A Comparison of Dual-Polarimetric Radar Variables in Two Lake-Effect Storms With and Without Lightning During the Lake-Effect Electrification (LEE) Project

One of the aims of the Lake-Effect Electrification (LEE) Project, which was undertaken from September 2022 to March 2023 on the east shore of Lake Ontario, is to define environmental and radar-based thresholds for lightning in lake-effect storms. Dual-polarimetric radar variables, including reflectivity, differential reflectivity and specific differential phase from lake-effect events are analyzed from two intensive observation periods (IOPs) – one with lightning, on 20 Nov 2022, and one without lightning, on 19 Dec 2022 – to form and test baseline radar variable characteristics for electrification in cool-season lake-effect storms. Data from the X-band Doppler on Wheels, KTYX WSR88-D S-band radar, and the NSSL and Georgia Tech lightning mapping arrays are leveraged to make inferences about precipitation particles and to determine when lightning strikes occurred.

Both storms are shown to have regions with enhanced reflectivity and specific differential phase indicating convective cells and dendrites within the storms, and both have ground observations of graupel precipitation, albeit with larger particles in the lightning case. The lightning case is also found to have a distinctive negative differential reflectivity streak on both the PPI and RHI cross-sections at about 2 km MSL 6 minutes before a nearby lightning strike, suggesting dendritic clumps or graupel, while the non-lightning storm had relatively uniform differential reflectivity. In addition, the cloud top heights are about a kilometer higher in the lightning case, confirming conclusions of previous studies that sufficient cloud top height is necessary for thundersnow.