The research aircraft DO-128, call sign D-IBUF, of the IFF (TU Braunschweig) measures numerous meteorological and chemical variables to get a better understanding of the atmospheric processes which cause the development of precipitation. The aircraft starts from the Baden Airpark and flys among different flight pattern which are described in the flight protocols. The meteorological variables are static pressure and dynamic pressure at the nose boom, surface temperature, humidity mixing ratio by a lyman-alpha sensor, dewpoint temperature by a dewpoint-mirror, relative humidity by an aerodata-humicap, air temperature by a PT-100 sensor, vertical and horizontal wind components by a five-hole probe and GPS, turbulence (100 Hz), shortwave (pyranometer) and longwave (pyrgeometer) radiance in upper und lower half space. The chemical variables are mole fractions of ozone, carbon dioxide, carbon monoxide, nitrogen dioxide, nitrogen monoxide and nitric oxides (NOx). There are also a few variables for the position and the velocity of the aircraft stored in the data file. Additionally to the measurements by the aircraft, up to 30 drop-sondes can be dropped out of the aircraft. By using these sondes, vertical profiles of temperature, pressure, humidity and wind can be detected (see also the meta data describing the drop-sonde data). Special events are also marked in the data files by the event counter (e.g. dropping times of the drop-sondes, marks concerning the flight patterns etc.). The specific action or flight manoeuvre indicated by the event_number can be identified in the flight protocol.

The energy balance station run by University of Bonn measured high-frequency (10 Hz) eddy-covariance raw data with a CSAT3 (Campbell Scientific, Inc.) sonic anemometer and a LI-7500 (LI-COR Biosciences) hygrometer above the target land use type meadow. The measuring set-up was continuously running during the entire COPS measurement period in order to provide a complete time series of the turbulent fluxes of momentum, sensible and latent heat as well as carbon dioxide. Post-processing was performed using the software package TK2 (developed by the Department of Micrometeorology, University of Bayreuth) which produces quality assured turbulent flux data with an averaging interval of 30 min. The documentation and instruction manual of TK2 (see entry cops_nebt_ubt_info_1) and additional references about the applied flux corrections and post-field data quality control (see entry cops_nebt_ubt_info_2) as well as a document about the general handling of the flux data can be found in supplementary pdf-files within the energy balance and turbulence network (NEBT) experiment of the data base. The turbulent flux data in this data set are flagged according to their quality and checked for an impact of possible internal boundary layers. Additionally, the flux contribution from the target land use type intended to be observed to the total flux measured was calculated applying footprint modeling. Information and references about the internal boundary layer evaluation procedure and the footprint analysis are also given in additional info pdf-files. Pictures of the footprint climatology of the station as related to the land use and to the spatial distribution of the quality flags are included in the corresponding additional info pdf-file.

EARLINET climatological lidar observations are performed on a regular schedule of one daytime measurement per week around noon (on Monday), when the boundary layer is usually well developed, and two night-time measurements per week (on Monday and Thursday), with low background light, in order to perform Raman extinction measurements. This regular schedule for observations minimizes the bias in the dataset possibly related to specific measurement conditions. The resulting dataset is used to obtain unbiased data for climatological studies. This dataset contains profiles of aerosol extinction, backscatter and lidar ratio. Several aerosol extinction/backscatter datasets can be present for the same climatological measurement in order to provide profiles either with a better temporal resolution or with an extended height range by using a larger temporal average. This is by far the largest ground based dataset on the aerosol vertical distribution, and it is the only one which is collected systematically and is covering a whole continent.

