Meteorological characterisation of the FEBUKO hill cap cloud experiments, Part I: Synoptic characterisation of measurement periods

The synoptic and local meteorological conditions during the ground-based cloud passage experiment FEBUKO performed at the Schmücke Mountain (Thüringer Wald) during October 2001 and 2002 are reviewed and discussed. A general description of the weather types and a classification of air masses are presented. In the second part the meteorological situations are illustrated in detail for the different experimental cloud events. The main objective of this two-part study is to classify the cloud events with respect to the occurring weather conditions and consistency to the philosophy of cloud passage experiments. Therefore, particular emphasis is placed on the incident flow conditions and on the separation of orographic and non-orographic cloud types. In the case of the flow characterisation, weather charts and calculated backward trajectories are used to determine the horizontal wind pattern and the rawinsonde data for the vertical structure of wind vectors. Additionally, in order to describe the local flow conditions the observed wind speed and direction at the experimental site on the summit are applied for the total of 14 cloud episodes. For the examination of the orographic character and properties of clouds, satellite pictures of different spectral channels, vertical thermodynamic data of the rawinsonde as well as the measured liquid water content and the cloud base height are evaluated. The resulting event evaluation provides a basis for subsequent local analysis of the flow over and/or around the mountain range (Part II of the study). Generally, it is found that more suitable conditions were encountered in October 2001 than in October 2002. Especially for the anticyclonic southwest weather-type, stable incoming flow condition as well as orographically induced clouds could be clearly identified.