21C.1 Exploration of Radar-Based Algorithms to Develop a Climatology of Warm Season Horizontal Convective Rolls

Thursday, 31 August 2017: 11:00 AM
St. Gallen 1&2 (Swissotel Chicago)
John R. Banghoff, Pennsylvania State Univ., Univ. Park, PA; and M. R. Kumjian and D. J. Stensrud

Horizontal convective rolls (HCRs) are counter-rotating vortices in the planetary boundary layer that typically align within 30° of the mean wind and have horizontal spacing of 2-8 km. HCRs influence convective initiation through interaction with other boundaries, such as fronts, sea breezes, or outflows from previous convection, and have been implicated in tornadogenesis in supercells. HCR-like features have been observed in convection-allowing model output as grid spacing decreases, approaching the size of HCR wavelengths. Although a number of individual case studies have been conducted to determine HCR characteristics, little is known about the mean climatology and monthly variation of HCRs. A 10-year warm-season (April through September) analysis of HCR activity in central Oklahoma is being conducted using polarimetric WSR-88D clear-air observations and Rapid Refresh analyses to determine typical HCR orientation angle, aspect ratio, lifetime, and times of formation and decay. To facilitate the rapid processing of radar scans, several algorithms are being developed and tested to automatically detect reflectivity and velocity characteristics of HCRs. These include Fourier transforms, Velocity Azimuth Display (VAD) departure analysis, and image processing/machine learning. A variety of HCR events will be presented, to illustrate their similarities and differences, as well as early results from automated HCR detection techniques.

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