We provide data from the autonomous surface vehicle HALOBATES. It gathered Essential Climate Variables (ECVs) like sea surface temperature (SST) and salinity (SSS). Data were collected during RV Meteor cruise M211 from 14 June (Nice, France) to 27 July 2025 (Ponta Delgada, Portugal) in the Mediterranean Sea and the Central Atlantic Ocean. HALOBATES measured conductivity and temperature at seven depths. Vertical resolution was ~10 centimetres. Depths spanned the near-surface layer (NSL, at 30, 40, 50, 60, 85, and 100 cm) to the sea-surface microlayer (SML) with a sampling depth of the upper ~ 80 µm. NSL water was collected with tubes on a bow-mounted ladder. SML water was collected using six partially submerged glass disks. Water from all sampled depths, including the SML, reached the CTD sensors via a pumped flow-through system. Salinity was corrected with discrete water samples. Additionally, offsets between the CTDs were corrected. Additional in-situ temperature sensors corresponding to depths of the flow-through system inlets and CTDs (30, 50 and 85 cm depth) were mounted beneath the catamaran. Two data loggers with meteorological stations recorded wind speed, air temperature, relative humidity, solar radiation, GPS positions, and atmospheric conditions. Upward and downward facing pyranometers and pyrgeometers mounted on the research vessel measured net radiative fluxes for short- and longwave radiation. A disdrometer mounted on the vessel measured precipitation. The research vessel kept an average distance of 500 metres from HALOBATES which was operated manually or via autopilot. Autopilot involved pre-defined waypoints whilst manual involved steering HALOBATES with a remote control or drifting with surface currents during station work. The dataset includes quality flags 0-4 with flags 1 and 2 are ready for use. See metadata for more information.

Quality Flag: Name - Implication0: Unknown - No information on data quality1: Good data - Certainly good data point2: Probably good data - Likely good data3: Questionable data - Data point needs extra attention4: Bad Data - Do not use