Tuesday, 16 January 2007: 12:00 AM
Lidar measurements of industrial plumes near an escarpment
207B (Henry B. Gonzalez Convention Center)
In July and August of 2006, a field campaign to measure wind fields and industrial plumes near an escarpment was conducted. The purpose was to develop a fundamental understanding of plume behavior in the vicinity of an industrial facility to provide a scientific foundation for rational prediction and control of pollution exposures of local populations. The experiment took place in Western Australia approximately 100 km south of Perth. In collaboration with the Department of the Environment of Western Australia, Arizona State University deployed its coherent Doppler lidar. The ASU lidar produces 500 pulses per second (2 µm wavelength) and, in conditions prevalent during the experiment, yielded a range of 7 – 8 km. The lidar was positioned southwest of the plant in order to observe plume movements toward a township approximately 4 kilometers to the south. A wide variety of other instrumentation was deployed, including 2 Proton Transfer Reaction Mass Spectrometers (PTRMS), 1 sodar, radiosondes, a fast response portable GCMS, a flux tower, continuous NOx, CO2, and CO analysers, a ceilometer, three meteorological stations, an array of Tapered Element Oscillating Microbalances (TEOMs), canister samplers, and teams of odor assessors. During some measurement periods, low elevation angle, Plan-Position-Indicator (PPI) scans show plumes from the plant travelling downstream 4-5 km over the township. In order to scan above ground-clutter, a minimum elevation angle of approximately 2.5 degrees was used, raising issues of the representativeness of lidar-sensed plumes for assessing ground level activity. Attempts to associate ground-level in situ measurements with plumes detected by the lidar will be presented. Atmospheric scenarios predicted through modelling to be relevant for possible plume downstrikes will be evaluated. In particular, the role of the nearby escarpment in shaping flow conditions such as recirculations and shear layers appears to be crucial for understanding how elevated plumes may be transported downward.