Lidar measurements of atmospheric flow through a downtown cluster of high-rise buildings

The Joint Urban 2003 experiment was a field study of urban dispersion conducted in Oklahoma City during the summer of 2003. The experiment involved a wide range of instrumentation operating together for 10 Intensive Observation Periods during the month of July. Measurements were taken both for tracer gas and for the associated meteorological fields. The ASU lidar measured both aerosol backscatter and radial velocities fields upwind of the Central Buisiness District (CBD). The lidar was deployed approximately 4 kilometers south of the downtown area with a clear line of sight through downtown building clusters and over several other instrument sites. Joint Urban 2003 presented an opportunity to deploy two matched coherent Doppler lidar systems with close collaboration (between the Army Research Laboratory's and ASU's lidar teams) in operation of the instruments. Data was collected over 28 days in a variety of RHI, PPI, and VAD scan patterns providing inflow conditions and insight into the urban interaction with the mean atmospheric flow for the area south of the CBD. Two periods of mean flow reversal are of particular interest due to a southerly flow which made building wakes clearly observable. During these periods wake meandering and the downstream and cross-stream extents of the wakes are evident. Approximate velocity deficits measured were 2-8 m/s. Possible merging of wakes from separate buildings in the CBD were observed. Steering effects and redirection of the mean flow vectors due to the urban core are also being studied.