MEDSLIK-II, a Lagrangian marine surface oil spill model for short-term forecasting – Part 2: Numerical simulations and validations

Abstract. In this paper we use MEDSLIK-II, a Lagrangian marine surface oil spill model described in Part 1 (De Dominicis et al., 2013), to simulate oil slick transport and transformation processes for realistic oceanic cases, where satellite or drifting buoys data are available for verification. The model is coupled with operational oceanographic currents, atmospheric analyses winds and remote sensing data for initialization. The sensitivity of the oil spill simulations to several model parameterizations is analyzed and the results are validated using surface drifters, SAR (synthetic aperture radar) and optical satellite images in different regions of the Mediterranean Sea. It is found that the forecast skill of Lagrangian trajectories largely depends on the accuracy of the Eulerian ocean currents: the operational models give useful estimates of currents, but high-frequency (hourly) and high-spatial resolution is required, and the Stokes drift velocity has to be added, especially in coastal areas. From a numerical point of view, it is found that a realistic oil concentration reconstruction is obtained using an oil tracer grid resolution of about 100 m, with at least 100 000 Lagrangian particles. Moreover, sensitivity experiments to uncertain model parameters show that the knowledge of oil type and slick thickness are, among all the others, key model parameters affecting the simulation results. Considering acceptable for the simulated trajectories a maximum spatial error of the order of three times the horizontal resolution of the Eulerian ocean currents, the predictability skill for particle trajectories is from 1 to 2.5 days depending on the specific current regime. This suggests that re-initialization of the simulations is required every day

Oil spill forecasting in the Mediterranean Sea

In this work sensitivity experiments to the coupled MFS (currents) and MEDSLIK (oil spill) input parameters will be shown and results will be compared with observations. In these experiments the drift angle, the drift factor, the currents depth, the type of oil, horizontal diffusivity and the horizontal and temporal current resolution were changed

The ability of a barotropic model to simulate sea level extremes of meteorological origin in the Mediterranean Sea, including those caused by explosive cyclones

Storm surges are responsible for great damage to coastal property and loss of life every year. Coastal management and adaptation practices are essential to reduce such damage. Numerical models provide a useful tool for informing these practices as they simulate sea level with high spatial resolution. Here we investigate the ability of a barotropic version of the HAMSOM model to simulate sea level extremes of meteorological origin in the Mediterranean Sea, including those caused by explosive cyclones. For this purpose, the output of the model is compared to hourly sea level observations from six tide gauge records (Valencia, Barcelona, Marseille, Civitavecchia, Trieste, and Antalya). It is found that the model underestimates the positive extremes significantly at all stations, in some cases by up to 65%. At Trieste, the model can also sometimes overestimate the extremes significantly. The differences between the model and the residuals are not constant for extremes of a given height, which limits the applicability of the numerical model for storm surge forecasting because calibration is difficult. The 50 and 10 year return levels are reasonably well captured by the model at all stations except Barcelona and Marseille, where they are underestimated by over 30%. The number of exceedances of the 99.9th and 99.95% percentiles over a period of 25 years is severely underestimated by the model at all stations. The skill of the model for predicting the timing and value of the storm surges seems to be higher for the events associated with explosive cyclones at all stations

High-resolution nested model for the Lebanese coastal area, Eastern Mediterranean: implementation and climatological runs

International audienceAs a part of the project Mediterranean Network to Assess and Upgrade Monitoring and Forecasting Activity in the Region (MAMA) we implemented a high resolution nested hydrodynamic model (1/40° horizontal grid, 16 sigma levels) for the coastal, shelf and open sea areas off the Lebanese coast, East Levantine Basin of the Eastern Mediterranean Sea. The Lebanese Shelf Model (LSM) is a version of the Princeton Ocean Model (POM). It is nested in a coarse resolution model the Aegean Levantine Eddy Resolving Model (1/20° horizontal grid, 25 sigma levels), ALERMO, that covers the Eastern Mediterranean. The nesting is one way so that velocity, temperature, and salinity along the open boundaries are interpolated from the relevant coarse model variables. Numerical simulations have been carried out under climatological surface and lateral forcing. Due to the relatively small domain, the results closely follow the simulation of the intermediate model with more details especially over the narrow shelf region. Simulations reproduce main circulation features and coastal circulation characteristics over the eastern Levantine shelf. This paper describes the modeling system setup, compares the simulations with the corresponding results of the coarse model ALERMO, and with the observed climatological circulation characteristics in the Levantine Basin off the Lebanese coast

