Boundary-Layer Meteorology

, Volume 74, Issue 4, pp 353–370 | Cite as

A fast response, open path, infrared hygrometer, using a semiconductor source

  • A. E. Green
  • W. Kohsiek


Investigations were carried out as to the feasibility of using a semiconductor source in the design of a new rapid response, open-path hygrometer. A single-beam instrument was constructed employing an infrared light emitting diode (LED) as a source instead of the usual high energy, wideband filament. The spectral emission envelope encompassed the 1.87 μm water absorption band. Electronic modulation and thermoelectrical cooling of the diode eliminated the conventional chopper wheel and stabilized the peak wavelength emission. Path length was 200 mm. Over a water vapour concentration range of 0–16 g m−3, absorption varied by 2% in a linear fashion. At 10 Hz, the noise level was 0.1 g m−3 rms. Hygrometer resolution and stability are constrained by the detector noise level, the small source emission in the absorption band and low frequency drift in the optical filter. Despite these problems, the new instrument showed comparable performance characteristics to a commercial Lyman-α hygrometer. Latent heat fluxes measured with both instruments and a Kaijo-Denki, 3-D sonic anemometer agreed to within 4% over a range 0–350 W m−2. Further improvements in performance can be anticipated with advances in detector and LED technology.


Light Emit Diode Latent Heat Flux Sonic Anemometer Water Vapour Concentration Frequency Drift 
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  1. Auble, D. L. and Meyers, T. P.: 1992, ‘An Open Path, Fast Response Infrared Absorption Gas Analyser for H2O and CO2’,Boundary-Layer Meteorol. 59, 243–256.Google Scholar
  2. Brooks, D. L.: 1971, ‘Development of an Infrared Absorption Hygrometer using Solid State Energy Sources’, M.S. Thesis, Dept. Atmospheric Sciences, University of Washington, Seattle, Wa. 42 pp.Google Scholar
  3. Buck, A. L.: 1976, ‘The Variable-Path Lyman-Alpha Hygrometer and its Operating Characteristics’,Bull. Amer. Meteorol. Soc. 57, 1113–1118.Google Scholar
  4. Campbell, G. S. and Tanner, B. D.: 1985, ‘A Krypton Hygrometer for Measurement of Atmospheric Water Vapor Concentration’, Proceedings of the 1985 International Symposium on Moisture and Humidity, ISA, Research Triangle Park, Washington, DC, pp. 609–612.Google Scholar
  5. Chen, H. and Mitsuta, Y.: 1967, An Infrared Absorption Hygrometer and its Application to the Study of the Water Vapor Flux Near the Ground’, Special Contribution, Geophysical Institute, Kyoto University,7, 83–94.Google Scholar
  6. Fowle, F. E.: 1912, ‘The Spectroscopic Determination of Aqueous Vapor’,The Astrophysical Journal 35, 149–162.Google Scholar
  7. Heikinheimo, M. J., Thurtell, G. W. and Kidd, G. E.: 1989, ‘An Open Path, Fast Response IR Spectrometer for Simultaneous Detection of CO2 and Water Vapor Fluctuations’,J. Atmos. Oceanic Tech. 6, 624–636.Google Scholar
  8. Kohsiek, W.: 1991, ‘Infrared H2O/CO2 Sensor with Fiber Optics’, Presented at the Seventh AMS Symposium on Meteorological Observations and Instrumentation’, Jan. 13–18, New Orleans, LA.Google Scholar
  9. McBean, G. A.: 1972, ‘Instrument Requirements for Eddy-Correlation Measurements’J. Appl. Meteorol. 11, 1078–1084.Google Scholar
  10. Moore, C. J.: 1983, ‘On the Calibration and Temperature Behaviour of Single-Beam Infrared Hygrometers’,Boundury-Layer Meteorol. 25, 245–269.Google Scholar
  11. Ohatki, E. and Matsui, T.: 1982, ‘Infrared Device for Simultaneous Measurement of Fluctuations of Atmospheric Carbon Dioxide and Water Vapor’,Boundary-Layer Meteorol. 24, 109–119.Google Scholar
  12. Park, J. H.: 1977, ‘Atlas of Infrared Absorption Lines, NASA Contractor Report 2925’, Scientific and Technical Information Office, NASA.Google Scholar
  13. Schurer, K., Maandonks, R. and Visscher, G. J. W.: 1985, ‘Infrared Measurement of Water Vapour Fluctuations’, International Symposium Moisture and Humidity, Crystal City, VA., pp. 775–777.Google Scholar
  14. Tillman, J. E.: 1985, ‘Near Infrared Humidity Techniques using Semiconductor Sources; Incoherent Sources and Theoretical Calculations in the Presence of Cloud and Fog’,International Symposium Moisture and Humidity, Crystal City, VA., pp. 791–795.Google Scholar
  15. Trevitt, A. C. F.: 1986, ‘An Infrared Hygrometer with On-Line Temperature Compensation’,Boundary-Layer Meteorol. 34, 157–169.Google Scholar
  16. Raupach, M. R.: 1978, ‘Infrared Fluctuation Hygrometry in the Atmospheric Surface Layer’,Quart. J. R. Meteorol. Soc. 104, 309–322.Google Scholar
  17. Wolfe, W. L. and Zissis, G. J. (eds.): 1989,The Infrared Handbook, ‘Chapter 5, Atmospheric Absorption’.Google Scholar

Copyright information

© Kluwer Academic Publishers 1995

Authors and Affiliations

  • A. E. Green
    • 1
  • W. Kohsiek
    • 2
  1. 1.Kerikeri Research CentreThe Horticultural Research Institute of New ZealandKerikeri, Bay of IslandsNew Zealand
  2. 2.Royal Netherlands Meteorological Institute (KNMI)De BiltThe Netherlands

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