Observing Systems

Progress toward characterization of the atmospheric boundary layer over northern Alabama using observations by a vertically pointing, S-band profiling radar during VORTEX-Southeast

Tanamachi, R. L., S. J. Frasier, J. Waldinger, A. LaFleur, D. D. Turner, and F. Rocadenbosch



During spring 2016 and spring 2017, a vertically pointing, S-band Frequency Modulated Continuous Wave radar (UMass FMCW) was deployed in northern Alabama under the auspices of the Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX)-Southeast. In total, ~14 weeks of data were collected, in conditions ranging from quiescent clear skies to severe thunderstorms. The principal objective of these deployments was to characterize the boundary layer evolution near the VORTEX-Southeast domain. In this paper, we describe intermediate results in service of this objective. Specifically, we describe updates to the UMass FMCW system, document its deployments for VORTEX-Southeast, and apply four automated algorithms: 1) a dealiasing algorithm to the Doppler velocities, 2) a fuzzy logic scatterer classification scheme to separate precipitation from nonprecipitation observations, 3) a brightband/melting-layer identification algorithm for stratiform precipitation, and 4) an extended Kalman filter–based convective boundary layer depth (mixing height) measurement algorithm for nonprecipitation observations. Results from the latter two applications are qualitatively verified against retrieved soundings from a collocated thermodynamic profiling system.

A New Technique to Estimate Sensible Heat Fluxes around Micrometeorological Towers Using Small Unmanned Aircraft Systems

Temple Lee, Michael Buban, Edward Dumas, Bruce Baker



Upscaling point measurements from micrometeorological towers is a challenging task that is important for a variety of applications, for example, in process studies of convection initiation, carbon and energy budget studies, and the improvement of model parameterizations. In the present study, a technique was developed to determine the horizontal variability in sensible heat flux H surrounding micrometeorological towers. The technique was evaluated using 15-min flux observations, as well as measurements of land surface temperature and air temperature obtained from small unmanned aircraft systems (sUAS) conducted during a one-day measurement campaign. The computed H was found to be comparable to the micrometeorological measurements to within 5–10 W m−2. Furthermore, when comparing H computed using this technique with H determined using large-eddy simulations (LES), differences of <10 W m−2 were typically found. Thus, implementing this technique using observations from sUAS will help determine sensible heat flux variability at horizontal spatial scales larger than can be provided from flux tower measurements alone.