The potential for wild land fire depends on both fuel loads and on atmospheric conditions. Prior research on temporal variations in fire regimes has primarily focused on fuel loads, and in general has neglected the atmospheric component of fire risk. In contrast, this study specifically investigates the historical variations and potential future changes in the atmospheric potential for large or dangerous fires in North America. The Haines Index, a frequently used tool in wildfire weather forecasting and monitoring, is used as an indicator of the atmospheric potential for fire. Introduced in 1988 as the “Lower Atmospheric Severity Index,” the Haines Index characterizes the potential impact of dry, unstable air on wildfires and is calculated from temperature and dewpoint in the lower troposphere. The index values range from 2 (low risk) to 6 (high risk), and the index has three different versions (referred to as the “low,” “mid,” and “high” Haines Index) that consider differences in surface elevation.

This research project has three main components:

Evaluation of Computational Methods for the Low Elevation Haines Index.
The Haines Index was designed to use readily available observations from upper air soundings. The original formulation of the “low” elevation version of the index used temperature and humidity observations at 850 hPa, which is a “mandatory” sounding level, and temperature observations at 950 hPa, which, although not an official mandatory level, was a regularly reported pressure level at that time. In 1991 the National Weather Service implemented a new mandatory level for radiosonde observations at 925 hPa, and subsequent to this measurements at 950 hPa became much less frequent. Somewhat surprisingly given the popularity of the Haines Index, there has not been a coordinated, standardized modification of the low version of the Haines Index to accommodate this change. As part of this project, alternative approaches for calculating the low elevation version of Haines Index are compared to the original formulation.

Historical Climatology of the Haines Index for North America.
A comprehensive, long-term climatology of the Haines Index is lacking. To address this need, a 40-year (1961-2000) climatology for North America is being constructed using temperature and humidity fields from the National Centers for Environmental Prediction/ National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The climatology will be in the form of an electronic atlas that focuses on the variations in the frequency and persistence of the Haines Index at annual and seasonal time periods.

Potential Future Changes in the Atmospheric Component of Fire Risk. 
Several researchers have considered how fuel loads may change in the future, but potential future changes in atmospheric stability and humidity have received little attention. The Haines Index will be calculated from future simulations from several General Circulation Models (GCMs) and from a regional climate model (MM5) that is driven by a larger-scale GCM. The projected values of the Haines Index will be used to evaluate the sensitive of current Haines Index patterns to a changing climate and to assess the range of uncertainty associated with projections of the Haines Index for a future climate.


This research is being conducted by climatologists, meteorologists, and computer scientists at Michigan State University and the U.S. Forest Service North Central Research Station.


Rick Ochoa, National Fire Weather Program Manager, National Interagency Coordination Center, Boise, ID


This research is funded by the Joint Fire Science Program.