WAMOS (marine radar) data collected during the Antarctic Circumnavigation Expedition (ACE, https://spi-ace-expedition.ch/), from December 2016 to March 2017.

Waves in the Southern Ocean are the biggest on the planet. They exert extreme stresses on the coastline of the Sub-Antarctic Islands, which affects coastal morphology and the delicate natural environment that the coastline offers. In Antarctic waters, the sea ice cover reflects a large proportion of the wave energy, creating a complicated sea state close to the ice edge. The remaining proportion of the wave energy penetrates deep into the ice-covered ocean and breaks the ice into relatively small floes. Then, the waves herd the floes and cause them to collide and raft.

There is a lack of field data in the Sub-Antarctic and Antarctic Oceans. Thus, wave models are not well calibrated and perform poorly in these regions. Uncertainties relate to the difficulties to model the strong interactions between waves and currents (the Antarctic Circumpolar and tidal currents) and between waves and ice (reflected waves modify the incident field and ice floes affect transmission into the ice-covered ocean). Drawbacks in wave modelling undermine our understanding and ability to protect this delicate ocean and coastal environment.

By installing a Wave and Surface Current Monitoring System (WaMoS II, a marine X-Band radar) on the research vessel Akademic Thresnikov and using the meteo-station and GPS on-board, this project has produced a large database of winds, waves and surface currents. Dara were collected during the Antarctic Circmumnavigaion Expedition, which took place from Dec. 2016 to Mar. 2017. The instrumentation operated in any weather and visibility conditions, and at night, monitoring the ocean continuously over the entire Circumnavigation.

Records can support

1. the assessment of metocean conditions in the Southern Oceans; and

2. calibration and validation of wave and global circulation models.

Data - AAS_4434_ACE_WAMOS contains sea state conditions monitored continuously with a Wave and Surface Current Monitoring System (WaMoS II), a wave devise based on the marine X-Band radar (see Hessner, K. G., Nieto-Borge, J. C., and Bell, P. S., 2007, Nautical Radar Measurements in Europe: Applications of WaMoS II as a Sensor for Sea State, Current and Bathymetry. In V. Barale, and M. Gade, Sensing of the European Seas, pp. 435-446, Springer). Sea state consists of the directional wave energy spectrum, angular frequency and direction of propagation. Basic parameters such as the significant wave height (a representative measure of the average wave height), the dominant period, wavelength, mean wave direction, etc… were inferred from the wave spectrum. Surface current speed and the concurrent direction were also detected. Post processed data are available anytime the X-Band radar was operated in a range of 1.5NM; a full spectrum was generally obtained evert 20 minutes.

Data are subdivided in:

- WaMoS II frequency spectrum (1-D spectra)

- WaMoS II wave number spectrum (2-D spectra)

- WaMoS II frequency direction spectrum (2-D spectra)

Data are quality controlled.

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File informations

Path to the spectra: \RESULTS\YYYY\MM\DD\HH\ : Year, month, day, hour.

space\ : spatial mean results.

single\ : raw spectra.

mean\ : time averaged files.

Header of the spectra:

Additional information that might be needed for data analysis is stored in the headers.

The output results generated using different WaMoS II software modules are separated by comment lines starting with ‘CC’. All headers are subdivided into:

1) Polar Header: including data acquisition parameters.

2) Car Header: including Cartesian transformation parameters.

3) Wave-Current Analysis Header: including wave and current analysis related parameters.

There is a keyword of maximum 5 characters in each line of the header followed by some values and a comment, after the comment marker ‘CC’, describing the keyword.

Values of missing parameters are set to -9, -9.0, -99.0, etc. depending on the data type.

The 'end of header' keyword 'EOH', indicated the last line of the header section.

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WaMoS II frequency spectrum (1-D spectra):

File Name:

YYYY : Year.

MM : Month.

DD : Day.

HH : Hour.

MM : Minute.

SS : Second.

rigID : WaMoS II platform’s ID code (3 letters)

Suffix:

’*.D1S’ : spatial mean of the spectra (that pass the WaMoS II internal quality control) averaged over WaMoS II analysis areas (up to 9) placed within the radar field of view.

‘*.D1M’ : temporal average spectra calculated using all spectra collected during the past dt=30 minutes of the time specified in the file.

Time reference: CPU clock.

Data Content:

Frequency (f - Hz).

Spectral energy (S(f) - m*m/Hz).

Mean Wave Direction (MDIR(f) - deg), ���coming from’.

Directional Spreading (SPR(f) - deg/Hz).

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WaMoS II wave number spectrum (2-D spectra):

File Name:

YYYY : Year.

MM : Month.

DD : Day.

HH : Hour.

MM : Minute.

SS : Second.

rigID : WaMoS II platform’s ID code (3 letters)

Suffix:

’*.D2S’ : spatial mean of the spectra (that pass the WaMoS II internal quality control) averaged over WaMoS II analysis areas (up to 9) placed within the radar field of view.

‘*.D2M’ : temporal average spectra calculated using all spectra collected during the past dt=30 minutes of the time specified in the file.

Time reference: CPU clock.

Data Content:

Spectral energy (S(kx,ky) - m*m/(Hz*rad)) as a function of wave number (kx and ky - rad/m).

Data related header information

MATRIX: Size of Matrix.

DKX: Spectral resolution in Kx direction (2*Pi/m).

DKY: Spectral resolution in Ky direction (2*Pi/m).

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WaMoS II frequency direction spectrum (2-D spectra):

File Name:

YYYY : Year.

MM : Month.

DD : Day.

HH : Hour.

MM : Minute.

SS : Second.

rigID : WaMoS II platform’s ID code (3 letters)

Suffix:

‘*.FTH’ : spatial mean of the spectra (that pass the WaMoS II internal quality control) averaged over WaMoS II analysis areas (up to 9) placed within the radar field of view.

’*.FTM’ : temporal average spectra calculated using all spectra collected during the past dt=30 minutes of the time specified in the file.

Time reference: CPU clock.

Data Content:

Spectral energy (S(f,θ) - m*m/(Hz*rad)) as a function of frequency (f – Hz) and direction (θ - deg).

Data information

Mf : number of frequency sampling points.

Mth : number of direction sampling points.

Data Matrix: Row 1 frequency sampling points, Column 1 direction sampling points.

The dataset download also includes a file, "Available_Measurements", which is a general calendar that provides the list (day and time) of available measurements.