Abstract:

This dataset reports near-surface currents and sea surface roughness derived from X-band radar aboard R/V Walton Smith cruise WS16015 in the Gulf of Mexico from 2016-01-20 to 2016-02-12. This data was collected during the CARTHE II sponsored LAgrangian Submesoscale ExpeRiment (LASER) 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 dataset supports the publication: 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. doi:10.1175/jtech-d-17-0154.1

Suggested Citation:

Bjoern Lund, Brian Haus. 2018. Radar measurements collected during the LAgrangian Submesoscale ExpeRiment (LASER) experiment aboard R/V Walton Smith cruise WS16015 in the Gulf of Mexico from 2016-01-20 to 2016-02-12. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/N7N01550

Publications:

Lund, B., Haus, B. K., Horstmann, J., Graber, H. C., Carrasco, R., Laxague, N. J. M., … Özgökmen, T. M. (2018). Near-Surface Current Mapping by Shipboard Marine X-Band Radar: A Validation. Journal of Atmospheric and Oceanic Technology, 35(5), 1077–1090. doi:10.1175/jtech-d-17-0154.1

Carlson, D. F., Özgökmen, T., Novelli, G., Guigand, C., Chang, H., Fox-Kemper, B., … Horstmann, J. (2018). Surface Ocean Dispersion Observations From the Ship-Tethered Aerostat Remote Sensing System. Frontiers in Marine Science, 5. doi:10.3389/fmars.2018.00479

Shao, M., Ortiz‐Suslow, D. G., Haus, B. K., Lund, B., Williams, N. J., Özgökmen, T. M., … Klymak, J. M. (2019). The Variability of Winds and Fluxes Observed Near Submesoscale Fronts. Journal of Geophysical Research: Oceans, 124(11), 7756–7780. doi:10.1029/2019jc015236

Pearson, J., Fox‐Kemper, B., Pearson, B., Chang, H., Haus, B. K., Horstmann, J., … Poje, A. (2020). Biases in Structure Functions from Observations of Submesoscale Flows. Journal of Geophysical Research: Oceans, 125(6). doi:10.1029/2019jc015769

Berta, M., Griffa, A., Haza, A. C., Horstmann, J., Huntley, H. S., Ibrahim, R., … Poje, A. C. (2020). Submesoscale Kinematic Properties in Summer and Winter Surface Flows in the Northern Gulf of Mexico. Journal of Geophysical Research: Oceans, 125(10). doi:10.1029/2020jc016085

Rascle, N., Chapron, B., Molemaker, J., Nouguier, F., Ocampo‐Torres, F. J., Osuna Cañedo, J. P., … Horstmann, J. (2020). Monitoring Intense Oceanic Fronts Using Sea Surface Roughness: Satellite, Airplane, and In Situ Comparison. Journal of Geophysical Research: Oceans, 125(8). doi:10.1029/2019jc015704

Purpose:

This data had three 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 Lagrangian Submesoscale Experiment (LASER) near the Mississippi River mouth in early 2016. 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.

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., 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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