KONTROL 1985 is part of research activities focused on organized convection phenomena as they are often manifested in organized cloud patterns like the well-known boundary layer cloud streets or open and closed cellular cloud structures. The experimental part of the investigations began with the experiment KonTur (Konvektion and Turbulenz) in September and October 1981. It continued with the experiments KONTROL in August 1984 and KONTROL in October 1985. All experiments took place over the German Bight in the southeastern part of the North Sea. The experimental concept based on the use of three fixed stations performing continuous aerological and surface observations and two aircraft conducting detailed observations during special periods. The stations were the island of Heligoland, the research vessel Valdivia and the research platform NORDSEE (54°42'N, 7°10'E). The aircraft were a FALCON-20 of DFVLR and a DO-28 Skyservant of the TU Braunschweig.

KONTROL 1984 is part of research activities focused on organized convection phenomena as they are often manifested in organized cloud patterns like the well-known boundary layer cloud streets or open and closed cellular cloud structures. The experimental part of the investigations began with the experiment KonTur (Konvektion and Turbulenz) in September and October 1981. It continued with the experiments KONTROL in August 1984 and KONTROL in October 1985. All experiments took place over the German Bight in the southeastern part of the North Sea. The experimental concept based on the use of two fixed stations performing continuous aerological and surface observations and two aircraft conducting detailed observations during special periods. The stations were the research vessel Valdivia and the research platform NORDSEE (54°42'N, 7°10'E). The aircraft were a FALCON-20 of DFVLR and a DO-28 Skyservant of the TU Braunschweig.

The field experiments ALKOR 2000 (consisting of three cruises: ALKOR 4/2000, 6/2000, 10/2000) and ALKOR 2001 (4/2001, 6/2001, 10/2001) took place in the central Baltic Sea. The six cruises of the German Research Vessel Alkor with duration of about seven days each led to a point of the Baltic Sea which is most remote from the adjacent lands and additionally a grid point of regional climate model REMO. The ALKOR experiments as well as BASIS 1998 and BASIS 2001 are part of the research compound BALTIMOS (BALTic sea Integrated MOdel System). BALTIMOS in turn is part of the Baltic Sea Experiment (BALTEX). The overall objective of all eight field experiments (ALKOR and BASIS) was to collect a comprehensive data set suited to validate the coupled model system BALTIMOS for the Baltic Sea region. The observations mainly focus on: - the atmospheric boundary layer structure and processes and the air-sea-ice interaction over areas with inhomogeneous sea ice cover - the atmospheric boundary layer structure over open water under different synoptic conditions such as cold-air advection, warm-air advection or frontal passages. In addition to the published datasets several other measurements were performed during the experiment. Corresonding datasets will be published in the near future and are available on request. Details about all used platforms and sensors and all performed measurements are listed in the fieldreport. The following datasets are available on request: ground data at RV Alkor

The field experiment FRONTEX 1989 (FRONT EXperiment) took place in the German coastal area of the North Sea between 2 May and 6 June 1989. It was coordinated by the Meteorological Institute of the University of Hamburg and was primarily funded by the German Research Foundation (DFG) in the frame of the priority programme "Fronten und Orographie". The scientific aim was the investigation of cold fronts moving in from the North Sea and reaching the coastal area. The different physical properties of sea and land surface (roughness, humidity, temperature, heat conduction and heat capacity) modify the frontal structure at landfall. The modification should first alter the boundary layer and is then communicated to higher levels, thus effects like convection and convergence will be found farther inland. The experimental concept was to monitor the passing front on all relevant temporal and spatial scales. To obtain this goal a large variety of measurement platforms was employed. Ground based remote sensing and in-situ measurements were performed at Heligoland, Schleswig, Hanover, Emden, Berlin, and on board the research vessel. Three research aircraft (POLAR-2 and POLAR-4 of AWI Bremerhaven and DO-128 of TU Braunschweig) were used to measure the frontal structure with high temporal and spatial resolution.

The Convection and Turbulence Experiment (KonTur) was conducted in the southeastern part of the North Sea from 14 September to 21 October 1981 (with a break from 4 to 8 October). KONTUR aimed at two main scientific objectives. First, to observe the formation and time variation of regularly organized convection in the lower troposphere as a function of the mean atmospheric flow and the lower boundary condition and to quantify the dependence of the vertical transports of momentum, heat and water mass on various scales of motion in order to test existing convection models and to provide an observational background for the extension of theoretical concepts. Second goal was to determine the mean and turbulent quantities within the marine atmospheric boundary layer (ABL), including the large scale horizontal and vertical advection of momentum, heat and water vapour, cloud microphysics and the radiation field, in order to assemble a comprehensive data set for boundary layer modelling with first and second order closure methods. The experiment covered an area in the southeastern part of the North Sea (German Bight), roughly between latitudes 53¿N and 56¿N and longitudes 6¿E and 9¿E. Both the convection and the turbulence programme made use of the same experimental tools which can be subdivided in the following four groups: the central station occupied by the research vessel Meteor, the aerological network (Borkumriff, RV Meteor, RV Gauss/Poseidon, Research Platform Nordsee, Elbe 1), two aircraft (Hercules C-130, Falcon 20) and supporting observations, such as satellite images, cloud photography, surface and upper air large-scale fields from routine data. KONTUR 1981 was followed by the experiments KONTROL 1984 and KONTROL 1985.

