John Prytherch, Ian Brooks, Heather Guy, Michail Karalis, 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 ARTofMELT (Atmospheric Rivers and the Onset of Arctic Melt) in the Fram Strait pack ice during the spring transition, 8 May to 14 June of 2023. The dataset covers measurements from 6 May to 12 June, 2023.
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Citation
John Prytherch, Ian Brooks, Heather Guy, Michail Karalis, Sonja Murto, Michael Tjernström (2024) Micrometeorological data from icebreaker Oden’s foremast during expedition ARTofMELT, Arctic Ocean, 2023. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-artofmelt-2023-micromet-oden-1
References
Sonja Murto, Michael Tjernström, Michail Karalis, John Prytherch (2024) Wind, temperature, relative humidity, surface temperature and radiation from expedition ARTofMELT, Arctic Ocean, 2023. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-artofmelt-2023-weather-station-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 7.1 MB (compressed 4.2 MB).
A list of all variable names, with short explanations and units is provided below. There is also an associated Readme_foremast.txt file that provides 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:
- 1 min time averaged data
- 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 = not used, 1 = good data and 2 = suspect 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 maneuvering or errors detected by sensor diagnostics.
Detailed lists:
- Time
day_of_year Decimal day of year (in UTC; Jan 1 = 1) [time]year Year [time]month Month [time]day Day [time]hour Hour [time]minute Minute [time]second Second [time]
- Wind variables corrected for ship motion and flow distortion
wind_speed True vector averaged wind speed (m s-1) [time]wind_from_direction True averaged wind direction (deg) [time]eastward_wind West-east averaged wind component (U) of the true wind (m s-1) [time]northward_wind South-north averaged wind component (V) of the true wind (m s-1) [time]wind_speed_relative Wind speed relative to the ship (m s-1) [time]wind_direction_relative Wind direction relative to the ship (deg; 0 deg = bow on) [time]wind_speed_10m Calculated 10-meter wind speed using logarithmic profile and k = 0.4 (m s-1) [time]wind_speed_10m_relative Calculated 10-meter wind speed relative to ship using logarithmic profile and k = 0.4 (m s-1) [time]
- Thermodynamic state variables
air_pressure Atmospheric pressure at the mast instrumentation (20.3m), adjusted from 7th deck SHIP sensors (hPa) [time]surface_air_pressure Atmospheric pressure at sea surface (hPa) adjusted from 7th deck SHIP sensors (hPa) [time]sonic_air_temperature Sonic temperature from speed-of-sound (K) [time]sonic_air_temperature_derived Air temperature from sonic speed-of-sound and specific humidity (K) [time]air_temperature Mean air temperature from the 7th deck SHIP sensors (K) [time]surface_temperature Surface air temperature (approximated from SHIP sensors as air temperature + 1) (K) [time]relative_humidity Mean relative humidity from 7th deck SHIP sensors (%) [time]relative_humidity_licor Relative humidity from the LI-7500 instrument (%) [time]relative_humidity_wrt_ice Relative humidity (at mast height) with respect to ice (%) [time]specific_humidity Specific humidity (kg kg-1) [time]surface_specific_humidity Specific humidity at surface estimated from surface temperature assuming RH = 98 % (kg kg-1) [time]humidity_mixing_ratio Water vapor mixing ratio (kg kg-1) [time]moist_air_density Density of moist air at current conditions (kg m-3) [time] dry_air_density Density of dry air at current conditions (kg m-3) [time]specific_heat_capacity_of_moist_air Specific heat capacity of moist air at current conditions (J kg-1 K-1) [time]latent_heat_of_vaporisation Latent heat vaporisation at surface temperature (J kg-1) [time]sea_ice_area_fraction Sea-ice concentration interpolated from AMSR2 ASI (%) [time]
- Surface turbulent fluxes positive upwards
