Positive Flash High-Speed Spectral Characteristics in the Upward Lightning Triggering Study (UPLIGHTS)

The spectral properties of positive lightning flashes have been recorded for the first time. Two high-speed cameras, each operating at 35,000 fps, have recorded the positive leaders in the UPLIGHTS experiment in Rapid City, South Dakota. One of the cameras is modified to a spectrograph with a transmission diffraction grating to capture the lightning emissions from 400 to 900 nm. The positive leader infrared spectral emissions are relatively more intense compared to the visible spectral emissions. The positive lightning return stroke peak currents range from 24 to 91 kA.