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Measures of Stability


Major Factors

Primary Utility


Davis Stability Index

Lapse rate

Basic measure of stability

Southeast US

Ventilation Index

Mixing height and transport wind

Smoke dispersion

United States

Haines (Lower Atmospheric Stability) Index

Lapse rate and relative humidity

Large fire growth potential

United States

Pasquill Stability Index

Solar radiation, cloud cover and surface wind speed (surface based stability)

Smoke dispersion


Lavdas Atmospheric Dispersion Index

Pasquill, mixing height, transport wind

Smoke dispersion and fire growth potential.


The Lower Atmospheric Severity Index (commonly known as the Haines Index) was developed during the 1980s as a fire weather tool to estimate the effect of atmospheric dryness and stability on the growth potential of a wildfire. The goal was to identify typical combinations of humidity and stability and contrast them with combinations of stability and humidity prevalent during problem fire outbreaks. Always reference local Climatology (below).

Haines Index Calculation Criteria

LOW ELEVATION Stability Term (A)

LOW ELEVATION Moisture Term (B)

950 – 850 mb °C

A = 1 when 3°C or less

A = 2 when 4-7°C

A = 3 when 8°C or more

950 mb T° C – 950 DP° C

B = 1 when 5° C or less

B = 2 when 6-9° C

B = 3 when 10° C or more

MID ELEVATION Stability Term (A)

MID ELEVATION  Moisture Term (B)

850 – 700 mb °C

A = 1 when 5°C or less

A = 2 when 6-10°C

A = 3 when 11°C or more

850 mb T° C – 850 DP° C

B = 1 when 5° C or less

B = 2 when 6-12° C

B = 3 when 13° C or more

HIGH ELEVATION Stability Term (A)

HIGH ELEVATION  Moisture Term (B)

700 – 500 mb °C

A = 1 when 17°C or less

A = 2 when 18-21°C

A = 3 when 22°C or more

700 mb T° C – 700 DP° C

B = 1 when 14° C or less

B = 2 when 15-20° C

B = 3 when 21° C or more

Haines Index (A + B)

Potential for Large Fire

2 or 3




Very Low




US Haines Elevation Classification Map

The Haines, or Lower Atmospheric Stability Index, uses different inputs based on the general classification of terrain elevation.  This map displays areas of High, Mid, and Low elevation areas.

Haines Index Climatology