Vertical Distribution Of Cloud Condensation Nuclei In Marine And Continental Air Masses Over Europe And Their Connection To The Cloud Droplet Number Distribution In Warm Clouds

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The number of available cloud condensation nuclei (CCN) is an important parameter influencing cloud microphysical properties such as cloud droplet number concentration (CDNC) and size distribution. CDNC and droplet size control cloud radiative properties and lifetime leading to a complex feedback in the earths energy balance. Current climate models are often based on assumptions concerning CCN number concentrations and other CCN related properties (e.g. hygroscopicity), as for wide areas of the globe representative data are missing. If existing, measurements of CCN and their properties are usually performed near ground and thus not, with the exception of mountain sites, in the altitude relevant for cloud formation processes. For the well-mixed marine boundary layer in the Caribbean it was however observed that ground based CCN properties seem to be representative also for the cloud forming regions. In this proposed project we want to evaluate if ground-based CCN measurements are representative, and if yes under which conditions, for the level of cloud formation, which would simplify the application of CCN data in models strongly. Thereto, the validity of the finding in the Caribbean shall be tested for two contrasting environments, i.e., a marine and a continental environment. Concerning the marine environment, a measurement campaign on the Azores archipelago (Portugal) is planned. We will combine continuous available CCN data from the Azores Eastern North Atlantic (ENA) site at Graciosa Island (at sea level) with campaign wise measurements at Mt. Pico station (Pico Island, 2225 m asl), and CCN as well as CDNC measurements on the helicopter-borne measurement platform ACTOS (Airborne Cloud Turbulence Observation System) to close the vertical gap between sea level and mountain-site data. The continental ground-based CCN measurements are carried out continuously at the ACTRIS (Aerosols Clouds and Trace gases Research InfraStructure network) station Melpitz. The vertical CCN and CDNC distribution will be measured at Melpitz in several one-week campaigns once per season by means of balloon launches within the three year time frame of the project. Furthermore we will quantitatively connect via the utilization of the aerosol-cloud interaction (ACI) metric the below cloud in-situ measured CCN properties (i.e. number and hygroscopicity) to in-cloud in-situ measured CDNC. A sensitivity study with a cloud parcel model driven by the real atmospheric measurements will be carried out; thereby gaining insight into the supersaturation regimes of freshly formed real clouds. The collected data itself, the expected insights into CCN properties and their vertical distributions, and the envisioned quantitative connection between CCN and CDNC will be of great value in the context of understanding and modeling cloud droplet activation and cloud microphysical properties in, e.g., climate models.