Lidar detected spike returns

Abstract

Lidar measurements of spike returns from clear air are presented. These spikes occur infrequently (approximately one in hundred returns) but provide returns that are significantly stronger (occasionally an order of magnitude larger) than the average aerosol backscatter signal. The spike density is 5.7e-3 spikes m-3 for backscattering cross sections estimates to be between 0.003 and 0.080 mm2 sr-1. A modified form of the lidar equation which includes returns from large particulates is presented and the probability distribution for the spike magnitudes is derived from five million measurements.