Evidence for eddy-scale control of lightning flash sizes using the West Texas Lightning Mapping Array and TTUKa radars

Recent work by Bruning and MacGorman (2013) proposed an energetic measure of lightning flashes based on flash size (area) and rate. The resulting energy spectrum as a function of flash size had a consistent shape, with an apparently linear scaling regime at the same length scales where a turbulent thunderstorm's inertial subrange would be expected. They hypothesized that electrical potential, which controls the extent of lightning channels, was organized by the (sometimes) turbulent character of the convective flow. Lacking in that study were data with which to make the comparison between the electrical and kinematic energy spectra.

This study presents data from field trials with the TTU Ka-band mobile doppler radars and the West Texas Lightning Mapping Array (WTLMA). Intersecting vertical cross sections from the radars (every 10 s at 0.33 deg beamwidth and ~12 m gate spacing) clearly resolved the turbulent kinematics, as seen in both the texture of Doppler velocities and values of spectrum width. Trackable patterns in time series of those fields appeared to provide additional signal about the atmospheric fluid's motion. More turbulent regions tended to have the smallest flashes, and vice versa. These data are being used to refine plans for The Kinematic Texture and Lightning (KTAL) Experiment, which will be conducted in 2015-16 to formally quantify the turbulent kinematics and test for their covariance with flash sizes mapped by LMAs.