Wind profiles from Galion Doppler lidar from the ARTofMELT expedition, Arctic Ocean 2023

Ian Brooks, Heather Guy

Profiles of wind speed and direction, and wind components, derived from a Galion G4000 Doppler Lidar installed on the roof of a shipping container on the foredeck of the Swedish icebreaker Oden.

The data were collected during the expedition ARTofMELT (Atmospheric Rivers and the Onset of Arctic Melt) in the Fram Strait pack ice during the spring transition, 10 May to 12 June, 2023.

Citation

Ian Brooks, Heather Guy (2025) Wind profiles from Galion Doppler lidar from the ARTofMELT expedition, Arctic Ocean 2023. Dataset version 1. Bolin Centre Database. https://doi.org/10.17043/oden-artofmelt-2023-wind-profiles-doppler-1

References

Edson JB, Hinton AA, Prada KE, Hare JE, Fairall CW (1998) Direct Covariance Flux Estimates from Mobile Platforms at Sea*. Journal of Atmospheric and Oceanic Technology 15:547–562.

Data description

Wind profiles are derived from Doppler velocity measurements from continuous VAD scans made at 20-degree intervals in azimuth and an elevation angle of 50 degrees. Data is provided as 2D arrays [time, height] at a resolution of approximately 102 s (1 minute 42 seconds) by 22.98 m. The full altitude range is 82 – 2311 m, but the effective maximum altitude of individual profiles depends on cloud conditions.

Wind speed and direction are derived from a sinusoidal fit to the raw along-beam Doppler velocities at each altitude using code from the Cloudnet suite (here the Matlab version, function ppi2windVAD). Wind variables provided are:

• wind speed
• wind direction
• wind components to East, North, and Up

Uncertainty estimates are provided for each output variable along with R-squared and the root mean squared error for each fit.

Data availability is limited by the presence of sufficient particles to provide the backscatter signal, which in the clean Arctic environment usually requires the presence of fog, cloud, or precipitation. There are thus significant gaps in the time series when particle concentrations are low and the signal to noise ratio too weak. Data is only available when SNR > -16 dB and all the lidar internal quality control checks are passed.

The measured along-beam Doppler velocities are individually corrected for platform motion and attitude prior to calculation of the mean wind profiles. The correction is small when the ship is moored to the ice floe, removing only the ice drift velocity, but can be both substantial and variable from beam to beam when the ship is under way and breaking ice. The corrections follow the same procedure used to correct turbulence measurements on ships, following Edson et al. (1998).

Primary variables

• time seconds since 00:00:00 01-01-1970 [time]
• doy Decimal day of year (in UTC) [time]
• year Year [time]
• month Month of the year [time]
• day Day of the month [time]
• hour Hour of the day (in UTC) [time]
• minute Minutes of the hour [time]
• second Seconds of the minute [time]
• height height above surface (m) [height]

Derived variables

• u eastward wind component (m/s) [time, height]
• v northward wind component (m/s) [time, height]
• w upward wind component (m/s) [time, height]
• windspeed horizontal wind speed (m/s) [time, height]
• winddirection direction wind is from (degrees from north) [time, height]
• u_error uncertainty in eastward wind component (m/s) [time, height]
• v_error uncertainty in northward wind component (m/s) [time, height]
• w_error uncertainty in upward wind component (m/s) [time, height]
• windspeed_error uncertainty in wind speed (m/s) [time, height]
• winddirection_error uncertainty in wind direction (degrees) [time, height]
• R_squared R-squared of sinusoidal fit [time, height]
• RMSE root mean square error in sinusoidal fit (m/s) [time, height]
• azavail number of azimuth angles used [time, height]

Comments

The Galion lidar was installed on top of a shipping container on the foredeck of the Oden, at a height of approximately 13m above the waterline and operated continuously throughout the cruise. An XSENS MTi-700-G motion sensor is attached to, and aligned with, the lidar. 10Hz data (3-axis rotation rates and acceleration) from the XSENS motion pack is combined with low rate (0.2 Hz) heading and horizontal velocity data from the ship navigation system to calculate a high-rate attitude (pitch, roll, heading) and 3-dimensional velocity components following Edson et al. (1998). These are used to correct the individual Doppler velocity measurements for the component of platform motion along-beam. Wind profiles are calculated from the motion-corrected Doppler velocities.

An assessment of the performance of the Galion G4000 can be found here.

Data creators

• Ian Brooks: principle investigator, operator, and data set creator
• Heather Guy: operator

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.