Meteorological characterisation of the FEBUKO hill cap cloud experiments, Part II: Tracer experiments and flow characterisation with nested non-hydrostatic atmospheric models

The mesoscale and local flow conditions during the ground-based cloud passage experiment FEBUKO performed at the Schmücke Mountain (Thüringer Wald) during October 2001 and 2002 are investigated and discussed. Several methods are applied to characterise and classify the cloud episodes in terms of the flow conditions and their consistency to the philosophy of cloud passage experiments. For this the flow over the mountain range and a flow that connects the experimental sites are of crucial importance. The resulting selection of events is based on a synoptical evaluation (Part I of the work) and provides a recommendation of events, which are adequate for subsequent investigations. The mesoscale air flow over the complex terrain is characterised by means of non-dimensional flow parameters like Froude number and the non-hydrostatic meteorological model LM. An analysis of the locally measured natural tracer ozone is intended to assure that measurements were performed in identical air masses at the different locations during the 14 cloud events. It is found that the flow connecting the measurement sites is distinctly associated with the flow over and/or around the Thüringer Wald, which in turn is determined by the synoptical flow and the thermal stratification. Furthermore, applications of tracer techniques using the inert SF 6 for studies of transport processes in the experimental site and verification of the location of measurement stations are presented. For the tracer experiments in October 2001 and 2002 an attempt is made to reproduce them with an anelastic non-hydrostatic model in conservation form in order to understand the tracer dispersion.