Das Projekt "Freie troposphaerische Aerosole und ihre Vermischung mit der marinen Grenzschicht" wird vom Umweltbundesamt gefördert und von Max-Planck-Institut für Kernphysik durchgeführt. Objective: To provide the necessary data to incorporate aerosols into global climate models and to reduce the uncertainty in the calculation of climate forcing by General Information: FREETROPE is one of five projects that together form the European contribution to the experimental phase of IGAC s second Aerosol Characterisation Experiment (ACE-2). The specific task of FREETROPE is to describe one part of the aerosol life cycle in the marine environment and how it is perturbed by anthropogenic emissions. This is accomplished by characterising the aerosol in the free troposphere (FT) of the sub-tropical North Atlantic, and by performing systematic comparisons with the aerosol in the marine boundary layer (MBL). Using the Cessna Citation the FT aerosol is characterised over larger areas. These characterisations will form the basis for process studies in FREETROPE focusing on 1) the nucleation and growth of aerosols in the clean and perturbed FT, and 2) their possible entrainment in the MBL, with subsequent effects on MBL aerosols and cloud processes. A description of these processes together with other processes, e.g. cloud processes, studied in the other ACE-2 projects LAGRANGIAN and HILLCLOUD will give a unique possibility to give a description of the full life cycle of the atmospheric particles. FREETROPE will operate from Tenerife, doing continuous simultaneous measurements at a coastal MBL station (40 m), and a FT station (Izana, 2360 m). The Cessna Citation will complement these measurements with 50 hours of flight hours between 2300 and 12000 m. At the ground sites, the hygroscopic properties and state of mixing will further be investigated. On all platforms aerosol measurements will be complemented with gas measurements to the extent that they provide information about precursors to aerosol formation and condensational growth, or can indicate the origin of air masses. The Citation will carry a unique payload of mass spectrometers and aerosol instrumentation to study nucleation of H2SO4 and possibly other species (NH4Cl, (NH4)H2SO4 and organics) in the free troposphere. The two ground based station form an ideal set up to study the role of FT-MBL entrainment. The measurements will be supported by trajectory analysis, aerosol dynamic modelling and regional scale modelling that will make a first integration of the data. Prime Contractor: Stockholms Universitet, Department of Meteorology; Stockholm; Schweden.