Publication Date

Fall 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Meteorology and Climate Science

Advisor

Craig Clements

Keywords

Doppler radar, Dynamics, Plume, Pyroconvection, pyrocumulus, Wildfire

Subject Areas

Meteorology; Atmospheric sciences; Environmental science

Abstract

During a period of explosive growth of the Pioneer Fire (Idaho, August 2016), deep pyroconvective plumes were sampled by aircraft. The research aircraft was equipped with both remote sensing and in situ instrumentation, including a W-Band Doppler radar which provided high-resolution vertical velocity retrievals from within the developing pyrocumulus. Being the first direct observations of vertical velocity within a pyrocumulus cloud, they have provided unique insights into the dynamical processes governing pyroconvective environments, with important implications for the fire modeling community. The observations were quality-controlled and corrected for issues such as Doppler velocity aliasing, and the plume’s kinematic structure was examined and contextualized using flight-level and surface thermodynamic data collected by the Boise National Weather Service, RAWS observations, and NEXRAD radar-derived plume echo tops. The analyses indicated an extreme pyroconvective environment, with updrafts approaching 60 m s-1 several kilometers above ground level. Interestingly, the observations yielded no secondary peak in vertical velocity aloft linked to latent heat release from condensation. Moreover, updraft magnitude was found to increase with height above the surface and below the condensation level. A wide updraft core acting to isolate the plume center from lateral entrainment processes is hypothesized as a possible explanation for the observed characteristics of the vertical velocity profiles.

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