Coarse mode aerosol particle size distribution collected in the Southern Ocean in the austral summer of 2016/2017, during the Antarctic Circumnavigation Expedition. ***** Dataset abstract ***** The authors would highly appreciate to be contacted if the data is used for any purpose. We measured coarse mode aerosol particle size distributions with an aerodynamic particle sizer (APS, model TSI 3321) at a time resolution of five minutes during the Antarctic Circumnavigation Expedition (ACE). The diameter range is 0.7 to 19 µm. Particles in this size range are indicative of primary sea spray aerosol, biological particles and potentially long-range transported mineral dust. These particles are also important for cloud formation as they act as cloud condensation nuclei or ice nucleating particles, the latter especially in the case of biological particles and mineral dust. Typically the instrument reports data starting from particles with a diameter greater than 500 nm, however, particle number concentrations in the channels below 723 nm were overestimated, which is a common artefact with this instrument. The data have been cleaned from the influence of the exhaust of the research vessel. Temporal coverage is from December 20, 2016 to April 10, 2017. We give five-minute averaged data as dN/dlog(dp), where dN is the particle number concentration per measured size bin normalized over the logarithm of the bin width. The bin width is defined as the distance between two diameters. They are spaced equally in log-space with dlog(dp) = log(d_n+1/d_n) = 1/32. To derive the total particle number concentration one has to integrate over the diameter range taking into account the normalization by dlog(dp). ***** Original data collection ***** We operated a TSI APS model 3321 aerodynamic particle sizer with five-minute time resolution. The instrument was placed behind a standard Global Atmosphere Watch whole air inlet (10.1038/sdata.2017.3) in an aerosol container constructed by the Paul Scherrer Institute situated on the foredeck of the R/V Akademik Tryoshnikov. More about this set-up can be found in the cruise report here: https://doi.org/10.5281/zenodo.1443511. Original output was stored as text files in real-time on a computer situated in the PSI laboratory container. The Aerosol Instrument Manager (AIM) acquisition software from TSI for APS 3321 was used to collect the data. No data processing was done during data collection. ***** Data processing ***** The data were corrected for inlet line losses which were experimentally determined by operating one condensation particle counter (CPC) at the beginning of the inlet line and another at the connector for the APS. Different sizes of particles were generated (500, 600, 700, 800 nm). The average loss is 17 % in that size range. Losses at higher diameters might be larger, but could not be tested. Data were processed using the software, Igor Pro, version 6.37. ***** Quality checking ***** The data have been cleaned from exhaust gas based on the spikiness of the total particle number concentration and the CO2 concentrations (10.5281/zenodo.2636690, 10.5281/zenodo.2636779, respectively). Exhaust influence on the data was identified as follows: The particle number concentration as measured by the CPC 3022 was used as the basis. First the absolute value of the ratio of the raw over the smoothed signal (running average over 12 points for five-minute time resolution data, which represents a curve similar to a baseline) was calculated. Ratio values that are larger than 1.24 and smaller 0.51 were flagged. The same was done for ratios of the raw and smoothed CO2 data with the thresholds being 1.2 and 0.8. In addition, since exhaust influence is characterized by abrupt concentration changes, subsequent values of the raw particle number concentration time series that were more than 50 cm^-3 apart were flagged. Finally, the flagged and original time series were compared by eye to identify any further values influenced by exhaust. The natural variability in number concentration is evident in timescales of hours rather than seconds, which are characteristics for exhaust plumes. New particle formation events can happen on timescales shorter than one hour: those were not eliminated. There are no standards to our knowledge for APS data quality checks except for instrument intercomparison. The size determination of the instruments was tested in August 2018, showing high accuracy for diameters up to 1 µm. The APS overestimated the measured particle size potentially by 22 % at diameters larger than 3 µm. The particle number concentrations are within +/- 10 % uncertainty. The number concentrations have been corrected for inlet line losses (17 %, see data processing section) that were determined experimentally. Data quality can be assessed only during calibrations and instrument intercomparisons. ***** Standards ***** We follow the best practice that we are aware of in the respective scientific community. ***** Further information for interpreting and using the dataset ***** Detection limit: All reported data are above detection limit. Timescales: The timescales of the main features of the data vary from minutes or shorter (sea spray generation) to hours (regional transport of particles) to days (synoptic weather systems that remove particles through precipitation and long-range transportation). Interpolation: Interpolation of missing values is NOT meaningful due to the inherently high variability. Aggregation to lower temporal resolution: This depends on the research question. The data set features a number of environmental processes that happen on timescales from minutes to days. Averaging will eliminate shorter term signals, but could emphasize longer term features. For more information, see Schmale et al. (2019, in review) “Overview of the Antarctic Circumnavigation Expedition Study of Preindustrial-like Aerosols and their Climate Effects (ACE-SPACE)”. ***** Dataset contents ***** - ACESPACE_coarse_mode_aerosol_particle_size_distribution.csv, data file, comma-separated values - data_file_header.txt, metadata, text - README.md, metadata, text NaN values in a complete row denote missing values because of e.g., ship exhaust contamination, maintenance, instrument failure. NaN values which appear individually or only in small groups reflect that data were below detection limit. For latitude and longitude, NaN values are noted in cases where position data was not available for the given time period. ***** Dataset contact ***** Julia Schmale, Paul Scherrer Institute, Switzerland. ORCID: 0000-0002-1048-7962. julia.schmale@psi.ch ***** Dataset citation ***** Please cite this dataset as: Schmale, J., Henning, S., Tummon, F., Hartmann, M., Baccarini, A., Welti, A., Lehtipalo, K., Tatzelt, C., Landwehr, S. and Gysel-Beer, M. (2019). Coarse mode aerosol particle size distribution collected in the Southern Ocean in the austral summer of 2016/2017, during the Antarctic Circumnavigation Expedition. (Version 1.0) [Data set]. Zenodo. http://doi.org/10.5281/zenodo.2636709