A Comparison of the Optical Pulse Characteristics of Intracloud and Cloud-to-Ground Lightning as Observed above Clouds.

Abstract The time-resolved optical waveforms at 777.4 nm and electric-field changes produced by intracloud and cloud-to-ground lightning flashes were measured above clouds from a U2 airplane (flying at a height of 20 km) at the same time that ground-based measurements of lightning were obtained from a mobile laboratory and a regional lightning location network. The U2 optical pulse trains are examined for variability both within and between flashes. The optical pulse characteristics of cloud-to-ground flashes are further subdivided into first strokes, subsequent strokes, and intracloud components (k-changes). Descriptive statistics on these pulse categories have been compiled for 25 visually confirmed cloud-to-ground flashes (229 optical pulses) and 232 intracloud flashes (3126 optical pulses). The pulse shapes and intensities of intracloud and cloud-to-ground flashes as viewed from above cloud are shown to exhibit remarkably similar waveshapes, radiances, and radiant energy densities. The median radiance...