Simultaneous radar and lidar cloud measurements at Geesthacht (53.5 degrees N, 10.5 degrees E)

Comparisons have been made of the cloud profiles obtained from the backscat ter signals of a 95-GHz radar and a 720-nm lidar system between 23 May and 4 November 1997 at Geesthacht (53 degrees 24' N, 10 degrees 26' E). Althoug h the wavelengths of the two systems differ by a factor of 4 000, remarkabl y similar data have been obtained in many cases. There are differences, tho ugh. Small droplets do not interact significantly with the radar pulses, an d hence can only be seen by the lidar due to their strong scattering in the UV/VIS. On the other hand, attenuation of the lidar pulses by underlying c louds and gas absorbers makes upper cloud regions and especially cloud top heights better detectable for the radar. Rain and snow falling out of a clo ud and evaporating on the way down cannot be distinguished from the cloud r egion by the radar, but a fast downward component in the Doppler spectrum i s indicative of precipitation in or under a cloud. For quantitative cloud s tudies collocated radar-lidar systems considerably add to the experimental capabilities of each of the two systems alone. (C) 1999 Elsevier Science Lt d. All rights reserved.