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Harrison, R. G. 
ORCID: https://orcid.org/0000-0003-0693-347X and Wood, C. R.
(2012)
Ventilation effects on humidity measurements in thermometer screens.
Quarterly Journal of the Royal Meteorological Society, 138 (665).
pp. 1114-1120.
ISSN 1477-870X
doi: 10.1002/qj.985
Abstract/Summary
Relative humidity (RH) measurements, as derived from wet-bulb and dry-bulb thermometers operated as a psychrometer within a thermometer screen, have limited accuracy because of natural ventilation variations. Standard RH calculations generally assume a fixed screen psychrometer coefficient, but this is too small during poor ventilation. By comparing a reference humidity probe—exposed within a screen containing a psychrometer—with wind-speed measurements under controlled conditions, a wind-speed correction for the screen psychrometer coefficient has been derived and applicable when 2-metre wind speeds fall below 3 ms–1. Applying this to hourly-averaged data reduced the mean moist RH bias of the psychrometer (over the reference probe) from 1.2% to 0.4%, and reduced the inter-quartile range of the RH differences from 2.0% to 0.8%. This correction is particularly amenable to automatic measurement systems.
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| Item Type | Article |
| URI | https://centaur.reading.ac.uk/id/eprint/24582 |
| Identification Number/DOI | 10.1002/qj.985 |
| Refereed | Yes |
| Divisions | Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology |
| Uncontrolled Keywords | Psychrometer; hygrometer; wet-bulb; automatic weather station; supercooling. |
| Publisher | Royal Meteorological Society |
| Publisher Statement | This is a preprint of an article accepted (November 2011) for publication in Quarterly Journal of the Royal Meteorological Society Copyright ©2011,2012 Royal Meteorological Society |
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