***** Dataset title ***** Atmospheric profiling data collected from radiosondes in the Southern Ocean in the austral summer of 2016/2017 during the Antarctic Circumnavigation Expedition. ***** Dataset abstract ***** The data set consists of the vertical profiles of the atmospheric variables measured using radiosondes (i-Met) during the Antarctic Circumnavigation Expedition from November 2016 to April 2017. The data include the raw variables measured directly by the radiosondes and derived parameters: altitude (km), air pressure (mb), air temperature (deg C), relative humidity (%), frostpoint (deg C), potential temperature (deg K), water vapour mixing ratio (ppmv), total column water (mm w.e.), wind speed (m/s) and wind direction (deg). ***** Original data collection ***** Data were collected using iMet-1 radiosondes sending signals to the receiving ground station. The radiosondes were attached to a KAYMONT 200 g balloon filled with helium and were released from the rear deck of the R/V Akademik Tryoshnikov during the circumnavigation of Antarctica, as well as during the ship’s transit to and from Europe through the Atlantic Ocean, before and after the main part of the expedition around Antarctica. Most of the launches ascended up to 20-25 km height with an average speed of 5 m/s and also a horizontal displacement depending on the horizontal wind speed (see trajectory in file aceNNN_yyyymmdd.kml). Ground equipment:The radiosonde signal was received by an unidirectional antenna (PROCOM CXL 70-3LW/s from Meteolabor, Switzerland), connected to an AOR AR8600DX wide band receiver. Launches are described in more detail in the ACE cruise report (Walton and Thomas, 2018). Two different types of radiosondes were used: iMet-1-Abx and iMet-1-RSB 403 MHz GPS Radiosonde types. Both are meteorological radiosondes designed to transmit upper air pressure, temperature, humidity, and GPS data on the 403 MHz meteorological frequency once per second. Sensor details: thin polymer capacitive humidity sensor (range 0-100% RH, accuracy 5% RH, res < 0.1% RH, response time 2 s at 25 deg C; 60s at -35 deg C), bead thermistor temperature sensor (accuracy 0.2 deg C, res <0.01 deg, response time 2s at 1000 hPa), solid state piezoresistive pressure sensor (accuracy 0.5 hPa, resolution <0.01hPa, response time < 1s), 12 channel C/A Code GPS. The radiosondes are powered by alkaline dry cell batteries. Sampling rate is 1Hz. The sensors are installed inside an expanded polystyrene case. Information about the overall performance of i-Met-1 radiosonde sensors in comparison to other radiosondes can be found in Hurst et al. (2011). The GRUAN (GCOS reference upper-air system) comparison information for i-Met-1 at several stations is available at https://www.gruan.org/instruments/radiosondes/sonde-models/intermet-imet-1. The radiosonde of type iMet-1-ABx has a standard set of sensors without the possibility of adding extra ones. A total of 89 ABx radiosondes were launched during ACE of which 80 were successful (see overview_radiosonde_launches.csv). The radiosonde of type iMet-1-RSB is destined for extended research use as it allows additional sensors to be attached via the XDATA UART cables and connectors. iMet-1-RSB also includes a solid state pressure sensor. This radiosonde type has the same standard sensors as the iMet-1-Abx. Additional sensors connected during ACE included a supercooled liquid water content (SLWC) sensor from Anasphere. SLWC is a vibrating-wire sensor to determine supercooled liquid water content aloft using a principle of the change in natural frequency of a wire due to ice accretion along the wire (King et al 2016). SWLC sensor raw measurements are included in the general aceNNN_yyyymmdd.csv data file and consist of SLWC Frequency [Hz] and SLWC Board Temperature [deg C]. At total of 11 RSB radiosondes, equipped with an SLWC sensor, were launched during ACE of which 10 were successful (see overview_radiosonde_launches.csv): 1) ace041,25-01-2017,22:48:28, 2) ace048,30-01-2017,23:10:52 3) ace050,31-01-2017,22:51:30 4) ace052,02-02-2017,10:34:29 5) ace054,05-02-2017,01:40:51 6) ace059,09-02-2017,22:52:55 7) ace071,15-02-2017,10:57:33 8) ace078,19-02-2017,13:42:32 9) ace085,01-03-2017,20:52:41 10) ace087,03-03-2017,15:49:30 (launch partly successful) 11) ace088,04-03-2017,17:00:19 For several unsuccessful launches (ace006_20161223, ace034_20170114, ace038_20170123, ace078_20170219, ace099_20170316, ace100_20170316, ace101_20170318) no aceNNNflt.dat file is available. Data