Surface cyclone mask for the Antarctic Circumnavigation Expedition from December 2016 – March 2017.

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

This dataset contains a surface cyclone mask, which records the presence of a surface cyclone along the track of the Antarctic Circumnavigation expedition (ACE). The surface cyclones are calculated applying a 2D cyclone identification algorithm (Wernli and Schwierz, 2006; Sprenger et al., 2017) using global operational analysis data of the European Centre for Medium Range Weather Forecasts. 

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

The surface cyclone mask records the presence of a surface cyclone at the ship’s position along the ACE track. A 2D cyclone identification algorithm was applied to identify surface cyclones by the outermost closed sea level pressure contour around a pressure minimum (Wernli and Schwierz, 2006; Sprenger et al., 2017) using the six-hourly global operational analysis data of the European Centre for Medium Range Weather Forecasts (ECMWF) and short-term forecasts in between the analysis time steps at 03:00, 09:00, 15:00 and 21:00 UTC. The ECMWF fields were interpolated on 137 vertical levels on a regular horizontal grid of 0.5 degree horizontal spacing. The surface cyclone fields were linearly interpolated in time and space along the 1-hourly ACE ship track (Thomas and Pina Estany, 2019; doi: 10.5281/zenodo.3483164) to generate a surface cyclone mask, where 0 denotes the absence and 1 the presence of a surface cyclone along the ACE track.

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

The surface cyclone mask denotes time periods when a surface cyclone passes the ACE ship track. During the passage of an extratropical cyclone, enhanced wind speed and high variability in surface pressure, air temperature and specific humidity as well as precipitation is expected. The actual environmental changes due to the passage of an extratropical cyclone depends on the position relative to the cyclone center and the cyclone’s fronts.

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

Timescales: The passage of a cyclone along the ACE track takes place within a few hours up to 2 days. The longest cyclone passages occurred close to Antarctica or if the ACE ship track followed the cyclone track.

Interpolation: The resolution of this data can be artificially increased up to seconds, but one needs to be aware that the ECMWF fields have a three-hourly resolution. Therefore, changes in the mask within 3 hours are caused by the spatial movement of the ship along the ACE track.

Aggregation to lower temporal resolution: The data can be aggregate up to 6 hours. An aggregation to lower resolution will not adequately represent the cyclone occurrence for most applications as the passage of the surface cyclone often occurs within a few hours up to two days and the recurrence frequency is approximately 1-3 days.

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

- cyclone_mask_1h.csv, data file, comma-separated values
- data_file_header.txt, metadata, text
- README.txt, metadata, text

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

Iris Thurnherr, Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland. ORCID: 0000-0003-3647-0373. Email: iris.thurnherr@env.ethz.ch Telephone: +41 44 632 82 66

***** Dataset license *****

This surface cyclone mask 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 *****

Thurnherr, I. and Wernli, H. (2020). Surface cyclone mask for the Antarctic Circumnavigation Expedition from December 2016 – March 2017. (Version 1.0) [Data set]. Zenodo. doi: 10.5281/zenodo.3974312