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We present here the first cloud condensation nuclei (CCN) concentration profiles derived from measurements with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), for different aerosol types at a supersaturation of 0.15%. CCN concentrations, along with the corresponding uncertainties, were inferred for a nighttime CALIPSO overpass on 9 September 2011, with coincident observations with the Facility for Airborne Atmospheric Measurements (FAAM) BAe-146 research aircraft, within the framework of the Evaluation of CALIPSO's Aerosol Classification scheme over Eastern Mediterranean (ACEMED) research campaign over Thessaloniki, Greece. The CALIPSO aerosol typing is evaluated, based on data from the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis. Backward trajectories and satellite-based fire counts are used to examine the origin of air masses on that day. Our CCN retrievals are evaluated against particle number concentration retrievals at different height levels, based on the ACEMED airborne measurements and compared against CCN-related retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors aboard Terra and Aqua product over Thessaloniki showing that it is feasible to obtain CCN concentrations from CALIPSO, with an uncertainty of a factor of two to three. [ABSTRACT FROM AUTHOR]

It is widely accepted that aerosols impact the formation, the optical properties and the life cycle of clouds, aerosol-cloud interactions (ACI) being the largest source of uncertainty in climate change studies. Specifically, for warm clouds, ACI depend on the cloud condensation nuclei (CCN) number concentration. So far, satellite-based studies focusing on ACI utilize observations of aerosol optical depth (AOD) or Aerosol Index (AI: AOD multiplied by the Ångström exponent) considering them as a proxy for the number of aerosols in the atmosphere and not CCN observations per se. Here, we present a first effort to calculate CCN concentration profiles from CALIOP/CALIPSO satellite observations based on recently proposed parameterizations. CCN concentrations along with the corresponding uncertainties are calculated for different tropospheric aerosol types and for different supersaturation levels. Our data are compared against CCN retrievals from the MODIS/Aqua satellite-based product which are available over oceanic areas only. Then, the data are validated against particle number concentrations at different height levels from airborne measurements over the greater Thessaloniki area in northern Greece. The validation data were retrieved from the FAAM (Facility for Airborne Atmospheric Measurements) BAe-146 research aircraft during the ACEMED (evaluation of CALIPSO's Aerosol Classification scheme over Eastern MEDiterranean) campaign that took place in September 2011. We acknowledge support of this work by the project "PANhellenic infrastructure for Atmospheric Composition and climatE change" (MIS 5021516) which is implemented under the Action "Reinforcement of the Research and Innovation Infrastructure", funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund). [ABSTRACT FROM AUTHOR]