The field experiment ACSYS 1998 took place in the Greenland Sea west of Spitsbergen from 10 to 25 March 1998. It was planned and organized by scientists of the Meteorological Institute of the University of Hamburg within the national research project ACSYS (Arctic Climate System Study) which was funded by the German Bundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie (BMBF). The national ACSYS project is part of the international ACSYS research program which is a sub-program of the World Climate Research Program (WCRP). The objective of the ACSYS 1989 field experiment was the investigation of the atmospheric boundary layer in case of on-ice air flow in wintertime. Cyclones, reaching the Arctic sea ice from the Greenland Sea or Barents Sea are the strongest synoptic-scale weather signals in the Arctic region. They transport warm, moist and cloudy air from the open water to the Arctic shield. Especially in wintertime when the temperature contrast between the ocean and the ice surface is large the effects in the boundary layer over the ice are also significant. The research aircraft Falcon performed six flight missions from 11 to 21 March measuring meteorological parameters and turbulent fluxes.

The field experiment ACSYS 1998 took place in the Greenland Sea west of Spitsbergen from 10 to 25 March 1998. It was planned and organized by scientists of the Meteorological Institute of the University of Hamburg within the national research project ACSYS (Arctic Climate System Study) which was funded by the German Bundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie (BMBF). The national ACSYS project is part of the international ACSYS research program which is a sub-program of the World Climate Research Program (WCRP). The objective of the ACSYS 1989 field experiment was the investigation of the atmospheric boundary layer in case of on-ice air flow in wintertime. Cyclones, reaching the Arctic sea ice from the Greenland Sea or Barents Sea are the strongest synoptic-scale weather signals in the Arctic region. They transport warm, moist and cloudy air from the open water to the Arctic shield. Especially in wintertime when the temperature contrast between the ocean and the ice surface is large the effects in the boundary layer over the ice are also significant. The research aircraft Falcon performed six flight missions from 11 to 21 March measuring meteorological parameters and turbulent fluxes.

Products of liquid water path (LWP), rain water path (RWP) and integrated water vapor (IWV, also called precipitable water vapor (PWV)) are retrieved from microwave radiometer observations with auxiliary measurements from backscatter lidar and cloud radar. The nadir measurements were taken by the German High Altitude and Long range research aircraft (HALO) during the Next generation Advanced Remote sensing for VALidation campaign 2 (NARVAL2) in August 2016. Products are provided over tropical Atlantic east of Barbados. This experiment provides column integrated quantities as seen from satellite perspective but with higher spatially resolution (about 1 km footprint) than available from microwave satellites.

NARVAL-South: Measurements of microwave radiometer brightness temperatures, radar reflectivity and linear depolarisation ratio, and dropsonde atmospheric profiles from aircraft campaign over tropical Atlantic out of Barbados. Aim of the campaign was the observation of shallow convection in the trade wind region east of Barbados. website: https://mpimet.mpg.de/en/research/observations/research-aircraft-halo

Products of liquid water path (LWP), rain water path (RWP) and integrated water vapor (IWV, also called precipitable water vapor (PWV)) are retrieved from microwave radiometer observations with auxiliary measurements from backscatter lidar and cloud radar. The nadir measurements were taken by the German High Altitude and Long range research aircraft (HALO) during the Next generation Advanced Remote sensing for VALidation campaign South (NARVAL-South) in December 2013. Products are provided over tropical Atlantic east of Barbados. This experiment provides column integrated quantities as seen from satellite perspective but with higher spatially resolution (about 1 km footprint) than available from microwave satellites.

NARVAL2: Measurements of microwave radiometer brightness temperatures, radar reflectivity and linear depolarisation ratio, and dropsonde atmospheric profiles from aircraft campaign over tropical Atlantic out of Barbados. During this campaign, a broad range of states of convection were observed from suppressed and shallow convection in relatively dry surroundings to deep convection in the ITCZ. website: https://mpimet.mpg.de/en/research/observations/research-aircraft-halo

NAWDEX: Measurements of microwave radiometer brightness temperatures, radar reflectivity and linear depolarisation ratio, and dropsonde atmospheric profiles from aircraft campaign over mid-latitude Atlantic out of Iceland. The campaign explored the impact of diabatic processes on disturbances of the jet stream and their influence on downstream high-impact weather through the deployment of four research aircraft. Website: http://www.pa.op.dlr.de/nawdex/

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

NARVAL-North: Measurements of microwave radiometer brightness temperatures, radar reflectivity and linear depolarisation ratio, and dropsonde atmospheric profiles from aircraft campaign over mid-latitude Atlantic out of Iceland. Aim of the campaign was the observation of clouds associated with the cold sector of mid-latitude cyclones.

Products of liquid water path (LWP), rain water path (RWP) and integrated water vapor (IWV, also called precipitable water vapor (PWV)) are retrieved from microwave radiometer observations with auxiliary measurements from backscatter lidar and cloud radar. The nadir measurements were taken by the German High Altitude and Long range research aircraft (HALO) during the Next generation Advanced Remote sensing for VALidation campaign South (NARVAL-South) in December 2013. Products are provided over tropical Atlantic east of Barbados. This experiment provides column integrated quantities as seen from satellite perspective but with higher spatially resolution (about 1 km footprint) than available from microwave satellites.