Optical Observations of Lightning from a High-Altitude Airplane
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Abstract Lightning has been observed from above cloud top by using satellites, balloons, rockets, and high-altitude airplanes, each of which provides a unique perspective and holds the potential for gaining new understanding of lightning phenomena. During the 1980s extensive optical observations of lightning have been made from a NASA U-2 airplane with a goal toward placing a lightning sensor in geostationary orbit. Analysis of these U-2 measurements suggest that most of the light generated within a cloud escapes, and that the optical energy of lightning measured from above clouds is not significantly different than the measurements made from below of discharges to ground. Near-infrared optical measurements were made of nearly 1300 optical pulses produced by 79 lightning flashes. The median source estimate of peak flash radiance is approximately 108 W with a dynamic range of less than three orders of magnitude. Of these 79 flashes, 90 percent produced peak radiant energy densities of 4.7 μJ m−2 sr−1 or gr...