Observations of a rotating pyroconvective plume

Background. There is an ongoing need for improved understanding of wildfire plume dynamics. Aims. To improve process-level understanding of wildfire plume dynamics including strong (>10 m s(-1)) fire-generated winds and pyrocumulus (pyroCu) development. Methods. Ka-band Doppler radar and two Doppler lidars were used to quantify plume dynamics during a high-intensity prescribed fire and airborne laser scanning (ALS) to quantify the fuel consumption. Key results. We document the development of a strongly rotating (>10 m s(-1)) pyroCu-topped plume reaching 10 km. Plume rotation develops during merging of discrete plume elements and is characterised by inflow and rotational winds an order of magnitude stronger than the ambient flow. Deep pyroCu is initiated after a sequence of plume-deepening events that push the plume top above its condensation level. The pyroCu exhibits a strong central updraft (similar to 35 m s(-1)) flanked by mechanically and evaporative forced downdrafts. The downdrafts do not reach the surface and have no impact on fire behaviour. ALS data show plume development is linked to large fuel consumption (similar to 20 kg m(-2)). Conclusions. Interactions between discrete plume elements contributed to plume rotation and large fuel consumption led to strong updrafts triggering deep pyroCu.