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As part of the EUREC4A (Elucidating the role of cloud–circulation coupling in climate) field campaign, which took place in January and February 2020 over the western tropical Atlantic near Barbados, the French SAFIRE ATR42 research aircraft (ATR) conducted 19 flights in the lower troposphere. Each flight followed a common flight pattern that sampled the atmosphere around the cloud base level, at different heights of the subcloud layer, near the sea surface and in the lower free troposphere. The aircraft's payload included a backscatter lidar and a Doppler cloud radar that were both horizontally oriented; a Doppler cloud radar looking upward; microphysical probes; a cavity ring-down spectrometer for water isotopes; a multiwavelength radiometer; a visible camera; and multiple meteorological sensors, including fast rate sensors for turbulence measurements. With this instrumentation, the ATR characterized the macrophysical and microphysical properties of trade-wind clouds together with their thermodynamical, turbulent and radiative environment. This paper presents the airborne operations, the flight segmentation, the instrumentation, the data processing and the EUREC4A datasets produced from the ATR measurements. It shows that the ATR measurements of humidity, wind and cloud base cloud fraction measured with different techniques and samplings are internally consistent; that meteorological measurements are consistent with estimates from dropsondes launched from an overflying aircraft (the High Altitude and LOng Range Research Aircraft, HALO); and that water-isotopic measurements are well correlated with data from the Barbados Cloud Observatory. This consistency demonstrates the robustness of the ATR measurements of humidity, wind, cloud base cloud fraction and water-isotopic composition during EUREC4A. It also confirms that through their repeated flight patterns, the ATR and HALO measurements provided a statistically consistent sampling of trade-wind clouds and of their environment. The ATR datasets are freely available at the locations specified in Table 11.

During the EUREC4A field experiment that took place over the tropical Atlantic Ocean east of Barbados, the French ATR 42 environment research aircraft of SAFIRE aimed to characterize the shallow cloud properties near cloud base and the turbulent structure of the subcloud layer. For this purpose, the aircraft payload included radar and lidar remote sensing, microphysical probes, a laser spectrometer, and meteorological sensors. In particular, the aircraft was equipped with a five-hole radome nose as well as several temperature and moisture sensors allowing for measurements of wind, temperature and humidity at 25 Hz. This paper presents the high-frequency measurements made with these sensors and their translation in terms of turbulent fluctuations, turbulent moments and characteristic length scales of turbulence. A particular focus is on the calibration and the quality control of the air moisture measurements, which remain a challenge at fine scales. Level-2 and Level-3 data are distributed as an ensemble of NetCDF files available to the public at AERIS (https://doi.org/10.25326/128, Lothon and Brilouet, 2020).