Evaluation of Wildfire Plume Injection Heights Estimated from
Operational Weather Radar Observations using Airborne Lidar Retrievals
Abstract
The vertical distribution of wildfire smoke aerosols is important in
determining its environmental impacts but existing observations of smoke
heights generally do not possess the temporal resolution required to
fully resolve the diurnal behavior of wildfire smoke injection. We use
Weather Surveillance Radar-1988 Doppler (WSR-88D) dual polarization data
to estimate injection heights of Biomass Burning Debris (BBD) generated
by fires. We detect BBD as a surrogate for smoke aerosols, which are
often collocated with BBD near the fire but are not within the size
range detectable by these radars. Injection heights of BBD are derived
for 2-10 August 2019, using radar reflectivity (Z≥10 dBZ) and dual
polarization correlation coefficients (0.2<C.C.<0.9) to study the Williams Flats Fire event. Results show the expected diurnal cycles with maximum injection heights present during the late afternoon period when the fire’s intensity and convective mixing are maximized. Radar and airborne lidar injection height comparisons reveal that this method is sensitive to outliers and generally overpredicts maximum heights by 40%, though mean and median heights are better captured (<20% mean error). Radar heights between the 75th and 90thpercentile seem to accurately represent the maximum, with the exception of heights estimated during the occurrence of pyro-cumulonimbus. Location specific mapping of radar and lidar injection heights reveal that they diverge further away from the fire due to BBD settling. Most importantly, radar-derived injection height estimates provide near continuous smoke height information, allowing for the study of diurnal variability of smoke injections.