John Prytherch, Sonja Murto, Michael Tjernström
Air-sea fluxes and other micrometeorological variables are derived from fast response (20 Hz) measurements of the 3-dimensional wind vector, temperature and humidity using eddy covariance. The fluxes are direct representations of the air-sea exchange of momentum, sensible and latent heat and are derived using 20-minute averaging. Some other meteorological measurements and other supporting variables are also included.
The measurements are from the top of Oden's foredeck mast at ~20 m above sea level, during the expedition SAS (Synoptic Arctic Survey) covering a large area including parts of Amundsen Basin, Nansen Basin, the North Pole, Lomonosov Ridge, Morris Jesup Rise and the Yermak Plateau. Measurements ran continuously between July 27 and September 14, 2021.
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Citation
John Prytherch, Sonja Murto, Michael Tjernström (2025) Micrometeorological data from icebreaker Oden’s foremast during expedition SAS, Arctic Ocean, 2021. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-sas-2021-micromet-oden-1
Data description
The dataset includes two NetCDF (.nc) data files, one with 1-minute averaged meteorology and supporting variables and one with these same variables averaged over 20 minutes along with the eddy covariance flux estimates with this averaging time. The total size is 16.2 MB (compressed 11.5 MB).
A summarised list of variables is provided below. There is an associated readme_ACAS_SAS_foremast_v1.0.rtf file that provides variable names, units, further details of data and processing and explanations of quality control flags.
Dimensions
The dimension for the fields is time.
The two NetCDF files have the following different time resolutions:
ACAS_SAS2021_mast_1min_v1_0.nc: 1 min time averaged dataACAS_SAS2021_mast_20min_v1_0.nc: 20 min time averaged data
Variables
Divided into:
Wind variables
- measured wind speed and direction relative to the ship as well
- derived true winds in different configurations and calculated near-surface 10-meter winds
Thermodynamic state variables
- temperatures and relative humidity from different sensors
- atmospheric pressure, density and heat capacity
Surface turbulent fluxes (20-minute file only)
- direct eddy covariance estimates of momentum, sensible and latent heat fluxes, positive upwards
- boundary layer stability parameters
Quality control flag variables
Flag meanings: 0 = suspect data, 1 = good data. Suspect data refers to bad or missing data, which can be due to e.g., bad wind directions (|relative wind direction| >150 degrees from bow on), mast maintenance work, ship manoeuvring or errors detected by sensor diagnostics.
Comments
Measurement system
The data was obtained from Oden's foredeck mast with multiple sensors:
- Metec uSonic-3 sonic anemometer (3D winds and temperature; surface fluxes)
- Licor LI-7500 gas analyser (water vapour; surface heat fluxes)
- XSENS MTi-G-700 motion pack (platform motion corrections)
- Rotronic aspirated TRH sensor (temperature, humidity)
Quality control
Complex data corrections and quality control has been applied, e.g.,:
- corrections for ships motion
- correction for flow distortion using lookup table from CFD caluclations
- QC for mast maintenance work
- QC for bad wind directions (|relative wind direction| > 150 degrees from bow on)
- sensor specific diagnostics (e.g., Licor LI-7500 and Metek QC signal)
- flux specific statistical tests (for all surface fluxes)
Associated raw data and code
The derivation of turbulent fluxes from eddy covariance onboard a moving ship is a complex process. This is done in several steps, working from several sets of primary datasets additionally using special navigation and ships motion data. Therefore, the raw data for this dataset is not openly available and no processing code is published. Users are most welcome to contact the data creator for details on how this is done.
Data creators' roles
The instrument system was continuously logging and was monitored by the Stockholm University Meteorology team onboard Oden:
- John Prytherch (instrument responsible, dataset creator)
- Sonja Murto (operator)
- Michael Tjernström (PI)
The expedition
The data were collected in summer 2021 from Swedish icebreaker Oden during the Synoptic Arctic Survey (SAS) 2021 expedition organized by the Swedish Polar Research Secretariat.