Published works

Intense heating of air in the vicinity of a bushfire leads to deep ascent. If this ascent is deep enough to lift air above the lifting condensation level, cumulus or cumulonimbus clouds form in a process known as moist pyro-convection. There is abundant anecdotal evidence to suggest that pyro-convective clouds may have a significant impact on fire behaviour by (i) amplifying burn and spread rates (Fromm et al., 2012); (ii) enhancing spotting through plume intensification (Koo et al., 2010; Thurston et al., 2015); and (iii) igniting new fires via pyrocumulonimbus lightning, noting that pyrocumulonimbus lightning conditions favour hotter and longer-lived lightning strikes (Rudlosky and Fuelberg, 2011). Pyro-convective clouds are also responsible for the transport of smoke and other aerosols into the stratosphere, resulting in hemisphere-scale smoke transport and substantial climate impacts (Fromm et al., 2010). Therefore a knowledge of the processes that lead to the generation of moist pyro-convection is important for understanding and predicting fire behaviour, as well as the potential climatic influences of large fires. In this study we use large-eddy simulations to investigate the potential for the generation of moist pyro-convection by bushfire plumes. Firstly we perform simulations over a range of fire intensities and environmental moisture levels. Secondly we repeat a subset of these simulations with differing amounts of moisture released by the fire in order to assess the relative roles of environmental moisture and fire-derived moisture in the formation of pyro-convective clouds.