Stability
Measures of Stability
| Index | Major Factors | Primary Utility | Application |
|---|---|---|---|
| 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 | SASEM |
| Lavdas Atmospheric Dispersion Index | Pasquill, mixing height, transport wind | Smoke dispersion and fire growth potential. | Florida |
Lower Atmospheric Stability (Haines) Index
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, see 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 4 5 6 | Very Low Low Moderate High |
U.S. Haines Elevation Classification Map
Haines Index Climatology
PRINT FBFRG Stability
Page Last Modified / Reviewed:
2021-07-08