The science guiding the \EURECA campaign and its measurements are presented. \EURECA comprised roughly five weeks of measurements in the downstream winter trades of the North Atlantic — eastward and south-eastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, \EURECA marked a turning point in our ability to observationally study factors influencing clouds in the trades, how they will respond to warming, and their link to other components of the earth system, such as upper-ocean processes or, or the life-cycle of particulate matter. This characterization was made possible by thousands (2500) of sondes distributed to measure circulations on meso (200 km) and larger (500 km) scales, roughly four hundred hours of flight time by four heavily instrumented research aircraft, four global-ocean class research vessels, an advanced ground-based cloud observatory, a flotilla of autonomous or tethered measurement devices operating in the upper ocean (nearly 10000 profiles), lower atmosphere (continuous profiling), and along the air-sea interface, a network of water stable isotopologue measurements, complemented by special programmes of satellite remote sensing and modeling with a new generation of weather/climate models. In addition to providing an outline of the novel measurements and their composition into a unified and coordinated campaign, the six distinct scientific facets that \EURECA explored — from Brazil Ring Current Eddies to turbulence induced clustering of cloud droplets and its influence on warm-rain formation — are presented along with an overview \EURECA’s outreach activities, environmental impact, and guidelines for scientific practice.

In this study, we discuss a new mountain peak observatory in the United Arab Emirates (UAE). Using coordinated scan patterns, a Doppler lidar and cloud radar were employed to study seedable convective clouds, and identify pre-convection initiation (CI) clear-air signatures. The instruments were employed for approximately two years in an extreme environment with a high vantage point for observing valley wind flows and convective cells. The instruments were configured to run synchronized polar (PPI) scans at 0°, 5°, and 45° elevation angles and vertical cross-section (RHI) scans at 0°, 30°, 60, 90°, 120°, and 150° azimuth angles. Using this output imagery, along with local C-band radar and satellite data, we were able to identify and analyze several convective cases. To illustrate our results, we selected two cases in unstable conditions - the 5 and 6 September 2018. In both cases, we observed areas of convergence/divergence, particularly associated with wind flow around a peak 2 km to the south-west. The extension of these deformations were visible in the atmosphere as high as 3 km above sea level. Subsequently, we observed convective cells developing in the same directions – apparently connected with these phenomena. The cloud radar images provided detailed observations of cloud structure, evolution, and precipitation. In both convective cases, pre-convective signatures were apparent before CI, in the form of convergence, wind shear structures, and updrafts. These results demonstrate the value of synergetic observations for understanding convection initiation, improvement of forecast models, and cloud seeding guidance.