Abstract:

Several hundred Consortium for Advanced Research on Transport of Hydrocarbon in the Environment (CARTHE) surface drifters were released during the Submesoscale Processes and Lagrangian Analysis on the Shelf (SPLASH) experiment in the Louisiana Bight from 2017-04-19 to 2017-06-08. The drifters were drogued at 0.5 m depth and reported their positions in real-time using SPOT GPS units nominally every 5 minutes for up to about 5 months. Some of the drifters were equipped with temperature and/or salinity sensors. This dataset contains the quality-controlled data, where positions suggesting excessive velocities (> 2.62 m/s) or accelerations (> 0.01 m/s^2) were removed. The positions were then interpolated using a Hermitian cubic algorithm to uniform 5-minute intervals. However, gaps exceeding three hours were not filled. Where available, temperature and salinity data from HOBO sensors were appended to the trajectories. A companion dataset with the raw data is available under GRIIDC Unique Dataset Identifiers (UDI) R4.x265.238:0001 (DOI: 10.7266/n7-wgt0-kw56).

Suggested Citation:

Helga Huntley, Guillaume Novelli, Andrew Poje, Philippe Miron, Ed Ryan. 2019. Submesoscale Processes and Lagrangian Analysis on the Shelf (SPLASH) surface drifter’s interpolated to 5-minute intervals data in the Louisiana Bight from 2017-04-19 to 2017-06-08. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-0pkg-hd54

Purpose:

The drifters were released to study submesoscale dispersion on the shelf.

Data Parameters and Units:

SPLASH_drifters_TS.dat: drifter ID string (S_XXXX, XXXX = 4-digit integer), Date/time (yyyy-mm-dd HH:MM, UTC), longitude and latitude (decimal degrees), temperature (degrees C; NaN if not available), salinity (psu; NaN if not available). splash_spot_drifter_launch_info.prn: drifter ID string (S_XXXX, XXXX = 4-digit integer), drifter type (drogued= standard drifters, undrogued = standard drifters but without drogue, temperature = standard drifters with temperature (HOBO) sensor, salinity= standard drifters with temperature + salinity (HOBO) sensors), launch date/time (yyyy-mm-dd HH:MM:SS, UTC), vessel (WS for Walton Smith; the others are small boats ARGUS, Alex, Arnoldo, CB for Calibou Boca, SAND_CRAB, TATIANA, UCLA, and WHISKEY_PASS), launch group (see ReadMe file for more information), launch node (see ReadMe file), longitude and latitude (decimal degrees), end date and time of the entire record deemed credible (yyyy-mm-dd HH:MM:SS). The launch coordinates and times were recorded with a hand-held GPS device at the time of launch and some of the coordinates may be missing. The dataset includes a readme file.

Methods:

The CARTHE-style drifters (drogued at 0.5 m), tracked in real-time using SPOT GPS units, were released in multiple groups, including several survey lines and multiple gridded arrays with various spacing, in the Louisiana Bight of the northern Gulf of Mexico in April-May 2017. Some of the drifters had temperature and/or salinity sensors attached. Many drifters (including those with sensors) were released and recaptured for repeated releases. The following processing was performed on the raw trajectory data: (1) Duplicate entries, out-of-range positions, and data before launch and after best guess end time were removed. (2) Positions implying velocities exceeding 2.62 m/s or accelerations exceeding 0.01 m/s^2 were removed. (3) Positions were interpolated to regular 5-minute intervals using a piecewise Hermitian cubic algorithm, but gaps exceeding 3 hours were retained. (4) Temperature and salinity measurements as obtained from HOBO sensors were interpolated (piecewise Hermitian cubic) to the same time sampled by the trajectories and appended to the trajectory data. Clearly non-sensical salinity and temperature data were deleted. Note also that some sensors failed, so that drifters of type “salinity” or “temperature” may not, in fact, have these data appended.

Individual Files: