLASH were only (-1.4±5.9) % and those between FISH and FLASH only (-1.5±8.0) %. Agreement between ChiWIS and FLASH for in-cloud conditions is even tighter, at (+0.7±7.6) %. Estimated realized instrumental precision in UTLS conditions was 0.05, 0.2, and 0.1 ppmv for ChiWIS, FLASH, and FISH, respectively. This level of accuracy and precision allows the confident detection of fine-scale spatial structures in UTLS water vapor required for understanding the role of convection and the ASM in the stratospheric water vapor budget.

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Hasebe, F., M. Fujiwara, N. Nishi, M. Shiotani, H. Vömel, S. Oltmans, H. Takashima, S. Saraspriya, N. Komala, and Y. Inai. "In situ observations of dehydrated air parcels advected horizontally in the Tropical Tropopause Layer of the western Pacific." Atmospheric Chemistry and Physics 7, no. 3 (February 14, 2007): 803–13. http://dx.doi.org/10.5194/acp-7-803-2007.

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Abstract. Water vapor observations by chilled-mirror hygrometers were conducted at Bandung, Indonesia (6.90° S, 107.60° E) and Tarawa, Kiribati (1.35° N, 172.91° E) in December 2003 to examine the efficiency of dehydration during horizontal advection in the tropical tropopause layer (TTL). Trajectory analyses based on bundles of isentropic trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels follow, for interpreting the water vapor concentrations observed by chilled-mirror frostpoint hygrometers in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that drier air parcels were exposed to lower temperatures than were more humid ones during advection. Although the number of observations is quite limited, the water content in the observed air parcels on many occasions was more than that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observations.

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34

Pirog, V. P., A. M. Gaba, I. A. Rudykh, and A. K. Semchevskii. "Application of coulometric electrolytic cells in absolute humidity hygrometers." Measurement Techniques 53, no. 12 (March 2011): 1411–16. http://dx.doi.org/10.1007/s11018-011-9674-3.

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35

Stroikovskii, A. K., V. A. Pronyakin, and V. P. Dombrovskii. "Primary-converter parameters for neutron-scattering powder-material hygrometers." Measurement Techniques 33, no. 2 (February 1990): 180–83. http://dx.doi.org/10.1007/bf00866282.

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36

Khaykin, Sergey M., Jean-Pierre Pommereau, Emmanuel D. Riviere, Gerhard Held, Felix Ploeger, Melanie Ghysels, Nadir Amarouche, Jean-Paul Vernier, Frank G. Wienhold, and Dmitry Ionov. "Evidence of horizontal and vertical transport of water in the Southern Hemisphere tropical tropopause layer (TTL) from high-resolution balloon observations." Atmospheric Chemistry and Physics 16, no. 18 (September 29, 2016): 12273–86. http://dx.doi.org/10.5194/acp-16-12273-2016.

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Abstract. High-resolution in situ balloon measurements of water vapour, aerosol, methane and temperature in the upper tropical tropopause layer (TTL) and lower stratosphere are used to evaluate the processes affecting the stratospheric water budget: horizontal transport (in-mixing) and hydration by cross-tropopause overshooting updrafts. The obtained in situ evidence of these phenomena are analysed using satellite observations by Aura MLS (Microwave Limb Sounder) and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) together with trajectory and transport modelling performed using CLaMS (Chemical Lagrangian Model of the Stratosphere) and HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model. Balloon soundings were conducted during March 2012 in Bauru, Brazil (22.3° S) in the frame of the TRO-Pico campaign for studying the impact of convective overshooting on the stratospheric water budget. The balloon payloads included two stratospheric hygrometers: FLASH-B (Fluorescence Lyman-Alpha Stratospheric Hygrometer for Balloon) and Pico-SDLA instrument as well as COBALD (Compact Optical Backscatter Aerosol Detector) sondes, complemented by Vaisala RS92 radiosondes. Water vapour vertical profiles obtained independently by the two stratospheric hygrometers are in excellent agreement, ensuring credibility of the vertical structures observed. A signature of in-mixing is inferred from a series of vertical profiles, showing coincident enhancements in water vapour (of up to 0.5 ppmv) and aerosol at the 425 K (18.5 km) level. Trajectory analysis unambiguously links these features to intrusions from the Southern Hemisphere extratropical stratosphere, containing more water and aerosol, as demonstrated by MLS and CALIPSO global observations. The in-mixing is successfully reproduced by CLaMS simulations, showing a relatively moist filament extending to 20° S. A signature of local cross-tropopause transport of water is observed in a particular sounding, performed on a convective day and revealing water vapour enhancements of up to 0.6 ppmv as high as the 404 K (17.8 km) level. These are shown to originate from convective overshoots upwind detected by an S-band weather radar operating locally in Bauru. The accurate in situ observations uncover two independent moisture pathways into the tropical lower stratosphere, which are hardly detectable by space-borne sounders. We argue that the moistening by horizontal transport is limited by the weak meridional gradients of water, whereas the fast convective cross-tropopause transport, largely missed by global models, can have a substantial effect, at least at a regional scale.

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37

Eloranta, Edwin W., Roland B. Stull, and Elizabeth E. Ebert. "Test of a Calibration Device for Airborne Lyman-α Hygrometers." Journal of Atmospheric and Oceanic Technology 6, no. 1 (February 1989): 129–39. http://dx.doi.org/10.1175/1520-0426(1989)006<0129:toacdf>2.0.co;2.

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38

S. Irmak, D. Z. Haman, and A. Irmak. "Dew Point Hygrometers for Irrigation Scheduling in Fine-Textured Soils." Applied Engineering in Agriculture 17, no. 1 (2001): 17–25. http://dx.doi.org/10.13031/2013.1932.

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Sokov, I. A. "Estimate of incompleteness error of moisture absorption in coulometric hygrometers." Measurement Techniques 52, no. 12 (December 2009): 1365–71. http://dx.doi.org/10.1007/s11018-010-9446-5.

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40

E. M. Barber and D. Gu. "Performance of an Aspirated Psychrometer and Three Hygrometers in Livestock Barns." Applied Engineering in Agriculture 5, no. 4 (1989): 595–600. http://dx.doi.org/10.13031/2013.26567.

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41

Løkken, T. V. "Comparison of hygrometers for monitoring of water vapour in natural gas." Journal of Natural Gas Science and Engineering 6 (May 2012): 24–36. http://dx.doi.org/10.1016/j.jngse.2012.02.001.

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42

Hurst, D. F., E. G. Hall, A. F. Jordan, L. M. Miloshevich, D. N. Whiteman, T. Leblanc, D. Walsh, H. Vömel, and S. J. Oltmans. "Comparisons of temperature, pressure and humidity measurements by balloon-borne radiosondes and frost point hygrometers during MOHAVE 2009." Atmospheric Measurement Techniques Discussions 4, no. 4 (July 11, 2011): 4357–401. http://dx.doi.org/10.5194/amtd-4-4357-2011.

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Abstract. We compare coincident, balloon-borne, in situ measurements of temperature and pressure by two radiosondes (Vaisala RS92, Intermet iMet-1-RSB) and measurements of relative humidity (RH) by Vaisala RS92 sondes and frost point hygrometers. Data from a total of 28 balloon flights with mixed payloads are analyzed in 1-km altitude bins to quantify measurement biases between sensors and how they vary with altitude. The disparities between sensors determined here are compared to measurement uncertainties quoted by the two radiosonde manufacturers. Our comparisons expose several flight profiles with anomalously large measurement differences. Excluding these anomalous profiles, 33 % of RS92-iMet median temperature differences exceed the uncertainty limits calculated from manufacturer-quoted uncertainties. A statistically significant, altitude-independent bias of about 0.5 ± 0.2 °C is revealed for the RS92-iMet temperature differences. Similarly, 23 % of RS92-iMet median pressure differences exceed the quoted uncertainty limits, with 83 % of these excessive differences above 16 km altitude. The pressure differences are altitude dependent, increasing from −0.6 ± 0.9 hPa at the surface to 0.7 ± 0.1 hPa above 15 km. Temperature and pressure differences between redundant RS92 sondes on the same balloon exceed manufacturer-quoted reproducibility limits 20 % and 2 % of the time, respectively, with most of the excessive differences belonging to anomalous difference profiles. Relative humidity measurements by RS92 sondes are compared to other RS92 sondes and to RH values calculated using frost point hygrometer measurements and coincident radiosonde temperature measurements. For some flights the RH differences are anomalously large, but in general are within the ±5 % RH measurement uncertainty limits quoted for the RS92. The quantitative effects of RS92 and iMet pressure and temperature differences on frost point-based water vapor mixing ratios and RH values, respectively, are also presented.

