ECLIPS and related observations - what we have learned and prospects for future observations

The Experimental Cloud Lidar Pilot Study (ECLIPS) was carried out to assess what useful information on clouds related to climate studies could be gleaned. This small-scale venture showed indeed that useful climate - related information on cloud base height, cloud top, where possible, and visible optical depth could be obtained. The addition of infrared radiometry could provide similar data on IR emittance and optical depth. The methods were mainly applicable to the climatically - important cirrus clouds, but useful data were also retrieved on other cloud types. Some of these data will be presented, including some from a continuing long - term cirrus data set. Since ECLIPS, other large initiatives such as ARM have been developed, and produce ECLIPS - type observations on a long - term basis in crucial climate regions of the world. With the advent of modern, low - energy, micro - pulse lidars, cloud observations on a long-term, unattended basis have become much more feasible. This has in fact led to an expansion of lidar ground based observations around the world. The possibility of a formal global network of lidar observations is discussed. The various degrees of sophistication required for the more extensive climatic data, such as IR optical depth (LIRAD method) and even cloud particle size (lidar/radar/radiometer methods) are treated. However, even lidar observations on their own give valuable data.