Lidar network observations of cirrus morphological and scattering properties during the International Cirrus Experiment 1989: the 18 October 1989 case study and statistical analysis

Abstract

Four lidars, located roughly 75 km from each other in the inner German Bight of the North Sea, were used to measure geometrical and optical properties of cirrus clouds. A complete cirrus life cycle was observed simultaneously with three lidars during a case study on 18 October 1989. Time series of particle backscatter, depolarization-ratio height profiles, cloud depths, optical thickness, and of the cirrus extinction-to-backscatter, or lidar, ratio describe the evolution of the cloud system. Cirrus formation was found to start at the tropopause in most causes. Ice clouds, measured at high midlatitudes (around 54°N), were thin with mean optical and geometrical depths mainly below 0.4 and 2 km, respectively. A good correlation between mean cloud optical and geometrical thickness, and a weak decrease of the mean optical depths with temperature was observed. -from Authors