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Adjustment of relative humidity and temperature for differences in elevation.

Informally Refereed

Abstract

The variation of fire-weather elements in mountainous terrain is complex at any one time, and the patterns vary considerably with time. During periods of serious fire weather, this variation becomes important. Much information is obtainable by local interpretation of available forecasts and observations. Optimum use of available information requires some understanding of basic meteorological processes and also demands adequate tools for application of the principles.

This paper provides information about variation of midafternoon temperature and relative humidity in mountainous terrain and explains the use of two charts that help in estimating the amount of variation. For layers of air in contact with the surface, the charts make it possible to:

1. Determine the vertical extent of layers in which mixing is present (unstable layers) and of layers in which there is no mixing (stable layers).
2. Adjust temperature and humidity between elevations within mixed layers.
3. Predict afternoon valley temperatures and humidities from morning observations at peak stations.
4. Estimate humidities at any level within the mixed layer beneath cumulus clouds.

Citation

Cramer, Owen P. 1961. Adjustment of relative humidity and temperature for differences in elevation. Res. Pap. PNW-RP-043. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station: 1-21
https://www.fs.usda.gov/research/treesearch/25484