kinematic_momentum_flux_u Kinematic eddy covariance along-wind momentum flux (m2 s-2) [time]kinematic_momentum_flux_v Kinematic eddy covariance across-wind momentum flux (m2 s-2) [time]friction_velocity_u Friction velocity (u*) derived from the eddy covariance along-wind momentum flux (m s-1) [time]friction_velocity_uv Total friction velocity (u*) using both along- and across-wind momentum flux (m s-1) [time] surface_upward_sensible_heat_flux_licor Sensible heat flux from sonic temperature corrected by LI-7500 humidity (W m-2) [time]surface_upward_sensible_heat_flux_met Sensible heat flux from sonic temperature corrected by SHIPS humidity (W m-2) [time] upward_sonic_temperature_heat_flux Sensible heat flux from uncorrected sonic temperature (W m-2) [time]surface_upward_sensible_heat_flux_bulk Sensible heat flux calculated by bulk method (following Smith 1988) (W m-2) [time]surface_upward_latent_heat_flux_vapor Latent heat flux from LI-7500 using calculated latent heat of vaporisation (W m-2) [time]surface_upward_latent_heat_flux_subl Latent heat flux from LI-7500 using constant (2.834E6) latent heat of sublimation (W m-2) [time] surface_upward_latent_heat_flux_bulk Latent heat flux calculated with bulk method (following Smith 1988) (W m-2) [time]
- Boundary layer stability parameters
stability_parameter Dimensionless stability parameter z/L; z is measurement height and L Obukhov length (-). Positive = stable [time]stability_parameter_10m Dimensionless stability parameter z/L; z is 10 meter and L Obukhov length (-). Positive = stable [time] neutral_wind_speed_10m Calculated 10-meter wind speed assuming neutral stratification (Businger-Dyer stability corrections) (m s-1) [time]neutral_wind_speed_10m_relative Calculated 10-meter relative wind speed assuming neutral stratification (Businger-Dyer stability corrections) (m s-1) [time]neutral_air_temperature_10m Calculated 10-meter temperature assuming neutral stratification (Businger-Dyer stability corrections) (K) [time]neutral_air_virtual_temperature_10m Calculated 10-meter virtual temperature assuming neutral stratification (Businger-Dyer stability corrections) (K) [time] neutral_specific_humidity_10m Calculated 10-meter specific humidity assuming neutral stratification (Businger-Dyer stability corrections) (kg kg-1) [time]
- Data quality flags
qc_flag_all_foremast_variables This flag is valid for all variables measured with the sensors on the foredeck mast, 1- and 20-minute data [time]qc_flag_momentum_flux_u Data quality flag for kinematic momentum flux and derived variables, for when only the along-wind component is used [time]qc_flag_momentum_flux_uv Data quality flag for kinematic momentum flux and derived variables, for when bot along- and across-wind components are used [time]qc_flag_sensible_heat_flux_licor Data quality flag for sensible heat flux, when sonic temperature is corrected using Licor humidity [time]qc_flag_sensible_heat_flux_met Data quality flag for sensible heat flux, when sonic temperature is corrected using SHIPS humidity [time] qc_flag_latent_heat_flux Data quality flag for latent heat flux [time]
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)
A Rotronic aspirated TRH sensor was also located on the foremast, but due to its malfunctioning fan for the majority of the expedition, this data is excluded from this dataset. However, corrected datasets for the mast relative humidity and temperature can be found in the weather station dataset, which is also found as another dataset on the Bolin Centre Database, by Murto et al. 2024. Therefore, in this version of the dataset, some meteorological variables, such as temperature, surface temperature, relative humidity and pressure, are estimated from continuous measurements from the ship's standard sensors. This likely has little impact, but may be updated in later versions.
Quality control
Quite some 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 very complex and tedious 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)
- Ian Brooks (operator, WP leader)
- Michail Karalis (operator)
- Michael Tjernström (operator, chief scientist)
The expedition
Data were collected during the ARTofMELT 2023 expedition on board the Swedish icebreaker Oden, which was organized by the Swedish Polar Research Secretariat from 8 May through 14 June, 2023.