Severe convective storms initiated by intense wildfires: Numericalsimulations of pyro-convection and pyro-tornadogenesis

摘要

On the afternoon of 18 January 2003, wildfires sweptthrough several outer suburbs of Canberra (Australia)producing, inter alia, a series of large pyro-cumulonimbuscells and at least one tornado. The results of a large-eddysimulation with a parameterized fire are reported here. Thesimulation, motivated by the Canberra wildfires and severestorms, captures the main characteristics of the observed pyro-cumulonimbi, including the formation of a tornado close towhere one was observed. In addition, the model developsprominent horizontally oriented vortices on the western side ofthe fire in the direction of the low-level shear, and a series ofhorizontally oriented vortices on the upstream side of theconvection column. The production of water by the fire iscritical for the development of a pyro-cumulonimbus cellintense enough to reach the tropopause as observed and plays asignificant role in the associated tornadogenesis.