Airborne Doppler Radar Observations of PyroCu/Cb Plume Kinematics and Thermodynamics during the 2016 Pioneer Fire in Idaho

During a two-day period in August 2016, the University of Wyoming King Air sampled deep pryoconvenctive plumes, including developing pyrocumulus (pyroCu), generated by the Pioneer Fire in Idaho. The aircraft was equipped with both remote sensing and in situ instrumentation, including a W-Band Doppler radar, LiDAR, infrared thermometer, and multiple cloud microphysics probes. The radar’s beam configuration allows for retrieval of the vertical velocities within the plume both above and below the aircraft. The in situ and radar observations collected during the aircraft plume penetrations and overpasses are presented.

Preliminary analyses indicate an extreme pyroconvective environment with updrafts of 37 m s^-1 and significant temperature perturbations recorded with in situ probes during an aircraft penetration of the developing pyroCu at an altitude greater than 5 km MSL. The radar analyses show broad areas of high-velocity (>30 m s^-1) updrafts, with localized extreme pyroconvective updrafts approaching 60 m s^-1. The maxima in vertical velocity were often located several kilometers above ground level, suggesting the plume dynamics were driven by both fire-generated buoyancy and subsequent condensation aloft. Vigorous downdrafts along the plume edges were also observed. Other interesting aspects of the pyroCu penetration include surprisingly small values of liquid water content and cloud droplet concentration. The plume’s observed kinematic, thermodynamic, and cloud structure are further examined and contextualized using upper-air data collected by the Boise National Weather Service forecast office, RAWS surface observations, and KCBX NEXRAD radar-derived plume echo tops, which reached to 16 km MSL.