Predictions for oil slicks detected from satellite images using MyOcean forecasting data

The pan-European capacity for the Ocean Monitoring and Forecasting (MyOcean) Marine Core Service, implementing the Global Monitoring for Environment and Security (GMES) objectives, targets the provision of ocean state observations from various platforms and analysis and forecasting products to assist, among other downscaling activities, the needs of the operational response to marine safety, particularly concerning oil spills. The MEDSLIK oil spill and trajectory prediction system makes use of the MyOcean regional and Cyprus Coastal Ocean Forecasting and Observing System (CYCOFOS) downscaled forecasting products for operational application in the Mediterranean and pre-operational use in the Black Sea. Advanced Synthetic Aperture Radar (ASAR) satellite remote sensing images from the European Space Agency (ESA) and European Maritime Safety Agency CleanSeaNet (EMSA-CSN) provide the means for routine monitoring of the southern European seas for the detection of illegal oil discharges. MEDSLIK offers various ways, to be described in this paper, of coupling the MyOcean forecasting data with ASAR images to provide both forecasts and hindcasts for such remotely observed oil slicks. The main concern will be the drift of the oil slick and also, in the case of the forecast mode, its diffusive spreading, although some attempt is also made to estimate the changes in the state of the oil. The successful link of the satellite-detected oil slicks with their operational predictions using the MyOcean products contributes to the operational response chain and the strengthening of maritime safety for accidental or illegal spills, in implementation of the Mediterranean Decision Support System for Marine Safety (MEDESS-4MS) regarding oil spills

Operational ocean forecasting in the Eastern Mediterranean: implementation and evaluation

The Cyprus Coastal Ocean Forecasting and Observing System (CYCOFOS) has been producing operational flow forecasts of the northeastern Levantine Basin since 2002 and has been substantially improved in 2005. CYCOFOS uses the POM flow model, and recently, within the frame of the MFSTEP project, the flow model was upgraded to use the hourly SKIRON atmospheric forcing, and its resolution was increased from 2.5 km to 1.8 km. The CYCOFOS model is now nested in the ALERMO regional model from the University of Athens, which is nested within the MFS basin model. The Variational Initialization and FOrcing Platform (VIFOP) has been implemented to reduce the numerical transient processes following initialization. Moreover, a five-day forecast is repeated every day, providing more detailed and more accurate information. Forecast results are posted on the web page http://www.oceanography.ucy.ac.cy/cycofos. The new, daily, high-resolution forecasts agree well with the ALERMO regional model. The agreement is better and results more reasonable when VIFOP is used. Active and slave experiments suggest that a four-week active period produces realistic results with more small-scale features. For runs in September 2004, biases with remote sensing sea surface temperature are less than 0.6°C with similar expressions of the flow field present in both. Remotely-observed coastal upwelling south of Cyprus and advection of cool water from the Rhodes Gyre to the southern shores of Cyprus are also modeled. In situ observed hydrographic data from south of Cyprus are similar to the corresponding forecast fields. Both indicate the relatively fresh subsurface Atlantic Water and a near-surface anticyclone south of Cyprus for August/September of 2004 and September 2005. Plans for further model improvement include assimilation of observed XBT temperature profiles, CTD profiles from drifters and gliders, and CT data from the CYCOFOS ocean observatory

MEDSLIK-II, a Lagrangian marine surface oil spill model for short-term forecasting – Part 1: Theory

