***** Dataset title *****

Ice Nucleating Particle number concentration from low-volume sampling over the Southern Ocean during the austral summer of 2016/2017 on board the Antarctic Circumnavigation Expedition (ACE).

***** Dataset abstract *****

Ice nucleating particles (INP) are a subclass of atmospheric aerosol particles, which can force heterogeneous freezing of cloud droplets at temperatures above -38 degrees C. In contrast, ice particles form from cloud droplets at temperatures below -38 degrees C due to homogeneous freezing, without INP. Due to their abundance, these particles can affect micro-physical properties of clouds, while acting as INP. During the Antarctic Circumnavigation Expedition (ACE) around the Southern Ocean, off-line filter sampling was performed. Filters were stored on the ship and analysed after the cruise at Leibniz-Institute for Tropospheric Research (TROPOS) concerning INP abundance. Here, we give INP number concentrations for sampling of 8 hour periods.

***** Original data collection *****

A DIGITEL sampler with automatic filter exchange (type DPA-14 by Walter Riemer Messtechnik, Germany) was operated on the deck above the bridge of the R/V Akademik Tryoshnikov during ACE. On a PM10-inlet, the instrument was run on a flow rate of approximately 25 litres per minute. Polycarbonate membrane filters (type Nuclepore by Whatman, USA) with 200 nanometre pore-size were used solely, sampled for 8 hour periods.

Sampled filters were stored at -20 degrees C during the cruise and brought back to TROPOS, for further analysis, concerning INP abundance. For this, the Ice Nucleating Droplet Array (INDA) was used. In the process, filters were washed of using seven (10 in later stages of the analysis) millilitres of ultra-pure water (milliQ, 18.2 megohms per centimetre squared). The resulting solution was put in a PCR (polymerase chain reaction) tray, as 96 droplets, 1 micro-litre each. This tray was put into the ethanol bath of INDA, where droplet freezing behaviour was investigated by looking at how many compartments of the PCR tray are frozen, at a given temperature. In a later step, obtained temperature-profiles of the ratio between frozen and un-frozen compartments were used to derive the INP number concentrations. Further information on INDA and the derivation can be found in the supporting information in Hartmann et al. (2019).

The output of the INDA setup was stored digitally as a data table (ASCII format).

***** Data processing *****

The results of the INDA measurements for each filter were used in conjunction with information on volume of air sampled by the sampler and volume of milliQ water used to wash sampled material off the filter. The volume of sampled air is obtained from the output file of the sampler and contains normalized volume to standard conditions of 20 degrees C and 1000 hPa. The complete formula for INP concentration derivation can be found in the supporting information in Hartmann et al. (2019).

Analogous to sampled filters, INDA measurements were performed on field blank filters (FBF). An average frozen fraction profile for the FBFs was derived and is given as part of the dataset.

The data table was finalised using an interactive Python (version 2.7) with Ipython (version 5.4.1) on an Ubuntu operating system (version 16.04).

***** Quality checking *****

Recommendations on sample handling and processing given in Polen et al. (2018) were followed.

***** Standards *****
 
Wherever possible, these parameter names conform to the CF standard names (version 72) https://cfconventions.org/Data/cf-standard-names/72/build/cf-standard-name-table.html

***** Further information for interpreting the data and using the dataset *****

Interpolation: As sampling was performed for eight hours, interpolation to any finer resolution should be avoided.

***** Dataset contents *****

-ACESPACE_ice_nucleating_particles_number_concentration_from_lowvolume_filters.csv, data file, comma-separated values
- ACESPACE_ice_nucleating_particles_frozen_fraction_from_lowvolume_filters.csv, data file, comma-separated values
- data_file_header_frozen_fraction.txt, metadata, text
- data_file_header_number_concentration.txt, metadata, text
- README.txt, metadata, text
- change_log.txt, metadata, text

The files listed above contain Ice Nucleating Particles (INP) number concentration (N_INP) and frozen fraction (f_ice) values for the Antarctic Circumnavigation Expedition from off-line filter sampling. Both files contain values for temperatures from -5 to -30 degrees C in steps of 1K. In addition, an averaged f_ice and N_INP for the field blank filters (FBF) is given in the respective f_ice and N_INP file.

Additionally, longitude and latitude for the ship’s position at the start time of the averaging period are given.

For latitude and longitude NaN values are given, in cases where positioning data was not available for the given time period. There are no NaN values for frozen fraction included. For N_INP, NaN values indicate that concentrations are outside the detectable range of the method used.

***** Dataset contact *****

Christian Tatzelt, Leibniz Institute for Tropospheric Research, Germany. ORCID 0000-0001-7795-5372. Email: christian.tatzelt@tropos.de 
Silvia Henning, Leibniz Institute for Tropospheric Research, Germany. ORCID 0000-0001-9267-7825. Email: silvia.henning@tropos.de 

***** Dataset citation *****

Please cite this dataset as: 
Tatzelt, C., Henning, S., Tummon, F., Hartmann, M., Baccarini, A., Welti, A., Lehtipalo, K. and Schmale, J. (2020). Ice Nucleating Particle number concentration from low-volume sampling over the Southern Ocean during the austral summer of 2016/2017 on board the Antarctic Circumnavigation Expedition (ACE). (Version 1.1) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.4311665