Abstract
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 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 (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.
Highlights
20 The interaction of trade-wind clouds with their environment is at the center of fundamental questions such as the role of clouds in climate sensitivity
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 (HALO), and that water isotopic measurements are well correlated with data from the Barbados Cloud Observatory
It is distributed as a set of NetCDF files which include the following products: particle size distribution (PSD), total particle concentration (NT) and liquid water content (LWC, assuming particles are spherical with a density of 1 g cm−3), all processed at a frequency of 1 Hz. 515 The data are distributed for two levels of processing: the level 2 dataset is associated with single instruments while the level 3 dataset corresponds to a combined PMA dataset that merges CDP-2 and 2D-S data into a single composite spectrum that spans the range 2 μm to 2.55 mm
Summary
20 The interaction of trade-wind clouds with their environment is at the center of fundamental questions such as the role of clouds in climate sensitivity. To elucidate the couplings between clouds and circulation, the 25 nucleus of the experimental strategy was based on the coordinated and repeated flight plans of two core platforms : the High Altitude and Long-range Research Aircraft (HALO) operated by the German Aerospace Center (Konow et al, 2021), and the ATR-42 (hereafter referred to as ATR) operated by the French Service des Avions Français Instrumentés pour la Recherche en Environnment (SAFIRE). The instrumentation was chosen to promote redundancy or complementarity 50 of sensors and measurement techniques This redundancy was important for the post-processing and calibration of the data, it was essential to assess the robustness of the ATR measurements of cloud fraction, humidity and winds.
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