Daily Measurements of Number Concentrations (N100 and N50) at 74 stations (2003-2024)

This dataset contains the number concentrations of particles with dry diameters larger than 100 nm (N100) and larger than 50 nm (N50) calculated from particle number size distribution measurements. The dataset includes varying lengths of daily averaged data from 74 measurement stations worldwide, collected during the period from 2003 to 2024. The dataset was utilised in a study titled “A 21-year global dataset of particle number concentrations for aerosol-cloud interaction studies" by Ovaska et al. (2026) to train and validate machine learning models. For more detailed information on the dataset, including the specific measurement periods, data processing methods, and station details, please refer to the publication. The dataset is organised to contain one NetCDF file per station, except EGB and SGP measurements are split into two files. The variables in the files are: time Time stamp of each observation (UTC), beginning of the averaging period latitude Latitude of the measurement station in decimal degrees. longitude Longitude of the measurement station in decimal degrees. N50 Number concentration of particles larger than 50 nm (per cm³).Derived from particle number size distribution measurements; includes days with at least 21 hours of valid data. N100 Number concentration of particles larger than 100 nm (per cm³).Derived from particle number size distribution measurements; includes days with at least 21 hours of valid data. min_diameter Smallest particle diameter measured (nm). If the minimum size varies during the day, this reports the largest minimum value Variable for quality control: for N100 min_diam should be below 100 nm and for N50 min_diam should be below 50 nm for reliable number concentration calculation. max_diameter Largest particle diameter used for N100 and N50 calculation (nm). If the maximum size varies during the day, this reports the smallest maximum value Variable for quality control: shows the maximum diameter used for calculating N100 and N50. index Index variable identifying each record (dimension for the dataset). Additionally, each file contains following metadata information about the station: station, country, latitude, longitude, and abbreviation.