This ESSD special issue aims to provide access to datasets collected during the Pallas Cloud Experiment (PaCE) that took place in the subarctic region of Finnish Lapland between 12 September and 15 December 2022. The campaign was hosted by the Finnish Meteorological Institute (FMI) and utilized several different approaches to collect extensive datasets on atmospheric properties: a concurrent ground and airborne in situ approach and remote-sensing measurements. The intensive part of the campaign lasted 1 month, from 15 September to 15 October, and focused on vertical profiling of atmospheric properties. Several European institutes contributed to the PaCE campaign by deploying different instrumentation and platforms. Sammaltunturi station (67°58' N, 24°07' E;560 m a.s.l.), a part of the Pallas Atmosphere–Ecosystem Supersite and Global Atmospheric Watch (GAW) programme, located 170 km north of the Arctic Circle, was utilized as a reference point for all measurements. Sammaltunturi station sits on top of a treeless hill (565 m a.s.l.) and is inside a cloud about 50 % of the time during autumn; thus, it is an ideal place for in situ cloud measurements. The station is equipped with various aerosol, cloud, reactive gas, and meteorology instrumentation. Additionally, a square of reserved airspace, TEMPO D area Pallas, with a side length of 7 km and a ceiling height of 2 km a.g.l. centred on Sammaltunturi station provided a safe playground for uncrewed airborne platforms. Remote-sensing instruments, namely a Doppler lidar HALO StreamLine XR (HALO Photonics), ceilometers (models CL31 and CL61, Vaisala Oyj), and a cloud radar (model RPG FMCW 94 GHz,RPG Radiometric Physics), were deployed around Kenttarova station (67°59' N, 24°14' E; 347 m a.s.l.), which is surrounded by coniferous forest. These instruments operated continuously for the whole campaign (15 September–15 December), although with short technical and maintenance breaks.

The Max Planck Institute (MPI) deployed their Helikite with a payload focused on cloud microphysics and atmospheric turbulence measurements. The Swiss Federal Institute of Technology (EPFL) used another Helikite to measure aerosol physical and optical properties. The Karlsruhe Institute of Technology (KIT) provided their mobile cloud chamber for the investigation of ice-nucleating particles (INPs), a Portable Ice Nucleation Experiment (PINE) unit, at the Sammaltunturi station and also collected INPs on filters using a fixed-wing UAV at different altitudes. The TU Wien (TUW) provided a single-particle Wideband Integrated Bioaerosol Sensor (WIBS-5) for measurements of bacteria, moulds, and other biogenic aerosols at Sammaltunturi station. The University of Hertfordshire provided their Universal Cloud and Aerosol Sounding System (UCASS) for the physical characterization of aerosol and clouds in vertical column using a small fixed-wing UAV. FMI deployed two types of small UAVs: multi-rotor profilers to measure meteorological parameters and particulate matter up to 500 m a.g.l and fixed-wing profilers to measure the aerosol and cloud physical properties and meteorological parameters up to 2000 m a.g.l. Also, the FMI tethered balloon system was deployed for aerosol and cloud measurements.

Review process: all papers of this special issue underwent the regular interactive peer-review process of Earth System Science Data handled by members of the editorial board as well as guest editors designated by the ESSD chief editors.