This dataset contains the number concentrations of particles with dry diameters larger than 100 nm (N100) calculated from particle number size distribution measurements. The dataset includes varying lengths of daily averaged data from 35 measurement stations worldwide, collected during the period from 2003 to 2019. The dataset was utilized in the study titled “Global fields of daily accumulation-mode particle number concentrations using in situ observations, reanalysis data, and machine learning” 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.