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43

Leblanc, T., T. D. Walsh, I. S. McDermid, G. C. Toon, J. F. Blavier, B. Haines, W. G. Read, et al. "Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE)-2009: overview of campaign operations and results." Atmospheric Measurement Techniques Discussions 4, no. 3 (May 31, 2011): 3277–336. http://dx.doi.org/10.5194/amtd-4-3277-2011.

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Abstract. The Measurements of Humidity in the Atmosphere and Validation Experiment (MOHAVE) 2009 campaign took place on 11–27 October 2009 at the JPL Table Mountain Facility in California (TMF). The main objectives of the campaign were to (1) validate the water vapor measurements of several instruments, including, three Raman lidars, two microwave radiometers, two Fourier-Transform spectrometers, and two GPS receivers (column water), (2) cover water vapor measurements from the ground to the mesopause without gaps, and (3) study upper tropospheric humidity variability at timescales varying from a few minutes to several days. A total of 58 radiosondes and 20 Frost-Point hygrometer sondes were launched. Two types of radiosondes were used during the campaign. Non negligible differences in the readings between the two radiosonde types used (Vaisala RS92 and InterMet iMet-1) made a small, but measurable impact on the derivation of water vapor mixing ratio by the Frost-Point hygrometers. As observed in previous campaigns, the RS92 humidity measurements remained within 5 % of the Frost-point in the lower and mid-troposphere, but were too dry in the upper troposphere. Over 270 h of water vapor measurements from three Raman lidars (JPL and GSFC) were compared to RS92, CFH, and NOAA-FPH. The JPL lidar profiles reached 20 km when integrated all night, and 15 km when integrated for 1 h. Excellent agreement between this lidar and the frost-point hygrometers was found throughout the measurement range, with only a 3 % (0.3 ppmv) mean wet bias for the lidar in the upper troposphere and lower stratosphere (UTLS). The other two lidars provided satisfactory results in the lower and mid-troposphere (2–5 % wet bias over the range 3–10 km), but suffered from contamination by fluorescence (wet bias ranging from 5 to 50 % between 10 km and 15 km), preventing their use as an independent measurement in the UTLS. The comparison between all available stratospheric sounders allowed to identify only the largest biases, in particular a 10 % dry bias of the Water Vapor Millimeter-wave Spectrometer compared to the Aura-Microwave Limb Sounder. No other large, or at least statistically significant, biases could be observed. Total Precipitable Water (TPW) measurements from six different co-located instruments were available. Several retrieval groups provided their own TPW retrievals, resulting in the comparison of 10 different datasets. Agreement within 7 % (0.7 mm) was found between all datasets. Such good agreement illustrates the maturity of these measurements and raises confidence levels for their use as an alternate or complementary source of calibration for the Raman lidars. Tropospheric and stratospheric ozone and temperature measurements were also available during the campaign. The water vapor and ozone lidar measurements, together with the advected potential vorticity results from the high-resolution transport model MIMOSA, allowed the identification and study of a deep stratospheric intrusion over TMF. These observations demonstrated the lidar strong potential for future long-term monitoring of water vapor in the UTLS.

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44

Leblanc, T., T. D. Walsh, I. S. McDermid, G. C. Toon, J. F. Blavier, B. Haines, W. G. Read, et al. "Measurements of Humidity in the Atmosphere and Validation Experiments (MOHAVE)-2009: overview of campaign operations and results." Atmospheric Measurement Techniques 4, no. 12 (December 1, 2011): 2579–605. http://dx.doi.org/10.5194/amt-4-2579-2011.

