The relationship between ground charging and precipitation band structure in continental winter cyclones

Thundersnow is a rare event that occurs when there is a lightning discharge during a snowstorm. Typically, the lightning is generated when bands form in the wraparound region of extratropical cyclones. The bands generate an electric charge both in the cloud level and at the surface. The nature of the electric charge in wintertime precipitation bands is unknown. The surface electric field was measured using an electric field mill (EFM) during the Profiling Of Winter Storms (PLOWS) project, which was conducted in the Midwest of the United States in 2009 and 2010. The EFM was deployed with the Mobile Integrated Profiling System (MIPS) that was typically deployed in the warm frontal or wraparound regions of passing cyclones.

Data on the locations of the lightning strikes in the vicinity of the MIPS were taken from the National Lightning Detection Network (NLDN). WSR-88D Level II radar data were used in conjunction with the NLDN to determine when precipitation bands were in the vicinity of the MIPS EFM and how much lightning was occurring, and whether perturbations in the surface electric field occurred during band passages.

In this presentation, the relationship between the field mill measurements and band passages, and the correlation of electric field change to profiler and radiometer measured variables such as cloud liquid water, snow-to-liquid ratio, and particle vertical velocities will be shown. The likelihood of lightning in the wraparound region of extratropical cyclones will also be determined in the context of other storm variables, such as changes in moisture advection, temperature in clouds, vertical shear, and proximity to storm center.