were received and stored directly on a computer using a Microsoft Windows 7 operating system and produced by the SkySonde software, telemetry and data analysis software written by Allen Jordan and Jim Wendell, NOAA (SkySonde Client Version 1.1.8.6; the SkySonde software is freely available from: https://www.esrl.noaa.gov/gmd/ozwv/wvap/sw.html). Data are presented in one folder per radiosonde launch named in the format aceNNN_yyyymmdd where NNN is the launch number, yyyy is the year, mm is the month and dd is the day. Dates and times are in UTC. Within each directory are raw and pre-processed data, with launch metadata, in the files as follows: - aceNNN_yyyymmdd.csv - main flight data file; - aceNNN_yyyymmdd.raw - file containing raw packet bytes (with timestamps) that is used for reprocessing the data; - aceNNN_yyyymmdd.raw_config - set of configuration options entered for the flight, used in conjunction with the RAW file for reprocessing; - aceNNN.de1 - NOAA/GMD flight description file; - aceNNNflt.dat - extended NOAA/GMD preliminary in-flight data; - aceNNNpre.dat - extended NOAA/GMD preliminary pre-flight data; - aceNNN_yyyymmdd.kml - Google Earth file containing the 3D balloon trajectory; - Sounding_ACENNN.png - plot of raw data. For a quick visualization of the measured profiles, plots of raw data (without quality checking) are provided showing measured changes in variables with pressure/height: (left) air temperature (solid black, bold) and dew point temperature (dash blue, bold) on a skew-T diagram; (right) relative humidity (RH) and wind speed. ***** Data processing ***** Pre-processing was also undertaken using the SkySonde Server software version 1.0.2.1 from NOAA/GMD (https://www.esrl.noaa.gov/gmd/ozwv/wvap/sw.html, last accessed on 08/07/2020). The pre-processing includes the translation of the received radio signal into the measured quantities and the calculation of derived quantities such as e.g. total column water and wind speed. A solar radiation correction was done for ace001 - ace009 during post-processing and therefore Temp and Traw differ for these launches. For all later launches, this correction was not applied. For consistency, Traw should be used for all launches. No calibration of the data has been done. For a possible post-processing, the operational meteorological measurements could be used (Landwehr et al., 2019). ***** Quality checking ***** Raw data are published without quality checking. Flagging has been applied only to denote successful or partially successful files. ***** Further information for interpreting the data and using the dataset ***** Timescales: The radiosonde dataset can be used to study phenomena on timescale from small-scale turbulence to large-scale advection. Interpolation: An interpolation of the data is not recommended except for the high frequency launches during specific events, because every radiosonde records the specific vertical structure during its launch. ***** Dataset contents ***** - aceNNN_yyyymmdd, directory -- aceNNN_yyyymmdd.csv, data file, comma-separated values -- aceNNN_yyyymmdd.kml, metadata, XML -- aceNNN_yyyymmdd.raw, data file, raw, ASCII DOS -- aceNNN_yyyymmdd.raw_config, metadata, XML -- aceNNN.de1, metadata, ASCII text format -- aceNNNflt.dat, data file, ASCII text format -- aceNNNpre.dat, data file, ASCII text format - Sounding_ACENNN.png, metadata, portable network graphics - data_file_header_csv.txt, metadata, text format - data_file_header_dat.txt, metadata, text format - data_file_header_launches.txt, metadata, text format - README.txt, metadata, text format - overview_radiosonde_launches.csv, metadata, comma-separated value where NNN is the launch number yyyy is the year, mm is the month and dd is the day. Dates are in UTC. ***** Dataset contact ***** Irina Gorodetskaya, Centre for Marine and Environmental Studies, University of Aveiro, Portugal. ORCID: 0000-0002-2294-7823. Email: irina.gorodetskaya@ua.pt Iris Thurnherr, Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland. ORCID: 0000-0003-3647-0373. Email: iris.thurnherr@env.ethz.ch ***** Dataset license ***** This radiosonde 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.V., Thurnherr, I., Tsukernik, M., Graf, P., Aemisegger, F., Wernli, H. and Ralph, F.M. (2021). Atmospheric profiling data collected from radiosondes in the Southern Ocean in the austral summer of 2016/2017 during the Antarctic Circumnavigation Expedition. (Version 1.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.4382460