Vertical distribution of nighttime smoke following a wildland biomass fire in boreal Alaska

Abstract

A comprehensive evaluation of the vertical structure of a smoldering smoke plume was afforded by a unique combination of tethersonde measurements (from ground level to about 400 m above ground level (AGL) or 274–674 m above sea level (ASL)), lidar sounding (from about 1.5 to 5 km ASL), and a video recording during the FROSTFIRE experimental burn in July 1999. Tethersonde and lidar measurements were made at local midnight. The video camera operated continuously for 1 week. Estimates of mass concentration were derived from the light‐scattering measurements. Every night, upper level smoke concentrations were estimated to be about 1000 times lower than near‐surface concentrations. The tethersonde instrument indicated maximum mass concentrations on the night following the most active burning (10–11 July), with the smoke trapped below an inversion at 115 m AGL. The lidar measurements indicated that maximum mass concentrations aloft (∼2000 m AGL) occurred on the next night (11–12 July), when the inversion was weaker, and estimated mass concentrations in the first few hundred meters ASL were smaller. The opportunistic combination of instruments offers the first available quantitative information on vertical plume structure in smoldering biomass smoke and holds promise for more a rigorous understanding of smoldering smoke as it significantly impacts visibility and human health.