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4 - Humidity

Published online by Cambridge University Press:  05 July 2014

Ian Strangeways
Ian Strangeways
Affiliation:
TerraData
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Summary

One morning the view was singularly clear, the distant mountains being projected with the sharpest outline, on a heavy bank of dark blue clouds. Judging from the appearance, and from similar cases in England, I supposed the air was saturated with moisture. The fact, however, turned out quite the contrary. The hygrometer gave a difference of 29.6 degrees (F), between the temperature of the air, and the point at which dew was precipitated. This difference was nearly double that which I had observed on the previous mornings. This unusual degree of atmospheric dryness was accompanied by continual flashes of lightning. Is it not an uncommon case, thus to find a remarkable degree of aerial transparency with such a state of weather?

Charles Darwin Voyage of the Beagle (Cape de Verd Islands).

The variable

Just as air, warmed by contact with the ground, is transferred into the atmosphere by processes of diffusion, turbulence and convection, so too is the water vapour produced by evaporation. The ratio in which the net radiative energy is divided between heating the atmosphere, heating the ground and evaporating water is dependent on many factors, such as the amount of water actually available, the nature of the ground and the type of vegetation. Knowing the rate of evaporation of water is useful information in hydrology, meteorology and agriculture, but it is difficult to measure. However, the amount of water vapour in the air, i.e. the air’s humidity, is easier to measure and this chapter looks at how it is done; Chapter 7 addresses the more difficult problem of how evaporation rates are measured.

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Measuring the Natural Environment , pp. 53 - 68
Publisher: Cambridge University Press
Print publication year: 2003

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References

Bultot, F. & Dupriez, G. L. (1971) Comparaison d'instruments de mesure de l'humidité sous abri. Arch. Meteotol. Geophys. Bioklimatol, Wien, 19B, 53–6.CrossRefGoogle Scholar
Folland, C. K. (1975) The use of the lithium chloride hygrometer (dew-cell) to measure dew-point. Met. Mag., 104, 52–6.Google Scholar
Jason, A. C. (1965) Some properties and limitations of the aluminium oxide hygrometer. In Humidity and Moisture, Vol. 1, Principles and Methods of Measuring Humidity in Gases, ed. A., Wexler, pp. 372–90. Chapman & Hall.Google Scholar
Met. Office (1982a) The Handbook of Meteorological Instruments. HMSO, London.
Met. Office (1982b) The Observer's Handbook. HMSO, London.
Moore, C. J., McNeil, D. D. & Shuttleworth, W. J. (1976) A review of existing eddy-correlation sensors. Institute of Hydrology Report 32, pp. 22–3.Google Scholar
Musa, R. C. & Schnable, G. L. (1965) Polyelectrolyte electrical resistance humidity elements. In Humidity and Moisture, Vol. 1, Principles and Methods of Measuring Humidity in Gases, ed. A., Wexler, pp. 346–57. Chapman & Hall.Google Scholar
Nelson, D. E. & Amdur, E. J. (1965) A relative humidity sensor based on the capacity variations of a plastic film condenser. In Humidity and Moisture, Vol. 1, Principles and Methods of Measuring Humidity in Gases, ed. A., Wexler, pp. 597–601. Chapman & Hall.Google Scholar
Salasmaa, E. & Kostamo, P. (1974) New thin film humidity sensor. In Proc. 3rd Symp. on Meteorological Observations and Instrumentation, pp. 33–38. American Meteorological Society.Google Scholar
Spilhaus, A. F. (1935) The transient condition of the human hair hygrometer element. MIT, Cambridge MA, Meteorological Course, Professional Notes No. 8, Part 1.Google Scholar
Stormbom, L. (1995) Recent advances in capacitive humidity sensors. Vaisala News 137, 15–18.Google Scholar
Wexler, A. (1965) Dew-point hygrometry. In Humidity and Moisture, Vol. 1, Principles and Methods of Measuring Humidity in Gases, ed. A., Wexler, pp. 125–215. Chapman & Hall.Google Scholar
Wylie, R. G. (1968) Resumé of knowledge of the properties of the psychrometer. CSIRO, Melbourne, Report No. PIR-64.Google Scholar
Young, J. F. (1967) Humidity control in the laboratory using salt solutions – a review. J. Appl. Chem., 17, September 1967.Google Scholar

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  • Humidity
  • Ian Strangeways, TerraData
  • Book: Measuring the Natural Environment
  • Online publication: 05 July 2014
  • Chapter DOI: https://doi.org/10.1017/CBO9781139087254.004
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  • Humidity
  • Ian Strangeways, TerraData
  • Book: Measuring the Natural Environment
  • Online publication: 05 July 2014
  • Chapter DOI: https://doi.org/10.1017/CBO9781139087254.004
Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

  • Humidity
  • Ian Strangeways, TerraData
  • Book: Measuring the Natural Environment
  • Online publication: 05 July 2014
  • Chapter DOI: https://doi.org/10.1017/CBO9781139087254.004
Available formats
×