Single Doppler Radar Measurements of Turbulence Profiles in the Convective Boundary Layer

Abstract

The velocity-azimuth-display technique provides a measurement of the mean wind components above a conically scanning Doppler radar. Wind components are often computed from a least-squares fit of a sinusoid to the Doppler velocity-versus-azimuth data but it is not widely known that information about turbulence can also be obtained from such data. This paper demonstrates that the fluctuations of the measurements about the best-fit sinusoid are related to Reynolds stress components. These fluctuations, when computed about the mean from an ensemble of scans, provide estimates of stress that contain contributions from scales of motion from ?50 m to ?5 km. The method was tested with observations taken by the NOAA/WPL 3.2 and 0.86 cm wavelength radars in the dry, convective boundary layer in which small, naturally occurring particulates were used as tracers of the air motion. Results indicate that continuous profiles of wind and stress components call be produced from heights of about 200 m to the capping inversion (?2000 m) during periods of strong surface heat flux that occur in Colorado during the summer.