EUREC<sup>4</sup>A

Abstract

Abstract. The science guiding the EUREC4A campaign and its measurements is presented. EUREC4A comprised roughly 5 weeks of measurements in the downstream winter trades of the North Atlantic – eastward and southeastward of Barbados. Through its ability to characterize processes operating across a wide range of scales, EUREC4A 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 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 400 h of flight time by four heavily instrumented research aircraft; four global-class research vessels; an advanced ground-based cloud observatory; scores of autonomous observing platforms operating in the upper ocean (nearly 10 000 profiles), lower atmosphere (continuous profiling), and along the air–sea interface; a network of water stable isotopologue measurements; targeted tasking of satellite remote sensing; and modeling with a new generation of weather and 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 EUREC4A explored – from North Brazil Current rings to turbulence-induced clustering of cloud droplets and its influence on warm-rain formation – are presented along with an overview of EUREC4A's outreach activities, environmental impact, and guidelines for scientific practice. Track data for all platforms are standardized and accessible at https://doi.org/10.25326/165 (Stevens, 2021), and a film documenting the campaign is provided as a video supplement.

JOANNE: Joint dropsonde Observations of the Atmosphere in tropical North atlaNtic meso-scale Environments

“…Most circles were flown along a fixed circular path, called the EUREC 4 A-circle (Stevens et al, 2021), which was planned with the center coordinates as 13.30 • N, 57.72 • W and a diameter of roughly 220 km. The location of the sonde launches shown in Fig.…”

“…It adopted Barbados as its base of operations and focused its measurements in an area extending eastward of the Barbados Cloud Observatory (BCO; Stevens et al, 2016). EUREC 4 A's initial scientific motivation, its subsequent evolution and the final execution are described in Bony et al (2017) and Stevens et al (2021). As these papers emphasize, a central element of EUREC 4 A was the airborne release of dropsondes to characterize the mesoscale meteorological environment of cloud fields in the trades.…”

Deployment of the C-band radar Poldirad on Barbados during EUREC<sup>4</sup>A

“…EUREC 4 A is an international initiative in the scope of the World Climate Research Programme's Grand Challenge on Clouds, Circulation and Climate Sensitivity. The field phase of EUREC 4 A took place between 20 January and 20 February 2020 in the region east of Barbados (Bony et al, 2017;Stevens et al, 2021).…”

“…In order to respond to those questions, remote sensing and in situ observations on various scales were performed to investigate clouds and precipitation and their atmospheric and oceanic environment (Stevens et al, 2021). Four research vessels, four research aircraft, a large number of autonomous boats, and aircraft were involved.…”

“…Because of the lack of continuous observations, various field campaigns have been performed in the Atlantic trade wind region to investigate in detail the role of shallow maritime cumuli and their relation to air-sea interaction and global circulation: BOMEX 1969 (e.g., Fleagle, 1972;Holland and Ras-musson, 1973), GATE 1974(e.g., Kuettner et al, 1974Kuettner and Parker, 1976), ASTEX 1992 (Albrecht et al, 1995), and RICO 2004/05 (e.g., Rauber et al, 2007. In order to further elucidate the thermodynamic and dynamic environment of maritime clouds and their organization, the EUREC 4 A (Elucidating the role of clouds-circulation coupling in climate) campaign was planned (Bony et al, 2017) and performed in January and February 2020 in the trade wind zone east of Barbados (Stevens et al, 2021).…”