Combining Interferometer, LMA, and ΔE measurements on positive cloud-to-ground flashes over Langmuir Laboratory

Abstract:

Positive cloud-to-ground (+CG) lightning flashes are considerably less
common than -CG flashes, and the +CG/-CG ratio has a geographical
dependence. +CG flashes are much more common in supercell storms in Oklahoma
and Colorado, for example, than in the small convective cells
characteristic of New Mexico mountain storms.
Since +CG flashes in New Mexico are relatively rare, they have been much
less studied here. In this study, we combined a digital interferometer
(INTF) operating in the 20--80~MHz band with cost-reduced flat plate
antennae (based on the recently published design by Stock, et al.) with
a lightning mapping array. The INTF provides only 2-dimensional maps of
lightning, but can be interpolated to 3-D with the integration of lightning
mapping array (LMA) data. Finally, we combined ΔE-field
(slow-antenna) sensors to characterize the gross charge motion of the
flashes (and pre-select positive CG candidates).

By combining these data sets, we expect to learn more about the
relationship between continuing current and M-components during CG flashes
and the in-cloud activity associated with these phenomena. Early results
seem to indicate that positive CG's with continuing currents reveal channel
growth in the clouds associated with the production of continuing current.
This stands in contrast to prior findings on negative CG's which showed no
correlation between in-cloud channel development and the presence or
absence of continuing current.