***** Dataset title ***** Hydrometeor particle size distribution data collected using a snow particle counter on board the R/V Akademik Tryoshnikov in the Southern Ocean during the austral summer of 2016/17 as part of the Antarctic Circumnavigation Expedition (ACE). ***** Dataset abstract ***** The data consist of the hydrometeor particle size distribution for particles with a size range (average diameter) from 36 to 490 μm (with the last bin including all detected particles larger than 490 μm) detecting the flux of snow, rain and other particles including sea spray passing through a photo-electric snow particle counter (SPC-95) installed on board the R/V Akademik Tryoshnikov as part of the Antarctic Circumnavigation Expedition (ACE). Data were recorded from January to March 2017 in the Southern Ocean. Here we present the raw data set, generated by the SPC-95 Data Processing Device, which consists of the number of particles, classified into 64 size bins, passing through the snow particle counter with a time resolution of one second. Data are presented in daily files and have undergone some pre-processing. The data were collected as part of ACE project 18 aiming to estimate freshwater fluxes (particularly precipitation and blowing snow) and understand their contribution to surface freshening in the Southern Ocean. ***** Original data collection ***** In order to understand the uncertain freshwater fluxes from the atmosphere and their contribution to surface freshening in the Southern Ocean, particle flux measurements were taken (ACE project 18). A photo-electric snow particle counter (SPC-95, sensor code No.1105, manufactured by Niigata Electric; purchased/owned by EPFL, Switzerland) was installed on the railing on the upper deck of the R/V Akademik Tryoshnikov (about 30 m asl). The SPC was connected via a network cable to a data logger (Data Processing Device) which was situated in the communications room on deck four of the superstructure of the ship. The data were recorded on a CF Logger using a CF memory card. More information about the installation of the instrument as part of the ACE expedition can be found in the ACE Cruise Report (Walton and Thomas, 2018). The following technical information is based on SPC-95 Installation Guide, ver.0.30, by Niigata Electric Co., Ltd (Japan). SPC-95 measurement part consists of 1) Light projecting part (SLD – Super Luminiscent Diode) with collimator (lambda=830nm, which is near-infrared light) 2) light detecting part (has a slit of size 0.5x2mm, and collects the light beam by using the photo diode built inside the lens, with integrated pre-amplifier circuit); 3) Detection band of size 25x2x0.5mm (width, height, depth) measuring snow particles; 4) wind wheel and slip-ring – this part turns around when the wind speed is more than 5 m/s, in order to position the measuring surface area to cross the wind blowing direction; 5) temperature sensor (located next to the light projecting part). The measurement method is detecting the light reduction caused by snow particles passing through the parallel light beam. The measurement object is defined as a spherical shape. The data generated by SPC Data Processing device consists of snow particle size distribution for particles with a size range from 36 to 490 μm (average particle diameter), dividing the detected particles into 64 diameter classes at 7 μm bin resolution (except for the first two bins and the last bin, see data_file_header.txt)), with a time resolution of one second. If the average diameter of a detected particle is larger than 490 μm, the particle was assigned to the maximum diameter class. Particles smaller than 36 μm were undetected. The diameter and the number of blowing snow particles were detected by their shadows on a photodiode. Electric pulse signals of snow particles passing through a sampling volume (2 mm × 25 mm × 0.5 mm) were sent to an analyzing logger. The sampling area, perpendicular to the horizontal wind vector was 50 mm^2 (2 mm × 25 mm). The data were recorded continuously in .LOG files onto the data logger which contained a CF memory card, then downloaded every few days to a PC (Toughbook) using the CF-card reader with USB connection. The SPC recorded data during a total of 65 days divided in two periods: 1) during leg 1: between 8 and 18 January 2017; 2) during legs 2 and 3: between 23 January and 17 March 2017. For the description of SPC and examples of its application for blowing snow and precipitation detection see Leonard and Cullather (2011), Naaim-Bouvet et al (2014) and Nishimura et al (2014). Accompanying datasets were collected during the expedition within Project 18: total snow particle flux using Wenglors (with a 10-second resolution), snowflake casting using formvar technique, and vertical atmospheric profiles from radiosondes (https://doi.org/10.5281/zenodo.4382459). Basic meteorological parameters were recorded by the ship’s Vaisala MAWS system (https://doi.org/10.5281/zenodo.3360427). ***** Data processing ***** The binary data log files (eg, 000B.LOG) were converted to daily ASCII files using the SnowPCbin2ascii.exe programme for SPC-95 (version 2.0.15.0918beta; July 2015; developed and provided by Niigata Electric) running on a Windows PC (Toughbook). This program also detects and corrects any abnormal time/temperature data figures included in the data and creates 1-second data and 1-minute data. Data is exported as daily units. The beginning of each day is recorded as 00:00:01 (also in the data filename) and the end of the date is 00:00:00 on the next day. Some files start at another time (eg, U170110_190855Snow-1105-1sec-org-0006), which means the previous file contains an interrupted data stream for this day (eg, U170110_000001Snow-1105-1sec-org-0005 runs until 17:08:54). The CSV filename is composed as following: [U(UTC) or J(JST)] [YYDDMM and Time of data start]Snow-[Sensor Code]-1sec-org-[“LOG” filename].csv The SPC is equipped with a built-in GPS and detects its own time. Abnormal time detection rarely occurs. The SnowPCTimeChecker.exe programme allows for checking detections of abnormal temperature data or time changes (however this check was not applied to the ACE data). Following data collection, file names and file contents were corrected to show the correct sensor code. The following changes were made: - In the filenames, 04 was replaced by 1105, e.g. U170308_000001Snow-04-1sec-org-000E.csv is now U170308_000001Snow-1105-1sec-org-000E.csv - Within each file, the first parameter in each line (No.) was 04 for the sensor code. This was replaced with 1105. No further processing has been undertaken. ***** Quality checking ***** This raw dataset is published as is after pre-processing described above without any additional quality checking. ***** Standards ***** This dataset does not conform to any particular standards. ***** Further information for interpreting the data and using the dataset ***** Filters: No filters have been applied to SPC raw data as filtering depends on the application (precipitation, blowing snow, sea spray..). Thus some daily files contain spurious high peaks which have to be filtered when working with the data. Timescales: 1-second Interpolation: Data are already at high resolution (1-sec). Interpolation of missing values is not advised. Aggregation to lower temporal resolution: The original 1-second data can be averaged over lower temporal resolution (1-minute, 1-hour) keeping the units as # of particles per second (per size bin). ***** Dataset contents ***** - UYYMMDD_hhmmssSnow-***(Sensor code No.)-1sec-org-***(CF SerialNo).csv, data files, comma-separated values - data_file_header.txt, metadata, text - README.txt, metadata, text ***** Dataset contact ***** Irina Gorodetskaya, CESAM – Centre for Environmental and Marine Studies, Department of Physics, University of Aveiro, Portugal. ORCID: 0000-0002-2294-7823. Email: irina.gorodetskaya@ua.pt ***** Dataset license***** This pre-processed hydrometeor particle flux dataset from ACE is made available under the Creative Commons Attribution 4.0 International License (CC BY 4.0) whose full text can be found at https://creativecommons.org/licenses/by/4.0/ ***** Dataset citation ***** Please cite this dataset as: Gorodetskaya, I., Leonard, K., Tsukernik, M. and Lehning, M. (2021). Hydrometeor particle size distribution data collected using a snow particle counter on board the R/V Akademik Tryoshnikov in the Southern Ocean during the austral summer of 2016/17 as part of the Antarctic Circumnavigation Expedition (ACE). (Version 1.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.4446616