In situ microphysics observations of intense pyroconvection from a large wildfire

[摘要] This study characterizes the size and shape distributions of 10  µ m to 6 mm diameter particles observed during six penetrations of wildfire-inducedpyroconvection near Boise, Idaho, USA, by a research aircraft over the period29–30 August 2016. In situ measurements by the aircraft include winds,atmospheric state, and bulk water content and particle concentration, size, andshape. These observations are complemented by data from airborne andground-based radars. One of the penetrations is through a subsaturatedsmoke–ash plume with negligible cloud liquid water content that ischaracterized by an updraft of almost 36 m s −1 . The size distributionof number concentration is very similar to that documented previously for asmoke plume from a prescribed fire, and particle shapes exhibit qualitativeand quantitative attributes comparable to ash particles created in a burnchamber. Particles sampled during this penetration are most likelypyrometeors composed of ash. Pyrocumulus clouds are probed in the otherpenetrations where values of relative humidity and cloud liquid watercontent are larger, but updrafts are weaker. Compared to the smoke-plumepenetration, size distributions are mostly characterized by largerconcentration, and particle shapes exhibit a higher degree of circularsymmetry. Particle composition in these pyrocumulus penetrations is mostlikely a combination of hydrometeors (ice particles) and pyrometeors (ash).

[学科分类] 医学（综合）