Abstract:
This dataset contains along-track meteorological and water surface elevation measurements made on board the R/V F.G. Walton Smith cruise WS17107 from 2017-04-17 to 2017-04-29 as part of the SPLASH experiment during April-May 2017 in the Louisiana Bight. The meteorological flux measurements were made from twin masts mounted on the bow of the R/V Walton Smith and water surface elevation measurements made from an array of Ultrasonic Distance Meters. Some of the parameters reported in this dataset include speed over ground, vessel heading, air temperature and pressure, relative humidity, wind speed and direction, wind stress, significative wave height, and friction velocity. Additional information for R/V F.G. Walton Smith cruise WS17107 can be found in the R2R repository: https://www.rvdata.us/search/cruise/WS17107. This cruise was led by chief scientist Dr. Brian Haus.
Suggested Citation:
Brian Haus. 2019. Underway meteorological observations collected during the SPLASH experiment aboard R/V F.G. Walton Smith cruise WS17107 in the Gulf of Mexico from 2017-04-17 to 2017-04-29. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-y1ar-0t35
Data Parameters and Units:
The data table provided is an M x N array where M is the number of time stamps and N is the total number of parameters outputted for each time stamp. Numerical GMT time (UTC days since January 0, 0000), latitude (decimal degrees), longitude (decimal degrees), northward speed over ground (SOG, m/s), eastward SOG (m/s), vessel heading (degrees, true clockwise (CW) from North), bow freeboard (m), air temperature (degrees C), relative humidity (%), air pressure (mb), heading relative to wind direction flag (unitless), mean wind speed (U) at anemometer (m/s), mean wind direction (degrees true clockwise from North), air density (kg/m3), COARE 3.5 wind speed at 10m (U10, m/s), COARE 3.5 wind friction velocity (Ust, m/s), COARE 3.5 drag coefficient (CD, arbitrary units), wind velocity at 10m height from eddy-correlation method (EC U10, m/s), wind friction velocity from eddy-correlation method (EC Ust, m/s), wind drag coefficient from eddy-correlation method (EC Cd, arbitrary units), along-stream wind stress (tau_x, N/m^2, positive is down), across-stream wind stress (tau_y, N/m^2, positive is right), stability parameter (zeta, dimensionless length), Monin-Obhukov length (MO Length, m), COARE 3.5 temperature at 10 m (T10, degrees C), COARE 3.5 specific humidity at 10 m (Q10m, g/kg), COARE 3.5 relative humidity at 10 m (RH10m, %), Ultrasonic Distance Meter (UDM) significant wave height (Hs) for 6 instruments (UDM1- UDM6, m). Anemometers were labeled 1.1, 1.2, 1.3 from top to bottom.
Methods:
All of the data were processed using a 10-minute averaging interval (for means, fluxes, significant wave height, etc.). Each 10-minute segment was passed through several quality control measures and represents data that: did not experience a change in heading > 40 degrees during the 10 minutes, did not observe wind coming from the aft quadrants of the ship, and did not experience any data interruptions longer than 30 seconds. All raw data was sampled at 20 Hz and then subsampled to 16 Hz for processing. All winds have been motion corrected and adjusted to account for vessel translation. Before motion correction, all data were passed through a despiking routine to remove outlier data. The heading relative to wind direction flag is defined as either 0, 1, or 2. 0 indicates that the wind is coming from within 20 degrees of the vessel heading. 1 indicates the wind is coming from the starboard quarter out to 90 degrees off the starboard beam. 2 indicates the same, but for the port side of the vessel. The meteorological masts were mounted on the starboard and port prows on the bow of the R/V Walton Smith (a SWATH vessel). Each mast was equipped with a vertical profile of anemometers. The port tower is #1 and the starboard tower is #2. The anemometers are coded from bottom to top of the profile 1-3. The 1 and 2 anemometers on both towers were RM Young 3D sonic anemometers. The 3 anemometers on each tower were Campbell Scientific IRGASONs. The UDMs were arranged with one sensor on each prow, and then 3 sensors arranged in a triplet configuration on a centerline truss mounted in between the two prows and extending ~1 m forward of the furthest edge of the prows. 6-degree vessel motion was acquired from a motion pack fastened to a bench in the R/V Walton Smith scientific lab. A GPS and magnetometer (1 Hz) were also deployed and used for all of the data processing. All systems were synced using a local NTP server.|Raw data sampled at 20 Hz, processed data was subsampled to 16 Hz, and then averaged over 10 minutes. The minimum spacing between successive time stamps in the data set is 10 minutes.
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