Within the framework of the international field campaign COPS (Convective and Orographically-induced Precipitation Study), a large suite of state-of-the-art meteorological instrumentation was operated, partially combined for the first time. This includes networks of in situ and remote-sensing systems such as the Global Positioning System as well as a synergy of multi-wavelength passive and active remote-sensing instruments such as advanced radar and lidar systems. The COPS field phase was performed from 01 June to 31 August 2007 in a low-mountain area in southwestern Germany/eastern France covering the Vosges mountains, the Rhine valley and the Black Forest mountains. The collected data set covers the entire evolution of convective precipitation events in complex terrain from their initiation, to their development and mature phase until their decay. Eighteen Intensive Observation Periods with 37 operation days and eight additional Special Observation Periods were performed, providing a comprehensive data set covering different forcing conditions. In this article, an overview of the COPS scientific strategy, the field phase, and its first accomplishments is given. Highlights of the campaign are illustrated with several measurement examples. It is demonstrated that COPS research provides new insight into key processes leading to convection initiation and to the modification of precipitation by orography, in the improvement of quantitative precipitation forecasting by the assimilation of new observations, and in the performance of ensembles of convection-permitting models in complex terrain.

[1] On 4 days in summer and winter the mixing layer height over the municipal area of Munich, Germany, was determined by several remote sensing instruments and in situ probes. The main motivation was to obtain information on aerosols, and therefore we decided to understand the mixing layer as that layer where most of the locally produced aerosols are concentrated. In this paper we wanted to investigate the potential of the quite different methodologies which depend on measurements of aerosol properties and those which do not. The operation of two lidars, a ceilometer, a wind-temperatureradar, a sodar, radiosondes, and aerosol probes onboard of a microlight aircraft allowed such a thorough intercomparison. As the instruments were located at different sites, the horizontal homogeneity of the mixing layer could also be observed. It was found that the agreement between the different methodologies is very good as long as the mixing layer height does not exceed approximately 1 km, which is the common measurement range of all instruments. In summer, however, the mixing layer can reach 2 km and more, so that the lidar turns out to be the most capable remote sensing technique. Another advantage of the lidar is the possibility to clearly derive the internal structure of the mixing layer. The latter is important in cases when simple parameterizations assume vertical homogeneity of aerosol properties within the mixing layer. On the other hand, lidars are quite expensive and require a trained operator. As a conclusion, the development of unattended working lidars including automated data evaluation should be fostered. From the limited data set it was found that the mixing layer height in Munich did not change more than approximately 100 m over a horizontal distance of around 50 km. If this finding can be confirmed by further measurements, the area of Munich is a good test bed for the validation of aerosol retrievals from satellite data with medium spatial resolution and for the validation of the numerical treatment of aerosols in mesoscale chemistry transport models.

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This paper summarizes the findings of seven years of research on föhn conducted within the project 'Föhn in the Rhine Valley during MAP' (FORM) of the Mesoscale Alpine Programme (MAP). It starts with a brief historical review of föhn research in the Alps, reaching back to the middle of the 19th century. Afterwards, it provides an overview of the experimental and numerical challenges identified before the MAP field experiment and summarizes the key findings made during MAP in observation, simulation and theory. We specifically address the role of the upstream and cross-Alpine flow structure on föhn at a local scale and the processes driving föhn propagation in the Rhine Valley. The crucial importance of interactions between the föhn and cold-air pools frequently filling the lower Rhine Valley is highlighted. In addition, the dynamics of a low-level flow splitting occurring at a valley bifurcation between the Rhine Valley and the Seez Valley are examined. The advances in numerical modelling and forecasting of föhn events in the Rhine Valley are also underlined. Finally, we discuss the main differences between föhn dynamics in the Rhine Valley area and in the Wipp/Inn Valley region and point out some open research questions needing further investigation.

SUMMARYThis paper examines the impact of a mesoscale analysis (2.5 km grid distance) on the simulation of the mesogamma scale aspects of föhn in the Rhine Valley. The föhn event, documented during IOP15 (5 November 1999) of the Mesoscale Alpine Programme, was standard in terms of intensity and was characterized by an important temporal variability. Many instruments operating in the Rhine valley target area are used to validate the simulation, in particular the airborne nadir-pointing lidar LEANDRE 2 (flown over the lower Rhine valley) as well as a wind profiler and a radio accoustic sounding system collocated in Rankweil, Austria. The large observational dataset acquired during the IOP allowed documentation of the entire föhn life cycle. For most of the IOP, a cold pool remained near the ground in the lower northern part of the valley. The non-hydrostatic model Meso-NH, used in a grid-nesting configuration with two nested models and initialized with a mesoscale analysis, allowed us to simulate realistically the location and depth of the cold pool. The relationship between the föhn intensity and the large-scale environment is also examined. The flow regime is a 'flow around' the Alps. The variability of this flow at the western tip of the Alps could explain some of the temporal changes observed at low level in the Rhine valley.