Cooling tower plume rise analyses by airborne lidar

As part of the Atmospheric Studies in Complex Terrain (ASCOT) program, five cooling-tower plume experiments were conducted at The Geysers geothermal area in California during August 1981. The experiments were designed to investigate plume behavior during conditions of valley nocturnal drainage flow and daytime vertical mixing on a mountain ridge. The Airborne Lidar Plume and Haze Analyzer (ALPHA-1) system was used during the experiments to observe plume geometry and aerosol structure of the boundary layer. Subvisible plume rise derived from the backscatter signatures is related to visible plume-rise results recently published. This analysis indicates that the lidar-observed plumes are about 10 times higher than visually observed plumes. The lidar-observed plume rise seemed to correspond with heights of elevated aerosol layers that typically indicate presence of temperature inversions. Pictorial displays are presented which provide information on atmospheric behavior over mountainous terrain.