A lower atmospheric severity index for wildland fires
Document Type: Journal Article
Author(s): Donald A. Haines
Publication Year: 1988

Cataloging Information

  • climatology
  • fire danger rating
  • fire weather
  • fire weather index
  • lapse rate
  • Lower Atmosphere Severity Index (LASI)
  • moisture
  • moisture content
  • season of fire
  • stability
  • stability indices
  • statistical analysis
  • temperature
  • wilderness areas
  • wildfires
  • wildfires
  • wind
Record Maintained By:
Record Last Modified: November 4, 2019
FRAMES Record Number: 11664
Tall Timbers Record Number: 4118
TTRS Location Status: In-file
TTRS Call Number: Fire File
TTRS Abstract Status: Fair use, Okay, Reproduced by permission

This bibliographic record was either created or modified by the Tall Timbers Research Station and Land Conservancy and is provided without charge to promote research and education in Fire Ecology. The E.V. Komarek Fire Ecology Database is the intellectual property of the Tall Timbers Research Station and Land Conservancy.


Dry, unstable air increases the probability that wildland fires will become large and/or erratic. This paper describes an atmospheric index for these fires, based on the environmental lapse rate of a layer of air coupled with its moisture content. In low-elevation regions of the United States, the index is derived from a lapse rate value using 950- to 850-mb temperature differences and a temperature-dew-point spread at 850 mb. At mid-elevations, the index uses 850- to 700-mb temperature differences and the 850-mb temperature-dew-point spread. In the high-elevation western regions, a similar calculation uses a 700- to 500-mb lapse rate value and the temperature-dew-point spread at 700 mb. A preliminary comparison of the low-elevation variant of the index with climatology showed that only 5% of all fire-season days fell into the high-index class. A similar comparison for the high-elevation region showed 6% of all fire-season days in the high-index class , but 45% of days with large and/or erratic wildfire in that class.

[This publication is referenced in the "Synthesis of knowledge of extreme fire behavior: volume I for fire managers" (Werth et al 2011).]

Online Link(s):
Link to this document (3.4 MB; pdf)
Haines, D.A. 1988. A lower atmospheric severity index for wildland fires. National Weather Digest. 13(3):23-27.