Comparing the height and area of wild and prescribed fire particle plumes in south-east Australia using weather radar

Abstract

Smoke pollution from landscape fires is a major health issue. Prescribed burning aims to reduce the area and impact of wildfire, but itself produces smoke pollution. This raises the question as to whether the smoke production and transport from prescribed fires is substantially different compared to wildfires. We examined the maximum height, width and areal footprint of large-particle plumes from 97 wild and 126 prescribed fires in south-eastern Australia using the existing network of weather radars. Radar detects large particles in smoke (probably those >100 μm) and hence is an imperfect proxy for microfine (<2 μm) particles that are known to affect human health. Of the 223 landscape fires, ~45% of plumes were detected, with the probability being >0.8 for large fires (>100 000 ha) regardless of type, closer than 50 km from the radar. Plume height was strongly influenced by fire area, the height of the planetary boundary layer and fire type. Plume heights differed between wildfire (range 1016–12 206 m, median 3260 m) and prescribed fires (range 706–6397 m, median 1669 m), and prescribed fires were predicted to be 800–1200 m lower than wildfires, controlling for other factors. For both wildfires and prescribed fires, the maximum plume footprint was always near the ground.