Particularly Bright Lightning Pulses

Frame-by-frame LIS measurements show that typical lightning flashes are dominated by dim pulses (called "groups"). Only a few groups stand out as exceptional in a given flash. We use these bright groups to define an optical multiplicity that measures how often a given flash lights up the thundercloud far beyond the radiance of a typical cloud pulse. The optical multiplicity is advanced by a combination of strokes and K-changes.

Satellite lightning imagers record lightning flashes at 500 frames per second. We use the Lightning Imaging Sensor (LIS) on the Tropical Rainfall Measuring Mission (TRMM) satellite to describe the time‐evolution of lightning from first light through the end of the flash. The radiant energy of the flash may appear as isolated flickers, or it may occur as a stream of nearly continuous illumination coming out of the top of the cloud. We organize these sustained optical pulses into features called "series" and examine their energy and timing in the flash. Flashes and series are comprised of mostly dim optical emissions, but a small number of pulses substantially increase the energy of the flash. These bright "groups" and the "bright series" that contain them describe physical lightning processes that produce large amounts of light. The frequency of bright series and the amount of time between subsequent bright series agree with ground‐based measurements of return strokes and physical processes known as K‐changes. Thus, lightning imagers may observe a combination of physical lightning processes.