Absolute Spectral Irradiance Measurements of Lightning from 375 to 880 nm

Abstract A spectrometer-detector optical multichannel analyzer system capable of absolute spectral irradiance measurements has been used to record the time-integrated emissions (150 or 300 ms) from cloud-to-ground lightning. Two detectors, one operating in the 375–695 nm region and one in the 650–880 nm region, recorded emissions from the same lightning. Ten flashes containing 46 recorded strokes were selected for detailed analysis from 500 flashes recorded in 1981. Thew ten flashes occurred within three degrees of the optical axis of the spectrometer system. The average stroke spectral irradiance from 375 to 650 nm for flashes at approximately 15 km is 3.5 × 10−5 J m−2 per stroke with a standard deviation of 2.0 × 10−5 and a range from 0.7 × 10−5 to 6.8 × 10−5 J m−2 per stroke. The average stroke spectral irradiance from 650 to 880 nm for the same strokes is 1.2 × 10−5 j m−2 per stroke with a standard deviation of 0.7 × 10−5 and a range from 0.5 × 10−5 to 3.2 × 10−5 J m−2 per stroke. The ratio of the vis...