Particles containing meteoric material were observed in the lower stratosphere during five aircraft research missions in recent years. Single particle laser ablation technique in a bipolar configuration was used to measure the chemical composition of particles in a size range of approximately 150 nm to 3 µm. The five aircraft missions, conducted between 2014 and 2018, cover a latitude range from 15 to 68°N. In total, more than 330 000 single particles were analyzed. A prominent fraction (more than 50 000) of the analyzed particles was characterized by strong abundances of magnesium, iron, and rare iron oxide compounds, together with sulfuric acid. This particle type was found almost exclusively in the stratosphere and is interpreted as meteoric material immersed or dissolved in stratospheric sulfuric acid particles. Below the tropopause the fraction of this particle type decreases sharply. However, small abundances were observed below 3000 m a.s.l. in the Canadian Arctic and also at the Jungfraujoch high altitude station (3600 m a.s.l.). Thus, the removal pathway by sedimentation and/or mixing into the troposphere is confirmed. Our data show that particles containing meteoric material are present in the lower stratosphere in very similar relative abundances, regardless of latitude or season. This finding suggests that the meteoric material is transported from the mesosphere into the stratosphere in the downward branch of the Brewer-Dobson-Circulation and efficiently distributed towards low latitudes by isentropic mixing. As a result, meteoric material is found in particles of the stratospheric Junge layer at all latitudes.

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.