Thresholds of surface fire transition to crown fire: Effects of wind speed and crown base height with fixed moisture content

Forest fires present significant global risks, leading to loss of life, community displacement, and extensive damage to property and the environment, with substantial economic and social consequences. Propagation of wildland fires can be divided into two categories: surface and crown fires. This study aims to identify threshold parameters that influence the transition from surface to crown fire, helping fire managers prevent manageable fires from escalating into uncontrollable crown fires. This study conducted pine forest simulations using the physics-based fire model Fire Dynamics Simulator (FDS) to examine the effects of varying wind speeds and crown base heights on fire transition. The results identify that 80 % crown mass loss represents sustained crowning, while values between 65 % and 80 % correspond to intermediate crowning. Furthermore, the findings demonstrate that wind speed and crown base height are crucial in reaching these threshold values. A reduction in crown base height substantially increases the likelihood of sustained crowning. However, the influence of wind speed on the surface fire transition varies with crown base height. These findings enhance understanding of surface fire transition and offer valuable insights for forest fire management and prevention.