5.2 Turbulence velocity spectra and cospectra measured during fire front passage

Wednesday, 19 October 2011: 8:45 AM
Grand Zoso Ballroom Center (Hotel Zoso)
Daisuke Seto, San Jose State University, San Jose, CA; and C. B. Clements, F. Snively, and W. E. Heilman

Atmospheric flow interactions occur at a spectrum of time and length scales. To determine the role fires have on surface boundary layer turbulence, in-situ measurements were made using micrometeorological towers during prescribed fires under different fuels in California, North Carolina, and Finland. Analysis of the data in the frequency domain can give a clear indication of the scales of interaction observed before, during, and after the fire front passage. The normalized spectra and cospectra were compared to previous findings of turbulence spectra characteristics over various atmospheric conditions and environments. Preliminary results indicate that there is a general increase in the spectral density at all ranges of the energy spectrum from the large, lower frequency eddies to the small, higher frequency eddies, suggesting the increased contribution to the overall turbulence generation is accomplished by eddies with multiple sizes. This paper will discuss in more detail the turbulence spectral energy structures that are modified by the fire-induced eddies.
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