International audienceActive remote sensing instruments such as lidar and radar allow us to accurately detect the presence of clouds and give information on their vertical structure and phase. In order to better address cloud radiative impact over the Arctic area, a combined analysis based on lidar and radar ground-based and A-Train satellite measurements was carried out to evaluate the efficiency of cloud detection, as well as cloud type and vertical distribution, over Eureka (80 °N, 86 °W) between June 2006 and May 2010. CALIPSO and CloudSat data were first compared to the independent ground-based cloud measurements. Seasonal and monthly trends from independent observations were found to be similar amongst all datasets except when compared to the weather station observations, due to the large reported fraction of ice crystals suspended in the lower troposphere in winter. Further investigations focused on satellite observations collocated in space and time with ground-based data. Cloud fraction occurrences from ground-based instruments were well correlated with both CALIPSO operational products and combined CALIPSO-CloudSat retrievals with a hit rate of 85 %. The hit rate was only 77 % for CloudSat products. The misdetections were mainly attributed to a) undetected low-level clouds due to sensitivity loss, and b) missed clouds because of the distance between the satellite track and the station. The spaceborne lidar-radar synergy was found to be essential to have a complete picture of the cloud vertical profile down to 2 km. Errors are quantified and discussed

With their extensive coverage, marine low clouds greatly impact global climate. Presently, marine low clouds are poorly represented in global climate models, and the response of marine low clouds to changes in atmospheric greenhouse gases and aerosols remains the major source of uncertainty in climate simulations. The Eastern North Atlantic (ENA) is a region of persistent but diverse subtropical marine boundary layer clouds, whose albedo and precipitation are highly susceptible to perturbations in aerosol properties. In addition, the ENA is periodically impacted by continental aerosols, making it an excellent location to study the cloud condensation nuclei (CCN) budget in a remote marine region periodically perturbed by anthropogenic emissions, and to investigate the impacts of long-range transport of aerosols on remote marine clouds. The Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA) campaign was motivated by the need of comprehensive in-situ measurements for improving the understanding of marine boundary layer CCN budget, cloud and drizzle microphysics, and the impact of aerosol on marine low cloud and precipitation. The airborne deployments took place from June 21 to July 20, 2017 and January 15 to February 18, 2018 in the Azores. The flights were designed to maximize the synergy between in-situ airborne measurements and ongoing long-term observations at a ground site. Here we present measurements, observation strategy, meteorological conditions during the campaign, and preliminary findings. Finally, we discuss future analyses and modeling studies that improve the understanding and representation of marine boundary layer aerosols, clouds, precipitation, and the interactions among them.