Evaluating the Benefit and Utility of All-Digital PAR Imaging Modes for Tornadic and Non-Tornadic Supercells using Synthetic PAR Data

Phased array radars (PARs) offer significant improvements over current operational radar capabilities. From rapid-scanning volumetric capabilities reducing scan times to adaptive scanning capabilities and electronic beam steering, PARs remain a logical choice for improving tornado detection in operations. PARs also enable unique scanning strategies such as imaging, with the Atmospheric Imaging Radar (AIR) serving as the first mobile platform to employ imaging techniques and show benefits of simultaneously collected volumetric observations of tornadoes and other severe weather phenomena. Understanding the trade-offs of PAR-enabled scanning strategies like imaging is important for assessing the possible use of such digital beamforming techniques in a future operational PAR network. This study focuses on the application of future operational PAR systems to observe supercell tornadoes and their formation with comparisons to non-tornadic supercells. To understand the impacts of spatial degradation on long-range data and PAR-enabled scanning strategies, we create synthetic PAR observations by resampling archived mobile rapid-scan observations collected by the Rapid X-band Polarimetric radar (RaXPol).

In this study, a synthetic PAR data tool is applied to two tornadic cases (24 May 2011 El Reno, Oklahoma, tornado and the 24 May 2016 Dodge City, Kansas, tornadoes) and one non-tornadic case (17 April 2013 near Lawton/Medicine Park, Oklahoma). Range and azimuth averaging are applied (only in the horizontal due to vertical data limitations in the datasets) over different windows to emulate different standoff ranges more comparable to operational, fixed-site radars. Using dealiased velocity data, intensity of synthetic PAR tornado vortex signatures (TVSs) is analyzed using a measure of the rotational intensity (Delta-V) as a function of time and height for each standoff range as well as for pencil beam scans versus spoiled imaging beams. The impacts of PAR-enabled imaging are analyzed using planned position indicators (PPIs). A comparison of tornadic and non-tornadic cases will be presented to illustrate simulated operational PAR examples. Results indicate that despite increasing standoff ranges and using imaging modes, an operational PAR should still observe a similar mode of tornadogenesis as mobile systems (i.e., non-descending TVS) with a slight delay in observing intensification at increasing standoff ranges. The PAR-enabled imaging mode shows promising results in enabling targeted and more complete data on vertical TVS evolution (through denser vertical sampling). Ultimately, through understanding the meteorological benefits from the synthetic PAR data, we should be able to contribute to improved planning for future all-digital operational PARs and warning decisions for tornadic storms.