Thunderstorm electrification and kinematics as seen through ensemble lightning flash properties



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Previous studies have noted patterns in storm-relative lightning tendencies, with smaller and more frequent flashes closer to updrafts and larger infrequent flashes farther away. These patterns are likely rooted in the variability in charge magnitude and structure across a thunderstorm, which is ultimately derived from the microphysical and kinematic properties present within the storm environment. Therefore, a better understanding of lightning behavior in thunderstorms may give better insight into the kinematic processes present. This study compared local, three-dimensional flash rate and flash size properties to storm structure over a spectrum of storm organizational modes using, for the first time, three-dimensional gridded lightning data. Results showed that some features of the lightning data were common across all storm modes. It was found that the smallest and most frequent flashes were almost always clustered at upper levels of the core regions of convective cells while the largest and usually least frequent flashes in the storm were found far removed from the convective cores. Additionally, the direction of this core to anvil gradient in flash area was found to have only small differences with the 0-8 km bulk shear and storm-relative bulk shear for the MCS cases while storm-relative bulk shear and the mean 6-10 km storm-relative environmental winds had the smallest difference to the flash area gradient direction for the multi-cell and supercell cases. Other interesting features were found unique to only a single storm mode. For multi-cells a spectrum of increased organization of the lightning properties was observed as bulk shear values increased. For the MCS cases a bimodal distribution to the flash extent density was found in the vertical, sometimes only present within the leading line but also sometimes extending well out into the stratiform region. Additionally, the stratiform lightning was often observed to exhibit a sloped structure, down and rearward, from the upper levels of the leading line. The supercell cases exhibited the most amount of variability in flash density and area. Lightning holes were found in all right-moving cases, roughly collocated with bounded-weak echo region on radar. A ring of small and very frequent flashes was sometimes observed to completely surround the lightning hole, or at times would also appear as a broken feature with preferred flanks for maximum flash extent density. This was especially true for the left-moving cells which consistently showed a lack of lightning on their right and forward flanks at low-mid levels, but exhibited distinct maxima in flash extent density on their left and upper flanks. Finally, the smallest and most frequent flashes were always found on the preferred updraft flanks for the left and right moving supercells, with flashes increasing in size and decreasing in rate as you moved along the storm-relative shear vector.



Lightning, Thunderstorm