Abstract:

This dataset reports near-surface currents and sea surface roughness derived from X-band radar aboard R/V Walton Smith cruise WS17107 near the Taylor Energy oil leak site, Gulf of Mexico from 2017-04-19 to 2017-04-21. This data was collected during the CARTHE II sponsored Submesoscale Processes and LAgrangian Analysis on the SHelf (SPLASH) experiment in the northern Gulf of Mexico. It was obtained from a coherent-on-receive marine X-band (9.5 GHz) radar (Braun et al., 2008), developed at Helmholtz Zentrum Geesthacht (HZG), Germany. The data includes backscatter images collected every 2-min that can be used to identify surface features such as fronts. The data also includes current velocity maps obtained by processing series of these images using 3-D Fast Fourier Transforms (FFTs) and overlays of the current maps over averaged backscatter images. This data was collected in the region of the abandoned Taylor Energy platform in the northern Gulf of Mexico. The data includes radar backscatter images as well as derived surface velocity maps. This dataset supports the publication: Androulidakis, Y., Kourafalou, V., Özgökmen, T., Garcia‐Pineda, O., Lund, B., Le Hénaff, M., Hu, C., Haus, B.K., Novelli, G., Guigand, C. and Kang, H., 2018. Influence of River‐Induced Fronts on Hydrocarbon Transport: A Multiplatform Observational Study. Journal of Geophysical Research: Oceans. doi:10.1029/2017jc013514

Suggested Citation:

Brian Haus , Bjoern Lund, Tamay M. Ozgokmen, Jochen Horstmann. 2018. Radar measurements collected during the Submesoscale Processes and Lagrangian Analysis on the Shelf (SPLASH) experiment aboard R/V Walton Smith cruise WS17107 near the Taylor Energy oil leak site in the Gulf of Mexico from 2017-04-19 to 2017-04-21. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7RR1WV5

Publications:

Androulidakis, Y., Kourafalou, V., Özgökmen, T., Garcia-Pineda, O., Lund, B., Le Hénaff, M., … Horstmann, J. (2018). Influence of River-Induced Fronts on Hydrocarbon Transport: A Multiplatform Observational Study. Journal of Geophysical Research: Oceans. doi:10.1029/2017jc013514

Purpose:

To observe the transport and dispersion of oil released from the Taylor platform as it interacted with wind, waves and currents. To achieve this overall purpose the processing of the data had three sub-purposes: 1) to identify oceanic frontal features from backscatter images within a 3-km radius of the RV Walton Smith 2) to measure ocean wave spectra from wave patterns observed in the backscatter images 3) to map oceanic near surface currents using temporal stacks of consecutive images.

Data Parameters and Units:

Backscatter strength (Db, grey scale 16 bit images); ux (zonal component (west-east direction) of near-surface current, m/s); uy (meridional component (south-north direction) of near-surface current, m/s); xCoords (x coordinates (west-east direction), m); yCoords (y coordinates (south-north direction), m); time (year day; 0.5 corresponds to 01/01/2017, 12:00 UTC, days); imageOriginPosition(geographic coordinates of map origin, i.e., (0 m, 0 m) on (x, y) grid, degrees east, degrees north); startTime (start time in year days; 0.5 corresponds to 01/01/2017, 12:00 UTC, days); endTime (end time in year days; 0.5 corresponds to 01/01/2017, 12:00 UTC, days), nSpec (number of spectra). Dataset contains netCDF files for near-surface currents, kmz files for backscatter and a quick view map (jpg files) of the backscatter and derived near-surface currents.

Methods:

The backscatter images and near-surface current maps archived here were collected with a HZG MR that was installed on RV F. G. Walton Smith during the SPLASH experiment near the Mississippi River mouth in April 2017. The study area is affected by the mesoscale eddy field associated with the Gulf of Mexico (GoM) loop current, the Mississippi River discharge, and wind stress. It is characterized by strong horizontal density gradients that are responsible for especially active submesoscale currents. This sub-set of the SPLASH data was collected in the vicinity of the disabled Taylor oil platform leak.

Instruments:

A DopplerMR developed at the Helmholtz Zentrum Geesthacht (HZG), Germany, was mounted at ~12.5 m above sea level on a mast on top of the wheel-house of RV F. G. Walton Smith. The HZG MR is based on a commercial marine X-band (9.4 GHz) radar with a 7.5-foot HH-polarized antenna, 12 kW peak power output, and an antenna rotation period of 2 s. It was modified to operate as a coherent-on-receive system, measuring both phase and intensity of the radar backscatter (Braun et al. 2008).

Error Analysis:

The MR–drifter current comparison presented reported in Lund et al. 2018 (JTECH) is of an unprecedented size and scope. A total of 4130 data pairs (from 240 MR analysis periods corresponding to ~5.8 days of measurements) are available, covering winds from 2-12 m/s. The comparison statistics indicate a measurement accuracy that is significantly better than any previously reported results, with RMS errors of 3.5 cm/s for u and 4.0 cm/s for v.

Provenance and Historical References:

Braun, N., Ziemer, F., Bezuglov, A., Cysewski, M. and Schymura, G., 2008. Sea-surface current features observed by Doppler radar. IEEE Transactions on Geoscience and Remote Sensing, 46(4), pp.1125-1133. Lund, B., Haus, B.K., Horstmann, J., Graber, H.C., Carrasco, R., Laxague, N.J., Novelli, G., Guigand, C.M. and Özgökmen, T.M., 2018. Near-surface current mapping by shipboard marine X-band radar: A validation. Journal of Atmospheric and Oceanic Technology, 35(5), pp.1077-1090. Lund, B., Collins, C.O., Tamura, H. and Graber, H.C., 2016. Multi-directional wave spectra from marine X-band radar. Ocean Dynamics, 66(8), pp.973-988. Lund, B., Graber, H.C., Hessner, K. and Williams, N.J., 2015. On shipboard marine X-band radar near-surface current ‘‘calibration’’. Journal of Atmospheric and Oceanic Technology, 32(10), pp.1928-1944. Lund, B., Graber, H.C., Tamura, H., Collins III, C.O. and Varlamov, S.M., 2015. A new technique for the retrieval of near‐surface vertical current shear from marine X‐band radar images. Journal of Geophysical Research: Oceans, 120(12), pp.8466-8486.

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