Introduction

PHOENIX RapidFire users reported that the 'burnt area' output generated by a single run of PHOENIX is sensitive to minor changes in inputs or operating conditions. Fire Prediction Services had Stock Software investigate the following user reported issues:

• Marginal changes in the point-of-origin can result in significant variation in the burnt area generated;

• Different isochrone settings result in different burnt area results;

• Dynamic time stepping is sensitive to weather and isochrones creating different results;

• Identical projects + data can produce different outputs when run on different computers; and

• There are issues with suppression predictions with 'jumping' behaviorbehaviour.

This technical note summarises the sensitivity testing and includes recommendations to users.

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Various users had reported unexpectedly significant variation in the total 'burnt area' produced by PHOENIX simulation runs based on small or marginal changes in initial conditions. Fire Prediction Services requested Stock Software to formally investigate the issues reported.

Stock Software undertook a significant level of sensitivity testing that specifically addressed the user concerns and tested various theories pertaining to the causes of the variations.

Fire Prediction Services reported the findings of the sensitivity testing to the PHOENIX Technical Reference Group (TRG). The TRG issued recommendation to address the issues.

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