The energy balance stations run by University of Bayreuth measured either high-frequency (20 Hz) eddy-covariance raw data with a CSAT3 (Campbell Scientific, Inc.) sonic anemometer and a LI-7500 (LI-COR Biosciences) hygrometer or turbulent fluxes of momentum, sensible and latent heat with a USA-1 (METEK GmbH, Germany) sonic anemometer and two psychrometers (Frankenberger) above different the target land use types. The measuring set-up was continuously running during the entire COPS measurement period in order to provide a complete time series of the turbulent fluxes of momentum, sensible and latent heat as well as carbon dioxide. Post-processing was performed using the software package TK2 (developed by the Department of Micrometeorology, University of Bayreuth) which produces quality assured turbulent flux data with an averaging interval of 30 min. The documentation and instruction manual of TK2 (see entry cops_nebt_ubt_info_1) and additional references about the applied flux corrections and post-field data quality control (see entry cops_nebt_ubt_info_2) as well as a document about the general handling of the flux data can be found in supplementary pdf-files within the energy balance and turbulence network (NEBT) experiment of the data base. The turbulent flux data in this data set are flagged according to their quality and checked for an impact of possible internal boundary layers. Additionally, the flux contribution from the target land use type intended to be observed to the total flux measured was calculated applying footprint modeling. Information and references about the internal boundary layer evaluation procedure and the footprint analysis are also given in the additional pdf-files. Pictures of the footprint climatology of the station as related to the land use and to the spatial distribution of the quality flags are included in the supplementary pdf-files corresponding to the individual station.

The 9 m profile mast run by University of Bayreuth continuously measured profiles of the wind speed, the air temperature and the water vapor pressure above a corn field with a sampling frequency of 1 Hz averaged to 1 min values within the data logger. Six cup anemometers and five psychrometers have been mounted in different heights. After a check for plausibility the 1 min values have been averaged to 30 min intervals, which are provided in this data set. The following instruments have been installed for the parameters given below: - wind speed: F460 cup anemometer (Climatronics Corp.) - temperature and water vapor pressure: electrically aspirated psychrometer (Frankenberger) The water vapor pressure has been calculated from the measured dry and moist thermometer temperatures of the psychrometer according to Sprung's psychrometer formula.

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

EARLINET climatological lidar observations are performed on a regular schedule of one daytime measurement per week around noon (on Monday), when the boundary layer is usually well developed, and two night-time measurements per week (on Monday and Thursday), with low background light, in order to perform Raman extinction measurements. This regular schedule for observations minimizes the bias in the dataset possibly related to specific measurement conditions. The resulting dataset is used to obtain unbiased data for climatological studies. This dataset contains profiles of aerosol extinction, backscatter and lidar ratio. Several aerosol extinction/backscatter datasets can be present for the same climatological measurement in order to provide profiles either with a better temporal resolution or with an extended height range by using a larger temporal average. This is by far the largest dataset on the aerosol vertical distribution, and it is the only one which is collected systematically and is covering a whole continent.

The geographical distribution of the EARLINET stations is particularly suitable for dust observation, with stations located all around the Mediterranean (from the Iberian Peninsula in the West to the Greece and Bulgaria and Romania in the East) and in the center of the Mediterranean (Italian stations) where dust intrusions are frequent, and with several stations in the central Europe where dust penetrates occasionally. A suitable observing methodology has been established within the network, based on Saharan dust alerts distributed to all EARLINET stations. The dust alert is based on the operational outputs (aerosol dust load) of the DREAM (Dust REgional Atmospheric Model), and the Skiron models. The alerts are diffused 24 to 36 hours prior to the arrival of dust aerosols over the EARLINET sites. Runs of measurements longer than 3-hour observations, typical for the EARLINET climatological measurements are performed at the EARLINET stations in order to investigate the temporal evolution of the dust events. All aerosol backscatter and extinction profiles related to observations of Saharan dust layers are collected in the "Saharan dust" category of the EARLINET database.

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.

Aerosols originating from volcanic emissions have an impact on the climate: sulfate and ash particles from volcanic emissions reflect solar radiation, act as cloud condensation and ice nuclei, and modify the radiative properties and lifetime of clouds, and therefore influence the precipitation cycle. These volcanic particles can also have an impact on environmental conditions and could be very dangerous for aircraft in flight. In addition to the routine measurements, further EARLINET observations are devoted to monitor volcano eruptions. The EARLINET volcanic dataset includes extended observations related to two different volcanoes in Europe Mt. Etna (2001 and 2002 eruptions), and the Eyjafjallajökull volcano in Iceland (April - May 2010 eruption). This dataset includes also recent events of volcanic eruptions in the North Pacific region (2008-2010) that emitted sulfuric acid droplets into the upper troposphere - lower stratosphere (UTLS) height region of the northern hemisphere. The EARLINET volcanic observations in the UTLS are complemented by the long-term stratospheric aerosol observations collected in the Stratosphere category.