Linking local wildfire dynamics to pyroCb development

Abstract

Extreme wildfires are global phenomena that consistently result in loss of life and property and further impact the cultural, economic and political stability of communities. In their most severe form they cause widespread devastation of environmental assets and are capable of impacting the upper troposphere/lower stratosphere through the formation of a thunderstorm within the plume. Such fires are now often observed by a range of remote-sensing technologies, which together allow a greater understanding of a fire's complex dynamics. This paper considers one such fire that burnt in the Blue Mountains region of Australia in late November 2006, which is known to have generated significant pyrocumulonimbus clouds in a series of blow-up events. Observations of this fire are analysed in detail to investigate the localised processes contributing to extreme fire development. In particular, it has been possible to demonstrate for the first time that the most violent instances of pyroconvection were driven by, and not just associated with, atypical local fire dynamics, especially the fire channelling phenomenon, which arises due to an interaction between an active fire, local terrain attributes and critical fire weather and causes the fire to rapidly transition from a frontal to an areal burning pattern. The impacts of local variations in fire weather and of the atmospheric profile are also discussed, and the ability to predict extreme fire development with state-of-the-art tools is explored.