BOWTIE: ship-based measurements of atmosphere and ocean within the moist tropical Atlantic

Abstract. As part of BOWTIE (German: Beobachtung von Ozean und Wolken - Das Trans ITCZ Experiment), the German research vessel FS Meteor navigated the moist tropics of the Atlantic Ocean for 40 days in summer 2024, with an east-west trajectory. The journey started in the port of Mindelo, Cape Verde, on August 16, and finished in the port of Bridgetown, Barbados, on September 24. The objective was to measure properties of the atmosphere, upper-ocean, and air-sea interface within the Intertropical Convergence Zone (ITCZ), under a variety of wind, convection, and sea surface temperature regimes. Using a set of 29 instruments/platforms, BOWTIE sampled the near-surface conditions of the atmosphere and ocean with high temporal resolution. This included continuous measurements of: the 2-D wind field within the lowest 2 km of the atmosphere, near-surface ocean currents, cloud and precipitation properties. Profiles of the ocean state and atmospheric thermodynamics and kinematics were obtained both continuously and at discrete intervals. Furthermore, dedicated stations sampled biochemical properties of the upper-ocean. Complementing BOWTIE observations, FS Meteor hosted further dedicated field campaigns for 3D cloud and precipitation properties, as well as intensive measurements of the atmospheric boundary layer. This manuscript provides an overview of the extensive instrumentation and data collected during BOWTIE. In addition, it addresses two key aspects based on these observations. First, it examines the range and uncertainties of selected quantities measured by multiple instruments, including column-integrated water vapor, rain detection, surface ocean currents, and sea surface temperature. Second, it illustrates the diversity of sampled weather regimes through two representative cases: calm doldrum conditions and a gusty, precipitating convective state.