Conditions for the start and spread of crown fire

TLDR

The paper discusses factors that govern the start and spread of crown fire in conifer forests, including classification based on crown–ground interaction and modeling the crown fuel as a uniform layer. The authors aim to provide simple criteria for initiating crown combustion and for the minimum rates of spread and heat transfer that allow crown fire to propagate. These criteria are based on thresholds for crown combustion initiation and minimum spread rates and heat transfer into the crown combustion zone. Observations in four types of conifer forest partially support the theory.

Abstract

Some theory and observations are presented on the factors governing the start and spread of crown fire in conifer forests. Crown fires are classified in three ways according to the degree of dependence of the crown phase of the fire on the ground surface phase. The crown fuel is pictured as a layer of uniform bulk density and height above ground. Simple criteria are presented for the initiation of crown combustion and for the minimum rates of spread and heat transfer into the crown combustion zone at which the crown fire will spread. The theory is partially supported by some observations in four kinds of conifer forest.