An atmospheric index used to indicate the potential for wildfire growth by measuring the stability and dryness of the air over a fire.
The Haines index (or lower atmospheric severity index) is a fire weather index based on the stability and moisture content of the lower atmosphere. It is intended to measure the potential for existing fires to become large fires or behave erratically. It does not incorporate any wind information and is not appropriate for use in windy situations. Stability and moisture are determined for a layer elevated above the ground at prescribed pressure levels. For low elevation areas, the 950- and 850-mb levels are used; midelevations use the 850- and 700-mb levels; high elevations use 700 and 500 mb. Stability across these levels and moisture at one of the levels are each converted to a 1, 2, or 3 and the two numbers added. A Haines index of 2 or 3 is “very low,” 4 is “low,” 5 is “moderate,” and 6 is “high.”
Haines Index has been defined 4 different ways in documents like Forests and Rangelands Glossary of Terms, Glossary of Wildland Fire Terminology, Glossary of Meteorological Terms, and 1 more.