The field experiments ALKOR 2000 (consisting of three cruises: ALKOR 4/2000, 6/2000, 10/2000) and ALKOR 2001 (4/2001, 6/2001, 10/2001) took place in the central Baltic Sea. The six cruises of the German Research Vessel Alkor with duration of about seven days each led to a point of the Baltic Sea which is most remote from the adjacent lands and additionally a grid point of regional climate model REMO. The ALKOR experiments as well as BASIS 1998 and BASIS 2001 are part of the research compound BALTIMOS (BALTic sea Integrated MOdel System). BALTIMOS in turn is part of the Baltic Sea Experiment (BALTEX). The overall objective of all eight field experiments (ALKOR and BASIS) was to collect a comprehensive data set suited to validate the coupled model system BALTIMOS for the Baltic Sea region. The observations mainly focus on: - the atmospheric boundary layer structure and processes and the air-sea-ice interaction over areas with inhomogeneous sea ice cover - the atmospheric boundary layer structure over open water under different synoptic conditions such as cold-air advection, warm-air advection or frontal passages. In addition to the published datasets several other measurements were performed during the experiment. Corresonding datasets will be published in the near future and are available on request. Details about all used platforms and sensors and all performed measurements are listed in the fieldreport. The following datasets are available on request: ground data at RV Alkor

The field experiment ARKTIS 1993 was the third one in a series of experiments in the Arctic region performed by a group of climate researchers from Hamburg. The campaign took place in the Greenland Sea west of Spitsbergen from 1 to 25 March 1993. The preceding experiments were ARKTIS 1988 (5 - 25 May 1988) in the same geographic region and ARKTIS 1991 (20 February - 13 March 1991) located between North Norway and Bear Island. The main objective of ARKTIS 1993 was the investigation of cold air outbreaks from the Arctic sea ice onto the open water, in this case the West Spitsbergen current. To get a concise picture of all stages of boundary layer modification in cold air outbreaks a wide variety of measurement platforms was employed. Three reseach vessels (Polarstern, Valdivia, Prof. Multanovsky) operated in the experimental area providing surface observations and radiosonde data. Aerological data was also collected at three land stations (Bear Island, Danmarkshavn, Ny Alesund) which intensified their operational radiosonde program. Most essential measurement were taken by the research aircraft Falcon and DO-128 which took profiles and cross sections within the air flow. Eleven flight missions were performed.

The field experiment BASIS 1998 took place in the Gulf of Bothnia in the Baltic Sea in a boundary zone between the open sea and the ice-covered sea from 16 February to 7 March, 1998. BASIS 1998 as well as the field experiments BASIS 2001 and ALKOR 2000 and 2001 are part of the research compound BALTIMOS (BALTic sea Integrated MOdel System). BALTIMOS in turn is part of the Baltic Sea Experiment (BALTEX). The overall objective of all eight field experiments (ALKOR and BASIS) was to collect a comprehensive data set suited to validate the coupled model system BALTIMOS for the Baltic Sea region. The observations mainly focus on: - the atmospheric boundary layer structure and processes and the air-sea-ice interaction over areas with inhomogeneous sea ice cover - the atmospheric boundary layer structure over open water under different synoptic conditions such as cold-air advection, warm-air advection or frontal passages. Observations during BASIS 2001 were made at three land stations and the Finnish research vessel Aranda. All stations performed radiosonde measurements. The German research aircraft Falcon had six flight missions with measurements of meteorological parameters and turbulent fluxes. In addition to the published datasets several other measurements were performed during the experiment. Corresonding datasets will be published in the near future and are available on request. Details about all used platforms and sensors and all performed measurements are listed in the fieldreport. The following datasets are available on request: meteorological stations Kokkola, Umea, Merikarvia, ground data at RV Aranda

The expedition ARKTIS 1988 was initiated and directed by the Collaborative Research Centre 318 of the German Research Foundation entitled "Climatically relevant proceses in the system ocean-atmosphere-ice" and established at the University of Hamburg. The field experiment took place in the Fram Strait in the area straddling the ice margin west of Spitsbergen during the period from 4 to 26 May 1988. The experimental concept for the investigation of boundary layer modification and certain cloud structures in cases of off-ice and on-ice air flows was to maneuver one ship, the research icebreaker POLARSTERN, about 100 km into the ice and to operate with a second ship, the research vessel VALDIVIA, in the open water near the ice edge. Several aircraft operating from the airport at Longyearbyen on Spitsbergen were intended to measure the mean structures, variances and covariances at different distances from the ice edge. ARKTIS 1988 was followed by the two experiments ARKTIS 1991 and ARKTIS 1993.

The field experiment ARKTIS 1991 was an expedition planned by meteorologists of the Collaborative Research Centre 318 entitled "Climatically relevant processes in the system ocean-atmosphere-ice" which is funded by the German Research Foundation and established at the University of Hamburg. The expedition took place in the Norwegian Sea between Northern Norway, Bear Island and Jan Mayen during the period 17 February until 15 March 1991. The main aim of the experiment was the investigation of cold air outbreaks from the surrounding Arctic ice sheets. During such weather episodes the air mass coming from the ice is rapidly modified over the water due to the contrasts in temperature, heat conduction, humidity and roughness between ice and water. This leads to the formation of a "new" boundary layer. Its depth, mean temperature and moisture increases with increasing distance from the ice edge mainly due to sensible and latent heat supply from the ocean. The investigations of cold air outbreaks and Arctic stratus by scientists of the Collaborative Research Centre 318 began already three years before with the field experiment ARKTIS 1988 which took place in the area west of Spitsbergen in May 1988. ARKTIS 1991 is a continuation of this work under winterly weather conditions. ARKTIS 1991 was followed by the experiment ARKTIS 1993. As in ARKTIS 1988 the research vessel Valdivia and the two research aircraft FALCON-20 of the DLR at Oberpfaffenhofen and DO-128 of the TU Braunschweig were at our disposal. Radiosonde measurements were performed on board of RV Valdivia and on Bear Island.