Cloud observations and modeling within the European BALTEX Cloud Liquid Water Network

A prototype of a European cloud observation network was established as part of the EU-project CLIWA-NET during three campaigns. The first CLIWA-NET network campaign (CNN I) took place in August/September 2000 and first results are presented in this work. Cloud properties, with a focus on liquid water path (LWP), were derived at 11 stations within the BALTEX modeling area from passive microwave radiometer, lidar ceilometer and infrared radiometer measurements. In an indirect evaluation of LWP accuracy performed during cloud free scenes, clear-sky biases in LWP ranging between –15 and +6 g m–2 were identified, which are well within the theoretical accuracy of the retrievals. For the Lindenberg station the retrievals were compared with forecasts from four atmospheric models. After restricting the model predictions to non-precipitating cases, which are the only cases for which retrieved LWPs are accurate, reasonable agreement was found between the observations and three of the models.