Canadian Forest Service Publications
Relative humidity measurement for fire danger rating in Canada. 1989. Flannigan, M.D.; Litwin, P.J. Forestry Canada, Petawawa National Forestry Institute, Chalk River, Ontario. Information Report PI-X-93. 12 p.
Available from: National Capital Region
Catalog ID: 11737
Series: Information Report (Petawawa)
Wet and dry bulb temperatures from ventilated and non-ventilated screens can be used to obtain realistic values of relative humidity provided the appropriate psychrometric coefficient is used. However, relative humidity from non-ventilated screens are subject to significant error when the weather is sunny or calm.
Our investigations revealed that thermohygrometers are poor for field measurement of RH whereas the PCRC-11 sensor and Vaisala humicap performed well.
There is a need for a sensitivity study of the Fire Weather Index with respect to relative humidity. We would also suggest the relative humidity lookup table be replaced by the Goff-Gratch equation. Finally, alternatives like using dewpoint temperature to obtain relative humidity or automating the system should be investigated.
Also available under the title:
Mesure de l'humidité relative pour l'évaluation des risques d'incendie au Canada (French)
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