Analysis of blue corona discharges at the top of tropical thunderstorm
clouds in different phases of convection
Abstract
We report on observations of corona discharges at the uppermost region
of clouds characterized by emissions in a blue band of nitrogen
molecules at 337 nm, with little activity in a red band of lightning
leaders at 777.4 nm. Past work suggests they are generated in cloud tops
reaching the tropopause and above. Here we explore their occurrence in
two convection environments of the same storm: one is developing with
clouds reaching above the tropopause, and one is collapsing with lower
clouds. We focus on those that form a distinct category with fast
risetimes below 20 µs, signifying they are at the very top of the
clouds. The discharges are observed in both environments. In the
collapsing cells they are related to substructures of convection. The
observations suggest that a range of storm environments may generate
corona discharges, and that they may be quite common in convective
surges.