High resolution profiling of the atmospheric boundary layer

The University of Massachusetts Microwave Remote Sensing Laboratory developed a low cost, high-resolution S-band FM-CW radar profiler to study the structure and dynamics of clear-air turbulence in the atmospheric boundary layer. The radar system resolves the vertical reflectivity structure of the boundary layer with 2.5 m resolution. The radar employs a 250 W transmitter and a pair of parabolic dish antennas with 34 dB gain. In October 1999, the S-band profiler was deployed near Wichita, KS for the 1999 Cooperative Atmosphere-Surface Exchange Study (CASES'99) Nocturnal Boundary Layer experiment. Throughout this experiment it produced real-time imagery of a variety of boundary layer features including Kelvin-Helmholtz instabilities, gravity waves, and clear-air convection. Real-time images were used to guide research aircraft to sample these features with on-board instrumentation. In addition to clear-air (Bragg) returns, the radar often observed significant scattering from insects and birds. The distribution of insect scatter appears to reveal additional boundary layer structure not otherwise detectable at S-band. This paper describes the radar system and presents highlights of the profiler measurements collected during the experiment.