Abstract:

The dataset contains the numerical results of probabilistic forecasts for possible oil spills in the Northwest African continental Shelf, around Senegal. The origin of possible oil spills scenarios are deep wells proposed to operate in and around Cayar Canyon (Senegal). Oil dispersal and concentrations were simulated using the latest updated version of the oil application of the Connectivity Modeling System (CMS) or oil- CMS. In this version, the specified hydrocarbon pseudo-components are in the same droplet. The post-processing analysis yielded 4-D spatiotemporal data of the oil concentrations and oil mass on a regular horizontal and vertical grid, as well as time evolution of the horizontally cumulative oil mass for a period of nearly 6 months. The oil spill scenario modeled a blowout location at 15.552N, 17.566W, the oil droplets are released at 1222m depth, or 300m above the hypothetical oil well, an oil spill scenario similar to that of Deepwater Horizon in 2010. 3000 particles were released every 2 hours, for 87 days, equivalent to total of 3132000 oil particles released during the simulation. Initial particle sizes were determined at random by the CMS in the range of 1-500 micron. Each particle contained three (3) pseudo-components accounting for the differential oil density as follows: 10% of light oil with the density of 800kg/m^3, 75% of the oil with 840 kg/m^3, and 15% of a heavy oil with 950 kg/m^3 density. The half-life decay rates of oil fractions were 30 days, 40 days, and 180 days, respectively. The surface evaporation half-life was set to 250 hours; horizontal diffusion was set to 10 m^2/s in the present case. Ocean hydrodynamic forcing for the CMS model used two nests to have high-resolution data in the vicinity of a blowout location, and larger spatial coverage with lower-resolution data. High-resolution Regional Ocean Modeling System (ROMS) v3.7 hindcast model output was used to provide the most detailed information in the region bounded by 12.43N to 22.22N, and -27.47W to -15.93W. Outer nest used the HYbrid Coordinate Ocean Model (HYCOM) global model grid with 0.08-degree horizontal resolution and 40 vertical levels from the surface to 5500m. Large-scale currents from global 0.08-degree HYCOM model, (GLBu0.08/expt_19.1) restricted from 37°W to 12°W and from 9°N to 22.3°N. The ocean models provided daily average 3-D momentum, temperature and salinity forcing fields to the CMS model. The surface wind drift parameterization used surface winds and wind stresses from the Climate Forecast System Reanalysis CFSR/CFSv2. The transport and evolution of the oil particles were tracked by the oil-CMS model during the 167 days of the simulation, recording each particle’s horizontal position, depth, diameter, and density into the model output every 2 hours. Model data had to be post-processed to obtain oil concentrations estimates. The post-processing algorithm took into account the total amount of oil spilled during the 87-day incident as estimated from the reports (730000 tons). Results from the recent laboratory deep-pressure oil experiment and from the observational studies in post-Deepwater Horizon disaster were used to adopt presumed initial droplet size distribution (DSD) for the cases of untreated oil and for the oil treated with a subsea injection of chemical dispersants. The post-processing algorithm then utilized the change-of-variable technique for the probability density functions to obtain an oil mass distribution from a known DSD. A scaling factor was further determined to obtain a representative particle mass and then the volumetric concentration in water. Two postprocessing options were assumed with different initial DSD, corresponding to the untreated oil, and oil treated with subsea dispersant injection (SSDI) that shifts the modal peak in DSD to a smaller droplet. This dataset supports the publications: Paris, C. B., Vaz, A. C., Berenshtein, I., Perlin, N., Faillettaz, R., Aman, Z. M., & Murawski, S. A. (2019). Simulating Deep Oil Spills Beyond the Gulf of Mexico. Scenarios and Responses to Future Deep Oil Spills, 315–336. doi:10.1007/978-3-030-12963-7_19; and Paris, C. B., Murawski, S. A., Olascoaga, M. J., Vaz, A. C., Berenshtein, I., Miron, P., & Beron-Vera, F. J. (2019). Connectivity of the Gulf of Mexico Continental Shelf Fish Populations and Implications of Simulated Oil Spills. Scenarios and Responses to Future Deep Oil Spills, 369–389. doi:10.1007/978-3-030-12963-7_22.

Suggested Citation:

Claire B. Paris, Natalie Perlin, Ana C. Vaz. 2019. Three-dimensional daily hindcast of oil concentrations and oil mass estimates from the far-field modeling of a deep water spill scenario in the Northwest African continental Shelf, using the Connectivity Modeling System on a probabilistic approach. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/n7-5nnq-n089

Publications:

Paris, C. B., Murawski, S. A., Olascoaga, M. J., Vaz, A. C., Berenshtein, I., Miron, P., & Beron-Vera, F. J. (2019). Connectivity of the Gulf of Mexico Continental Shelf Fish Populations and Implications of Simulated Oil Spills. Scenarios and Responses to Future Deep Oil Spills, 369–389. doi:10.1007/978-3-030-12963-7_22

Paris, C. B., Vaz, A. C., Berenshtein, I., Perlin, N., Faillettaz, R., Aman, Z. M., & Murawski, S. A. (2019). Simulating Deep Oil Spills Beyond the Gulf of Mexico. Scenarios and Responses to Future Deep Oil Spills, 315–336. doi:10.1007/978-3-030-12963-7_19

Purpose:

We simulate a Deepwater Horizon (DWH)-like spill in a deepwater prospect block offshore Senegal, West Africa, to evaluate its extent and impact against the DHW oil spill hindcast as a benchmark.

Data Parameters and Units:

Parameters: Oil_conc [Oil concentration; parts per billion (ppb)]; Time [time, seconds from release]; lat [Latitude, degrees north], lon [Longitude, degrees east]; oil_mass [kg of crude oil], depth [meters]. Time scale for the 3D oil concentrations: daily averages. 3D data is given for the "untreated oil" case only. Horizontal grid: 0.02-degree spacing, 9.00- 22.22N, 37W-12W. Vertical grid: 177 levels as following: 0-1m, 1-20m, from 20 to 3500 at 20m, increments, and then below 3500m. Time scale for horizontally-cumulative oil mass: 2-h intervals (7200s); provided for both untreated oil case and for the oil treated with subsea dispersant injection (SSDI). The data for the surface oil concentrations are daily averages in ppb units; the oil mass units are kg of crude oil. Horizontal grid boxes are 0.02 degrees covering the spatial domain 9.00N to 22.22N, and 37.00W to 12.0W; vertical grid extends from the surface to the depth of 3500m at 20m increments, except for the top two layers which are 0-1m and 1-20m. The data for horizontally-cumulative oil mass is in units of kg of crude oil, distributed in the water column on a vertical grid from the surface down to 3500m at 20m increments, and estimated bi-hourly corresponding to the oil-CMS model output interval. Post-processed NetCDF files were created using Matlab software package, v. R2016b. The data files with the 3-D data used compression capability of the NetCDF to keep the file size small; maximum compression or ‘DeflateLevel’ = 9 was used. Numerical simulations and post-processing were performed using a Pegasus supercomputer at the Center of Computational Science, University of Miami, in 2018. The data file in *.txt files lists all the droplets that landed or beached within the simulation domain (and no longer are advanced by the CMS model). Format of the files is the following: first columns is the time in seconds from the initial blowout time, the second column is a depth of a landed particle, the third column is the latitude, the forth column is the longitude, and the last column is a scaled oil mass of the particle in kg.

Individual Files: