Clouds and radiation: intensive observational campaign in the Netherlands (CLARA)

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To understand and model the radiative transport in a cloudy atmosphere, information on the cloud structure, optical properties and microphysics is indispensable. In order to obtain a detailed data set, four national institutes joined their efforts in the CLARA project. In the cause of the project the total number of participating institutes increased to ten. In total three experimental campaigns took place in the Netherlands in 1996. An extensive set of instrumentation was employed, including lidars, radar, infrared radiometers, microwave radiometer and radiosondes. Furthermore, in-situ aircraft measurements were carried out to measure the cloud droplet size distribution and the liquid water content. The data set is now available on CD-ROM. A platform independent JAVA interface allows the visualisation of most of the high resolution data. Extensive analysis of the observations has taken place. Research topics are:- Validation of satellite retrieval algorithms, - Lidar observations of cloud (optical) parameters, - Micro-physical properties of Sc clouds to estimate the indirect aerosol effect, - Cloud radar research, - Development and validation of sensor synergy algorithms, - Evaluation of cloud parameterizations in atmospheric models. An overview of the research performed within the CLARA project is presented in this final report. Much of the research will continue for the next few years. An important benefit of CLARA is that it was successful in organising a good scientific co-operation between the different research groups. In this way a national cloud remote sensing community was developed. This community is still growing.