Concurrent FM-CW Radar and Lidar Observations of the Boundary Layer

Abstract

Boundary layer probing by multiple remote sensors can greatly improve the understanding of processes in this complex region. For this purpose one needs to know the unique information each individual sensor can provide. Two promising boundary layer remote sensors, a microwave, frequency-modulated, continuous-wave (FM-CW) radar and a laser radar (lidar), were operated simultaneously to probe a common volume. As expected, the lidar sometimes separately detected aerosol layers, notably cloud bases, and the radar sometimes separately detected refractive layers and insects. Boundaries of aerosol structures were often found to be regions of radar returns such as in layers, convective activity, and breaking waves. In contrast, however, a refractive layer was observed within an apparently well-mixed aerosol layer. The data indicate that the radar may have a characteristic echo which is coincident with cloud and fog tops. This experiment shows that FM-CW radars and lidars can separately sense layering in the boundary region and that they provide complementary information on boundary layer mixing processes.