Das Projekt "Untersuchung von Wolken mit boden- und luftgestuetztem Radar und Lidar (CARL)" wird vom Umweltbundesamt gefördert und von GKSS-Forschungszentrum Geesthacht, Institut für Atmosphärenphysik durchgeführt. To validate and to improve cloud parameterizations in general circulation models, a detailed information about the cloud characteristics must be available on large scales. Crucial cloud characteristics to the cloud radiation budget, eg the particle size distribution (liquid or ice, as represented by the effective radius re), and liquid or ice water content (phase and W) are presently poorly measured at such a scale. New measurements must be carried out from airborne and spaceborne platforms to allow cloud sampling on large horizontal scales. It is the objective of this work tor prepare such developments by testing new observational remote sensing methods combining lidar and radar systems. In order to assess the retrieval performance, two phases are proposed which are two important steps in the development towards new systems in Europe. In the two phases the methodology will be tested for both warm and cold clouds. In a first phase a ground-based experiment will be conducted using two lidar systems operated at 0,53/1,06 and 10,6 micrometer and a 95 GHz radar. In-situ measurements will be used as a validation and reference information. In a second phase airborne measurements will be taken using lidar and radar instruments referenced to ground-based and in-situ observations. In both phases, model calculations will allow to analyze the impact of the cloud parameter retrieval and related errors, on the radiation and dynamics at the meso-scale. They will also be used to provide a feedback on the experimentation (quantity and quality of parameters, representativeness, parametrizations, ...). Prime Contractor: Centre National de la Recherche Scientifique, FU 0005, Institut Pierre-Smone Laplace; Guyancourt/France.