Energy Release Component (ERC)

Description

The Energy Release Component (ERC) is an index which is related to the potential heat released at the flaming front of a fire measured in units of available energy per square foot. This index can be converted to the available energy per unit area within the flaming front at the head of a fire (in units of BTU/sq. ft) by multiplying the index by a factor of 25. ERC is a commonly used fire danger index by fire management in the United States for tracking the fire season and serves as a guide for fire suppression and fuel treatment operations. The ERC is one of the outputs of the National Fire Danger Rating System (NFDRS, Bradshaw et al., 1983) that represents the cumulative drying effect of daily meteorology on both live fuel moistures and 100 and 1000-hour dead fuel moistures and is considered a build-up index as it’s values are carried over from day to day. As such, ERC generally tracks within season moisture specific to fuels that can potentially carry fire and thus represents concurrent moisture stress rather than longer-time drought stress like PDSI. ERC is most sensitive to variations in relative humidity and precipitation, but does not incorporate the influence of wind speed. We use a common fuel model (model G, or dense confer stand with heavy litter accumulation) in ERC calculations for consistency across space as well as its frequent use by regional fire management. ERC values are best viewed as either percentiles or anomalies from the historic value for individual locations as a value of ERC=60 can represents very different relative conditions from place to place. 

References

Bradshaw, L.S., R.E. Burgan, J.D. Cohen, and J.E. Deeming. 1983. The 1978 National Fire Danger Rating System: Technical Documentation. USDA Forest Service; Intermountain Forest and Range Experiment Station, General Technical Report INT-169, Ogden, Utah. 44 pp. http://www.fs.fed.us/rm/pubs_int/int_gtr169.pdf