Criteria for onset of firestorms
Quantitative criteria are evolved for onset of firestorms, severe stationary (nonpropagating) holocausts arising via merger of fires from multiple simultaneous ignitions in a heavily fuel-laden urban environment. Within an hour, surface-level radial inflow from all directions sustains a large-diameter convective column that eventually reaches an altitude of about 10 km (e.g., Hamburg, Dresden, Hiroshima). As the firestorm achieves peak intensity (2-3 hours after the ignitions), inflow speeds are inferred to attain 25-50 m/s; typically 12 km2 are reduced to ashes, before winds relax to ambient levels in six-to-nine hours. Here the firestorm is interpreted to be a mesocyclone (rotating severe local storm). Even with exceedingly large heat release sustained over a concentrated area, in the presence of a very nearly autoconvectively unstable atmospheric stratification, onset of vigorous swirling on the scale of two hours requires more than concentration of circulation associated with the rotation of the earth; rather, a preexisting, if weak, circulation appears necessary for firestorm cyclogenesis.
- Research Organization:
- TRW Space and Technology Group, Redondo Beach, CA (USA)
- OSTI ID:
- 5406597
- Report Number(s):
- AD-P-001804/4
- Country of Publication:
- United States
- Language:
- English
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