A Synergistic Analysis of Cloud Cover and Vertical Distribution from A-Train and Ground-Based Sensors over the High Arctic Station Eureka from 2006 to 2010

Active 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.