Radar echoes from lightning were observed at wavelengths of 5.5, 50, and 111 cm. The 50-cm and the 111-cm radars produced strong echoes from every flash that we saw passing through the beams of the radars. Echoes were particularly strong on the radar with the longest pulse. Echoes received on radars that transmitted pulses 200 ns long consisted of short components. Some flashes reflected only one echo, but usually there were many more, and as many as 30 separate components of echoes have been counted. No echoes were detected by the 3-cm radar set, presumably because its pulse repetition rate was too low. A very small number of flashes produced detectable echoes at 5.5 cm, although many flashes were seen passing through the beam of the radar. These echoes behaved in either of two ways. Occasionally we saw strong echoes that appeared singly and moved rapidly in range, and we ascribed these to the tips of underdense channels. Stationary echoes that extended in range to become multiple echoes similar to those we observed at VHF were seen at 5.5 cm also, and we supposed that they were reflected by many channel segments that happened to be overdense at 5.5 GHz. This paper supplies data relating to the mean values and to the dispersion of radar cross-sectional areas of lightning channels viewed by VHF radar. |