Differences in Fire Danger with Altitude, Aspect, and Time of Day

Publisher： Society of American Foresters

ISSN： 0022-1201

Source： Journal of Forestry, Vol.40, Iss.4, 1942-04, pp. : 318-323

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Abstract

The measurement of fire danger has progressed remarkably since the early days of measuring humidity alone, or humidity and wind, or humidity, wind, and rain at a few valley bottom stations scattered widely apart over a forest of a million acres or more. Measuring the moisture content of the fuels directly is now known to be more accurate than measuring humidity and rain and then estimating the fuel moisture and inflammability. Other factors, such as the shade of timber canopies of different densities, north--versus south--facing slopes, valley bottom versus ridge top or mountain top exposure, the greenness of vegetation, etc., are also now being recognized as significant. Obviously, all significant factors deserve careful consideration if danger ratings of any kind are to be used most effectively by field men. The hope or dream of one single, simple factor to be measured only once or twice each day at one station as a criterion of fire danger over a large area has now been completely abondoned in most forest regions. Forest fire danger is "not that simple." Furthermore, the protection of our forest resources from fire is now recognized to be of great enough importance to warrant much more than one measurement per day at one or two stations per million acres to determine what measures must be applied to safeguard them from destruction.