Abstract:

The dataset contains ADCP records from 5 deployments of a floating sediment trap during the ECOGIG-2 EN600 water-column cruise. The instrument was a downward-facing TRDI 300kHz Workhorse ADCP drifting at the surface and recording velocities down to ~100m. Data were collected from June 4 to June 19, 2017.

Suggested Citation:

Andreas Thurnherr. 2018. ADCP Data from a Floating Sediment Trap, Gulf of Mexico, June 4 to 19, 2017. Distributed by: Gulf of Mexico Research Initiative Information and Data Cooperative (GRIIDC), Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7639N9M

Purpose:

To provide measurements of the velocity field above the drifting sediment trap.

Data Parameters and Units:

Time, latitude (deployment, decimal degrees), longitude (deployment, decimal degrees), latitude 2 (recovery, decimal degrees), longitude 2 (recovery, decimal degrees), bin (bin number), dz (distance of bin center from transducer in meters), depth (water depth of bin center in meters, equal to dz), N_ensembles (total number of ensembles in PD0 file), first_ens (ensemble number of first valid record of this deployment), last_ens (ensemble number of final valid record of this deployment), pct_good_vels (percentage of all velocity samples in the PD0 file that are valid), pct_3_beam (percentage of all velocity samples in the PD0 file that are derived from 3 beams), mag_decl (correction for magnetic declination in degrees that was applied during processing), soundspeed_correction (salinity [psu], temperature [degrees Celsius] and depth [m] for soundspeed correction). Each time series contains the following data: ensemble ADCP record number, dn17 (2017 decimal day [0.5 indicates noon of Jan 1]), heading degrees), ADCP pitch (degrees from vertical), roll (Adegrees from vertical), temp (uncalibrated ADCP transducer temperature, degrees Celsius), u (eastward velocity component, m/s), v (northward velocity component, m/s), w (upward vertical velocity component, m/s), err_vel TRDI ADCP (error velocity, m/s), corr1 (correlation in beam 1, arbitrary units), corr2 (correlation in beam 2, arbitrary units), corr3 (correlation in beam 3, arbitrary units), corr4 (correlation in beam 4, arbitrary units), amp1 (echo amplitude [acoustic backscatter] in beam 1, arbitrary units), amp2 (echo amplitude in beam 2, arbitrary units), amp3 (echo amplitude in beam 3, arbitrary units), amp4 (echo amplitude in beam 4, arbitrary units). The archived data comprise bins 2-13 (20-110m below the surface); bin 1 is not included because zero blanking was used. Each data file contains a time series d (3s sampling interval) of one of the ADCP bins from a single deployment (002, 006, 008, 013 and 015) of the floating trap. The file names are constructed from the deployment and bin numbers. The file 008_2.nc contains the data from bin2 from the 3rd deployment. All data files from a deployment are combined into an archive named after the deployment (e.g. 002.tgz). All deployment archives are combined into a single file called PITTA_EN600_ADCP.tar. id deployment lon/lat recovery lon/lat --------------------------------------------------------------- 002 -96.3283, 26.7473 -96.4343, 26.7151 006 -91.9799, 27.4985 -92.2308, 27.5034 008 -91.4976, 27.7805 -91.4867, 27.9066 013 -90.0369, 27.2871 -89.8466, 27.156 015 -91.8216, 27.3513 -92.0585, 27.5304

Methods:

The following data processing steps were applied to each file: 1. Trim out-of-water records from beginning and end of file. 2. Rotate velocities into Earth-coordinate frame. 3. Apply magnetic declination correction of -2 degrees. 4. Apply soundspeed correction for water with salinity 36.4 and temperature 30 degrees Celsius to correct velocities and bin distances (dz)

Instruments:

TRDI 300kHz Workhorse Monitor ADCP

Error Analysis:

TRDI ADCPs have built-in screening of the velocity data, which was used with unmodified parameters. The velocities from all deployments were inspected and a basic analysis was carried out. No measurement anomalies were detected.

Individual Files: