Investigation of optical characteristics and smoke-plume dynamics in the wildfire vicinity with lidar

Basic results of a comprehensive investigation of the potential and restrictions of the remote sensing lidar technique in smoke-polluted atmospheres made in the Missoula Fire Sciences Laboratory (FSL) are presented. The study is based on the three-year lidar measurements of dynamics and optical characteristics of smoke plumes originated in prescribed bums and wildfires. For the measurements, a mobile two-wavelength scanning lidar was used. The lidar operated in the vertical scanning mode and in a combined vertical-azimuthal mode and provided detailed, range-resolved information on the smoke particulate loading up the distances and heights of 5 - 10 km from the lidar. The lidar was successfully used for the real-time determination of smoke plume dispersion, its top heights, and spatial boundaries. In some cases, the measured smoke plume tops reached heights of more than 8 km above ground level. The lidar measurements close to large wildfires also revealed numerous cases of a multilayered atmosphere with well-defined horizontally stratified smoke layers, generally, at heights between I and 3 km, originating in morning inversions and then sustained by the solar heating of the layers. The time series measurements allowed monitoring of their temporal transformation, including the downdraft transport of the smoke particulates to ground level. Special measurement methodology and data processing techniques for the smoke-polluted atmospheres were developed. This made it possible to obtain accurate vertical profiles of the optical characteristics of the smoke particulates, such as optical depth, and the backscatter and extinction coefficients.