Synergistic remote sensing of the atmosphere, combined with adaptive techniques, offers unprecedented opportunities to characterise the evolution of key atmospheric features such as the Atmospheric Boundary Layer (ABL). Using long-duration, high-resolution, profiling observations from active and passive ground-based remote sensing systems during the Verification of the Origins of Rotation in Tornadoes Experiment{Southeast (VORTEX-SE) 2017 field campaign, an attempt is made to characterise ABL development over distinct regions that are well known for their relatively high tornado frequency. In this study, observing systems include an S-band radar, Vaisala CL-31 ceilometer, Doppler Wind lidar (DWL) and radiometric observations from the Collaborative Lower Atmosphere Mobile Profiling System (CLAMPS). In this work, ABL height (ABLH) tracking over the diurnal cycle, and - up to a point - its disambiguation over selected non-precipitating case examples, are attempted. Different observational sets are used, namely, radar reflectivity observations assimilated into a Kalman filter, DWL profiles of the vertical velocity, and virtual potential temperature profiles, as well as radiosoundings and cloudbase reference information collected during Intensive Observation Periods (IOP) carried out in VORTEX-SE, Alabama during 2017. Limitations and advantages of each system are discussed.
The Verification of the Origins of Rotation in Tornadoes Experiment Southeast (VORTEX-SE) provides a wealth of long-duration, high-resolution, vertically pointing observations from active and passive ground-based remote sensing systems enabling characterization of the Atmospheric Boundary Layer (ABL) development over distinct regions that are well known for their relatively high tornado frequency. Application of the Extended Kalman Filter (EKF) to BL height estimation in the convective regime (CBLH) of the diurnal cycle from S-band radar reflectivity observations1 has shown to yield accurate results under simple CBL conditions. In this work, we revisit the radar-EKF technique and investigate its main limitations. For example, during daytime clear-sky conditions such as those prevailing in the BL morning transition, weak turbulence leads to very low reflectivity returns, limiting application of this technique. Additionally, turbulent mixing layers capped with a residual layer, and/or multi-layer scenarios can lead the filter to lose track of the BL signature over time. Doppler Wind Lidar (DWL) observations of the vertical wind velocity variance2 provide complementary CBLH estimates to those of the radar-EKF combination, providing potential to disambiguate more complex convective cases. DWL estimates are, however, strongly influenced by the variance threshold selected. The complementarity of radar and DWL for CBLH estimation is studied in reference to radiosoundings.
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