Observations of the Atmospheric Boundary Layer from a Vertically Pointing, S-band, FMCW Radar in Northern Alabama, during VORTEX-Southeast (2016-2017)

During spring 2016 and spring 2017, a vertically pointing, S-band FMCW radar (UMass FMCW) was deployed in northern Alabama as part of the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX) – Southeast. UMass FMCW collected vertical profiles of both Bragg and Rayleigh scatter at 16-s intervals, at height intervals of 5 m, up to an altitude of 5.1 km. The principal objective of these deployments was to characterize the high spatio-temporal boundary layer evolution near the VORTEX-Southeast domain. In total, 14 weeks’ worth of data were collected, in conditions ranging from quiescent clear skies to severe thunderstorms. In 2017, UMass FMCW was upgraded with a solid state amplifier, replacing the traveling wave tube amplifier used in 2016 and prior seasons. Examples of data collected before and after this upgrade will be shown. We present results of the application of three algorithms to these data: (1) a simple-but-flexible echo classification scheme to separate precipitation from non-precipitation, (2) a bright band identification algorithm, and (3) an extended Kalman filter-based boundary layer height detection algorithm. These results will enable further research regarding drop size distributions (validated using a collocated, ground-based disdrometer) and characterization of the diurnal evolution of the boundary layer over the VORTEX-Southeast domain.