Investigation of influence of fuel moisture content on surface fire transition to crown fire using physics-based modelling

Background The transition from surface fire to crown fire depends on various factors, including atmospheric conditions and forest characteristics. Aims In this study, we investigate the role of fuel moisture content in the transition from surface fire to crown fire in a pine forest using the physics-based model Fire Dynamics Simulator. Methods Building on our previous work, which examined the effects of wind speed and crown base height (CBH) in a dry forest with a 5% moisture content, we expand the analysis to include higher moisture levels of 10% and 13%. In addition to varying moisture content, we conducted simulations of various scenarios by changing wind speed and CBH to study the interaction between these factors in the surface fire transition. Key results Simulations revealed that increasing the moisture content significantly reduces crown mass loss and vertical flame penetration, with the most notable reduction occurring for 5–10% moisture content. At lower moisture levels, enhanced convective activity and vertical flame development were observed, which facilitated the initiation of crown fire. Conclusions The results confirm that moisture acts as a thermal barrier and natural limiter of the transition from surface to crown fires. Implications These findings emphasise the need for accurate fuel moisture data in wildfire prediction and risk mitigation models.