Use of a Large Crane for Wind and Tracer Profiles in an Urban Setting

Abstract

Although measured vertical profiles of wind, turbulence, and tracer concentrations are critical for understanding the urban boundary layer, it is problematic to field a sounding system or a tall structure to support anemometers in a densely populated area. Anemometers mounted on an existing building may be measuring flow distorted by that building. During the Joint Urban 2003 field experiment in Oklahoma City, the authors solved these problems by using a large crane to support a cable and crossarm framework holding a vertical array of eight 3D sonic anemometers. The highest level was over 80 m above the surface; the lowest was just under 8 m. The open-lattice structure of the crane boom and skeletal array framework did not substantially alter the airflow to the sensors. Review of the spectra shows that there are no consistent oscillations in the wind data. Data were accepted from all azimuths, although the flow was from the south 80% of the time. Profiles of wind show pronounced curvature, indicating that the higher levels may be affected by rougher surfaces at a great distance from the crane. This crane-lofted system was safely erected and disassembled in a few hours, stood undisturbed for 34 days, and collected over 1500 separate profiles of 30-min averages.