Incorporating Vertical Winds into PHOENIX RapidFire's Ember Dispersal Model

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Fire Behaviour
Fire Weather
TitleIncorporating Vertical Winds into PHOENIX RapidFire's Ember Dispersal Model
Publication TypeReport
Year of Publication2012
AuthorsChong, D, Tolhurst, KG, Duff, TJ
Date Published12/2012
AbstractPHOENIX RapidFire is a fire simulation model developed in Australia as part of the Bushfire CRC. One unique aspect of the modelling process is the way spotfires are modelled and incorporated into fire spread. Part of the spotting process requires modelling of ember release, transport and spotfire ignition. In the first iteration of spotfire modelling, surface wind (10 m in the open) was used to estimate the distance and spread of embers falling ahead of a fire. However, it is acknowledged that upper-winds usually differ in speed and direction from surface winds. It was therefore thought that that fire modelling could be improved by using the wind speed and direction data produced by the numerical weather prediction models. PHOENIX was modified to incorporate multi-level wind data, however, the forecast data had an uncorrected bias that results in incorrect ember transport modelling results. The lack of systematic, high resolution and comprehensive upper-wind observations makes bias correction and fire model testing impossible at the current time. It was therefore not possible to develop an improved ember transport model for PHOENIX. This report describes the process and results obtained from this research. In the end, a version of PHOENIX that can use a single layer of upper-wind data as input was developed. This will allow some theoretical testing of PHOENIX, but cannot be used for operational fire predictions with the currently available data.