Observations of spatial relationships between specific differential phase and lightning flash origins

With the advent of research polarization radars and the imminent polarization of the WSR-88D (Weather Surveillance Radar – 1988 Doppler) network, the possibility now exists to use radar indications of regions within thunderstorms where strong electric fields exist and where lightning is possible as both an operational nowcasting tool and a research tool for cloud electrification studies. Studies have suggested that vertical orientation of ice crystals within thunderstorms may be indicative of strong electrical fields (i.e. 100kV m^-1) within the cloud, possibly leading to lightning. Specific differential phase (Kdp) is a polarimetric radar parameter that can be utilized to give insight into the orientation of hydrometeors within clouds, with positive values suggesting horizontal orientation and negative values suggesting vertical orientation.

This project investigates the spatial relationship between regions of negative Kdp and lightning flash origins, using the CSU-CHILL polarimetric research radar and case studies from June, 2000 during the Severe Thunderstorm Electrification and Precipitation Study (STEPS) field campaign. The Java-based V-CHILL (Virtual-CHILL) utility was utilized in selecting and analyzing potential case studies from the campaign. Lightning Mapping Array (LMA) data was then overlaid with data from the CHILL radar facility to determine any potential spatial relationship between flash origins and negative specific differential phase. Preliminary results will be presented.