The dependence of modes of propagation of quasi-linear convective systems on the boundary layer: A multi-sensor analysis

This paper presents multi-sensor observational analyses of quasi-linear convective systems (QLCS, which include rain bands, squall lines, and bow echoes) and focuses in particular on the pre-storm boundary layer and its impact on the mode of propagation. The primary data sources are derived from instruments located in the Huntsville, Alabama region, including a dual polarization Doppler radar, adjacent WSR-88D radars, a 915 MHz boundary layer wind profiler, a Doppler sodar, a 12-channel microwave profiling radiometer, and surface data. These instruments provide a representation of the pre-storm environment (static stability and wind profiles), and radar measurements of boundary layer fine-lines and internal storm structures. The observations suggest that ducted gravity waves and internal bores, in addition to density currents, are sometimes located at the leading edge of propagating QLCS's. The classification of density current, gravity wave, or internal bore is greatly facilitated by radiometric soundings of the lower atmosphere, which are acquired at 60-s time intervals, as well as by wind profiles provided by the wind profiler. Examples of each type of QLCS (bore, gravity wave and density current) will be presented. The internal structure of QLCS in these cases will be compared, and related to the dynamics of density currents, internal bores, and gravity waves.