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Abstract. The Measurements of Humidity in the Atmosphere and Validation Experiment (MOHAVE) 2009 campaign took place on 11–27 October 2009 at the JPL Table Mountain Facility in California (TMF). The main objectives of the campaign were to (1) validate the water vapor measurements of several instruments, including, three Raman lidars, two microwave radiometers, two Fourier-Transform spectrometers, and two GPS receivers (column water), (2) cover water vapor measurements from the ground to the mesopause without gaps, and (3) study upper tropospheric humidity variability at timescales varying from a few minutes to several days. A total of 58 radiosondes and 20 Frost-Point hygrometer sondes were launched. Two types of radiosondes were used during the campaign. Non negligible differences in the readings between the two radiosonde types used (Vaisala RS92 and InterMet iMet-1) made a small, but measurable impact on the derivation of water vapor mixing ratio by the Frost-Point hygrometers. As observed in previous campaigns, the RS92 humidity measurements remained within 5% of the Frost-point in the lower and mid-troposphere, but were too dry in the upper troposphere. Over 270 h of water vapor measurements from three Raman lidars (JPL and GSFC) were compared to RS92, CFH, and NOAA-FPH. The JPL lidar profiles reached 20 km when integrated all night, and 15 km when integrated for 1 h. Excellent agreement between this lidar and the frost-point hygrometers was found throughout the measurement range, with only a 3% (0.3 ppmv) mean wet bias for the lidar in the upper troposphere and lower stratosphere (UTLS). The other two lidars provided satisfactory results in the lower and mid-troposphere (2–5% wet bias over the range 3–10 km), but suffered from contamination by fluorescence (wet bias ranging from 5 to 50% between 10 km and 15 km), preventing their use as an independent measurement in the UTLS. The comparison between all available stratospheric sounders allowed to identify only the largest biases, in particular a 10% dry bias of the Water Vapor Millimeter-wave Spectrometer compared to the Aura-Microwave Limb Sounder. No other large, or at least statistically significant, biases could be observed. Total Precipitable Water (TPW) measurements from six different co-located instruments were available. Several retrieval groups provided their own TPW retrievals, resulting in the comparison of 10 different datasets. Agreement within 7% (0.7 mm) was found between all datasets. Such good agreement illustrates the maturity of these measurements and raises confidence levels for their use as an alternate or complementary source of calibration for the Raman lidars. Tropospheric and stratospheric ozone and temperature measurements were also available during the campaign. The water vapor and ozone lidar measurements, together with the advected potential vorticity results from the high-resolution transport model MIMOSA, allowed the identification and study of a deep stratospheric intrusion over TMF. These observations demonstrated the lidar strong potential for future long-term monitoring of water vapor in the UTLS.

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45

Kim, Jong Chul, Byung Il Choi, Sang-Bong Woo, Yong-Gyoo Kim, and Sang-Wook Lee. "The Effect of Temperature on Aluminum Oxide and Chilled Mirror Dew-point Hygrometers." Journal of Sensor Science and Technology 26, no. 1 (January 31, 2017): 50–55. http://dx.doi.org/10.5369/jsst.2017.26.1.50.

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46

Neis, Patrick, Herman G. J. Smit, Susanne Rohs, Ulrich Bundke, Martina Krämer, Nicole Spelten, Volker Ebert, Bernhard Buchholz, Karin Thomas, and Andreas Petzold. "Quality assessment of MOZAIC and IAGOS capacitive hygrometers: insights from airborne field studies." Tellus B: Chemical and Physical Meteorology 67, no. 1 (October 22, 2015): 28320. http://dx.doi.org/10.3402/tellusb.v67.28320.

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47

Benyon, R., T. Vicente, P. Hernández, L. De Rivas, and F. Conde. "Evaluation of the Long-Term Stability and Temperature Coefficient of Dew-Point Hygrometers." International Journal of Thermophysics 33, no. 8-9 (September 2012): 1758–70. http://dx.doi.org/10.1007/s10765-012-1346-2.

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48

Sakai, Tetsu, Tomohiro Nagai, Masahisa Nakazato, Takatsugu Matsumura, Narihiro Orikasa, and Yoshinori Shoji. "Comparisons of Raman Lidar Measurements of Tropospheric Water Vapor Profiles with Radiosondes, Hygrometers on the Meteorological Observation Tower, and GPS at Tsukuba, Japan." Journal of Atmospheric and Oceanic Technology 24, no. 8 (August 1, 2007): 1407–23. http://dx.doi.org/10.1175/jtech2056.1.

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Abstract The vertical distribution profiles of the water vapor mixing ratio (w) were measured by Raman lidar at the Meteorological Research Institute, Japan, during the period from 2000 to 2004. The measured values were compared with those obtained with radiosondes, hygrometers on a meteorological observation tower, and global positioning system (GPS) antennas near the lidar site. The values of w obtained with the lidar were lower than those obtained with the corrected Meisei RS2-91 radiosonde by 1.2% on average and higher than those obtained with the corrected Vaisala RS80-A radiosonde by 17% for w ≥ 0.5 g kg−1. The lidar data were higher than those radiosondes’ data by 19% or 33% for w < 0.5 g kg−1. The vertical variations of w obtained with the lidar differed from those obtained with the Meisei RS-01G radiosonde and Meteolabor Snow White radiosonde by 5% on average for w ≥ 0.5 g kg−1. The lidar data were lower than those radiosondes’ data by 37% or 39% for w < 0.5 g kg−1. The temporal variations of w obtained with the lidar and the hygrometers on the meteorological tower agreed to within 0.4% at a height of 213 m, although the absolute values differed systematically by 9%–14% due to the incomplete overlap of the laser beam and the receiver’s field of view at heights between 50 and 150 m. The precipitable water vapor obtained with the lidar indicated a mean positive bias of 2 mm (9%–11%) relative to those obtained with GPS. The lidar water vapor calibration coefficient that was calculated using RS2-91 radiosonde data varied by 11% during an 18-month period. Therefore, it is necessary to develop an accurate, yet convenient, method for determining the calibration coefficient for the use of the lidar.

