The field experiment DAMOCLES 2007 (Hamburg Arctic Ocean Buoy Drift Experiment DAMOCLES 2007-2008) consisted of the deployment and tracking of an array of 16 drifting autonomous buoys in the Central Arctic Ocean. The buoys were deployed in a quadratic array with 400 kilometres side length in the Siberian sector of the Central Arctic Ocean in April 2007. While drifting towards Fram Strait the buoys delivered at approximately 1-hourly time intervalls position, sea level pressure and temperature for several months with the last buoy transmitting until January 2008. The aim of the experiment was to study the Atmosphere-Ice-Ocean interaction, especially the impact of cyclones on the formation and transport of sea ice. DAMOCLES 2007 and DAMOCLES 2008 are a contribution to European integrated project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies) which is funded by the European Union. DAMOCLES is a contribution to IPY 2007-2008 (International Polar Year).

The drift buoys experiment FRAMZY 2007 consisted of the deployment and tracking of an array of 29 drifting autonomous buoys (16 ice, 13 water) in the Fram Strait region. The buoys were deployed in March 2007 and sampled data until end of April 2007. The aim of the experiment was to study the Atmosphere-Ocean interaction and the Atmosphere-Ice-Ocean interaction, especially the impact of cyclones on the energy budget of sea ice and ocean surface. FRAMZY 2007 was the third one in a series of five field experiments (1999,2002,2008,2009) carried out in the frame of the Collaborative Research Centre 512 (Cyclones and the North Atlantic Climate System) funded by the German Science Foundation.

The field experiment DAMOCLES 2008 (Hamburg Arctic Ocean Buoy Drift Experiment DAMOCLES 2008-2009) consisted of the deployment and tracking of 9 drifting autonomous ice buoys in the Arctic Ocean. Seven buoys were deployed in the Canadian sector of the Arctic Ocean in late April 2008. Two more buoys were deployed in the Beaufort Sea and in the Laptev Sea in September and October 2008. The platforms report position, atmospheric pressure, temperature and humidity, wind speed and ice temperature at 3-hourly time steps. The last two buoys additionally report wind direction. The aim of the experiment was to study the Atmosphere-Ice-Ocean interaction, especially the impact of cyclones on the formation and transport of sea ice. DAMOCLES 2008 and its predecessor DAMOCLES 2007 are a contribution to European integrated project DAMOCLES (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies) which is funded by the European Union. DAMOCLES is a contribution to IPY 2007-2008 (International Polar Year).

The Fram Strait Cyclone Experiment, FRAMZY 1999, took place in the Fram Strait and Greenland Sea region during April 1999. Using aircraft, ice buoys, ship and satellite measurements a data set was compiled to investigate the properties of Fram Strait cyclones, their cyclogenetic conditions on the large- and meso-scale, and their local effects on sea ice drift and sea ice distribution and, thus, on the freshwater flow through the Fram Strait. The data were used for validation of cyclone simulations with coupled mesoscale models of the atmosphere-ice-ocean system. FRAMZY 1999 was the first one in a series of five field experiments (2002,2007,2008,2009) carried out in the frame of the Collaborative Research Centre 512 (Cyclones and the North Atlantic Climate System) funded by the German Science Foundation. 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 Valdivia

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 FRAMZY 2008 experiment aimed at the measurement of the sea ice drift in the Fram Strait and its relation to the atmospheric forcing, primarily to that by cyclones. FRAMZY 2008 was the fourth experiment with this objective and followed the FRAMZY experiments in 1999, 2002 and 2007. On 20 January 2008, seven CALIB (Compact Air-Launch Ice Buoys) buoys were deployed from a transport aircraft in a regular array of 200 km by 100 km size centered at 82.6¿N, 1.0¿E in the northern part of Fram Strait. Buoys measured autonomously air pressure, temperature and position at approximately one-hourly intervals and transmitted the data via the Argos satellite system. The lifetime of the buoys before they were lost at the ice edge or due to the breaking of ice was between 7 and 39 days (final date 28 February 2008). The southernmost position reached by a buoy after 39 days was 76.2¿N, -12.0¿E, corresponding to an average drift speed of 16.9 km per day or 0.20 ms-1. During the FRAMZY 2008 period eight cyclones passed through Fram Strait. The paper presents details of the ice motion and the atmospheric conditions. In the appendix 12-hourly maps of sea-level pressure and surface air temperature as analysed by the ECMWF, daily maps of ice concentration and daily NOAA satellite images are presented.

From 26 March to 22 April 2003, Germany and Finland carried out a joint expedition (ABSIS - Arctic Atmospheric Boundary Layer and Sea Ice Interaction Study) to test and improve the description of the ocean-ice-atmosphere interaction processes. ABSIS was part of the German ACSYS (Arctic Climate System Study) contribution supported by the Ministry of Education and Research and was connected with the RV Polarstern Winter Arctic Polynia Study expedition. The main objectives of ABSIS were to collect data sets to quantify and study: (a) the thermodynamic and dynamic interaction processes at the ice-atmosphere interface and (b) the vertical structure of the atmospheric boundary layer, particularly the Arctic inversion. The latter is a nearly permanent feature over the sea ice. The Arctic inversion is particularly low and strong in winter and effects the exchange between the boundary layer and the free atmosphere as well as the interaction processes at the ice surface. To achieve the above-mentioned objectives various platforms were applied and placed within a 200 km2 area north of Spitsbergen during the expedition period 26 March to 22 April 2003: RV Polarstern and RV Aranda, a research aircraft (Falcon-20 of the German Aerospace Center), 11 automatic ice buoys, and one ice camp station close to RV Polarstern (8-18 April 2003 only). 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 Aranda, ground data at RV Polarstern, ice station near RV Polarstern

The field campaign LOFZY 2005 (LOFoten ZYklonen, engl.: Cyclones) was carried out in the frame of Collaborative Research Centre 512, which deals with low-pressure systems (cyclones) and the climate system of the North Atlantic. Cyclones are of special interest due to their influence on the interaction between atmosphere and ocean. Cyclone activity in the northern part of the Atlantic Ocean is notably high and is of particular importance for the entire Atlantic Ocean. An area of maximum precipitation exists in front of the Norwegian Lofoten islands. One aim of the LOFZY field campaign was to clarify the role cyclones play in the interaction of ocean and atmosphere. In order to obtain a comprehensive dataset of cyclone activity and ocean-atmosphere interaction a field experiment was carried out in the Lofoten region during March and April 2005. Employed platforms were the Irish research vessel RV Celtic Explorer which conducted a meteorological (radiosondes, standard parameters, observations) and an oceanographic (CTD) program. The German research aircraft Falcon accomplished eight flight missions (between 4-21 March) to observe synoptic conditions with high spatial and temporal resolution. In addition 23 autonomous marine buoys were deployed in advance of the campaign in the observed area to measure drift, air-temperature and -pressure and water-temperature. 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 Celtic Explorer

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.

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.