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49

Müller, M., R. Neuber, F. Fierli, A. Hauchecorne, H. Vömel, and S. J. Oltmans. "Stratospheric water vapour as tracer for Vortex filamentation in the Arctic winter 2002/2003." Atmospheric Chemistry and Physics 3, no. 6 (November 13, 2003): 1991–97. http://dx.doi.org/10.5194/acp-3-1991-2003.

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Abstract. Balloon-borne frost point hygrometers measured three high-resolution profiles of stratospheric water vapour above Ny-Ålesund, Spitsbergen during winter 2002/2003. The profiles obtained on 12 December 2002 and on 17 January 2003 provide an insight into the vertical distribution of water vapour in the core of the polar vortex. The water vapour sounding on 11 February 2003 was obtained within the vortex edge region of the lower stratosphere. Here, a significant reduction of water vapour mixing ratio was observed between 16 and 19 km. The stratospheric temperatures indicate that this dehydration was not caused by the presence of polar stratospheric clouds or earlier PSC particle sedimentation. Ozone observations on this day indicate a large scale movement of the polar vortex and show laminae in the same altitude range as the water vapour profile. The link between the observed water vapour reduction and filaments in the vortex edge region is indicated in the results of the semi-lagrangian advection model MIMOSA, which show that adjacent filaments of polar and mid latitude air can be identified above the Spitsbergen region. A vertical cross-section produced by the MIMOSA model reveals that the water vapour sonde flew through polar air in the lowest part of the stratosphere below 425 K, then passed through filaments of mid latitude air with lower water vapour concentrations, before it finally entered the polar vortex above 450 K. These results indicate that on 11 February 2003 the frost point hygrometer measured different water vapour concentrations as the sonde detected air with different origins. Instead of being linked to dehydration due to PSC particle sedimentation, the local reduction in the stratospheric water vapour profile was in this case caused by dynamical processes in the polar stratosphere.

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Kursinski, E. R., D. Ward, M. Stovern, A. C. Otarola, A. Young, B. Wheelwright, R. Stickney, et al. "Development and testing of the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS) cm and mm wavelength occultation instrument." Atmospheric Measurement Techniques 5, no. 2 (February 27, 2012): 439–56. http://dx.doi.org/10.5194/amt-5-439-2012.

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Abstract. We present initial results from testing a new remote sensing system called the Active Temperature, Ozone and Moisture Microwave Spectrometer (ATOMMS). ATOMMS is designed as a satellite-to-satellite occultation system for monitoring climate. We are developing the prototype instrument for an aircraft to aircraft occultation demonstration. Here we focus on field testing of the ATOMMS instrument, in particular the remote sensing of water by measuring the attenuation caused by the 22 GHz and 183 GHz water absorption lines. Our measurements of the 183 GHz line spectrum along an 820 m path revealed that the AM 6.2 spectroscopic model provdes a much better match to the observed spectrum than the MPM93 model. These comparisons also indicate that errors in the ATOMMS amplitude measurements are about 0.3%. Pressure sensitivity bodes well for ATOMMS as a climate instrument. Comparisons with a hygrometer revealed consistency at the 0.05 mb level, which is about 1% of the absolute humidity. Initial measurements of absorption by the 22 GHz line made along a 5.4 km path between two mountaintops captured a large increase in water vapor similar to that measured by several nearby hygrometers. A storm passage between the two instruments yielded our first measurements of extinction by rain and cloud droplets. Comparisons of ATOMMS 1.5 mm opacity measurements with measured visible opacity and backscatter from a weather radar revealed features simultaneously evident in all three datasets confirming the ATOMMS measurements. The combined ATOMMS, radar and visible information revealed the evolution of rain and cloud amounts along the signal path during the passage of the storm. The derived average cloud water content reached typical continental cloud amounts. These results demonstrated a significant portion of the information content of ATOMMS and its ability to penetrate through clouds and rain which is critical to its all-weather, climate monitoring capability.

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Journal articles on the topic 'Hygrometers'

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