The processes of transport, diffusion and transformation of surface oil in seawater can be simulated using a Lagrangian model formalism coupled with Eulerian circulation models. This paper describes the formalism and the conceptual assumptions of a Lagrangian marine surface oil slick numerical model and rewrites the constitutive equations in a modern mathematical framework. The Lagrangian numerical representation of the oil slick requires three different state variables: the slick, the particle and the structural state variables. Transformation processes (evaporation, spreading, dispersion and coastal adhesion) act on the slick state variables, while particle variables are used to model the transport and diffusion processes. The slick and particle variables are recombined together to compute the oil concentration in water, a structural state variable. The mathematical and numerical formulation of oil transport, diffusion and transformation processes described in this paper, together with the many simplifying hypothesis and parameterizations, form the basis of a new, open source Lagrangian surface oil spill model, the so-called MEDSLIK-II, based on its precursor MEDSLIK (Lardner et al., 1998, 2006; Zodiatis et al., 2008a). Part 2 of this paper describes the applications of the model to oil spill simulations that allow the validation of the model results and the study of the sensitivity of the simulated oil slick to different model numerical parameterizations

Hindcast of Oil Spill Pollution during the Lebanon Crisis, July-August 2006

The Mediterranean Operational Oceanography Network (MOON ) provides near-real-time information on oil spill detection and predictions that have been used during the Lebanese oil pollution crisis in summer 2006. A MOON decision support system for oil spill monitoring and prediction comprising ocean colour satellite and SAR images, ocean current forecast (MFS-Mediterranean Forecasting System and CYCOFOS-CYprus Coastal Ocean Forecasting & Observing System) and the MEDSLIK oil spill model has been developed. The oil spill predictions obtained with MEDSLIK coupled to the CYCOFOS high-resolution ocean fields are compared with the oil spill predictions obtained using the lower resolution MFS hydrodynamics and both are validated against satellite observations. The predicted beached oil quatity along the Lebanese and Syrian coasts are compared with the in-situ observations. It is found that predictions with both CYCOFOS and MFS ar capable to simulate the northward movement of the oil, with the higher resolution CYCOFOS predictions in better agreement with satellite observations. Among the free MEDSLIK oil spill parameters tested in the sensitivity experiments there are the wind corrections (wind factor and angle) and the depth of coupling between eulerian fields and wind correction. Among them the drift factor appeared the most relevant in order to improve the quality of results suggesting that operational models such as MFS and CYCOFOS still lack of enought resolution and physical process at the air-sea interface. The oil moved from Lat 33°40'N Lon 35°24.75'E northward toward Syria, which was reached in 10 days at Lat 34° 38.451'N Lon 35° 58.377'E; the oil movement is followed up to August 6 when the oil reached 35.5°N.Not submitted4.6. Oceanografia operativa per la valutazione dei rischi in aree marineJCR Journalope

Hindcast of oil-spill pollution during the Lebanon crisis in the Eastern Mediterranean, July–August 2006

MOON (Mediterranean Operational Oceanography Network http://www.moon-oceanforecasting.eu) pro- vides near-real-time information on oil-spill detection (ocean color and SAR) and predictions [ocean fore- casts (MFS and CYCOFOS) and oil-spill predictions (MEDSLIK)]. We employ this system to study the Lebanese oil-pollution crisis in summer 2006 and thus to assist regional and local decision makers in Europe, regionally and locally. The MEDSLIK oil-spill predictions obtained using CYCOFOS high-resolution ocean fields are compared with those obtained using lower-resolution MFS hydrodynamics, and both are validated against satellite observations. The predicted beached oil distributions along the Lebanese and Syrian coasts are compared with in situ observations. The oil-spill predictions are able to simulate the northward movement of the oil spill, with the CYCO- FOS predictions being in better agreement with satellite observations. Among the free MEDSLIK param- eters tested in the sensitivity experiments, the drift factor appears to be the most relevant to improve the quality of the results.The paper was produced using the INGV MFS forecasting-sys- tem product and the OC-UCY CYCOFOS forecasting-system prod- ucts. The MODIS satellite data products were processed at the GOS-CNR-ISAC Rome laboratory using the SeaDAS software devel- oped by NASA GSFC, Greenbelt, Maryland, the HDFLook software developed by The Laboratoire d’Optique Atmosphérique, Univer- sity of Lille, France, and the MS2GT tool box developed by the Uni- versity of Colorado. Procedures for oil-spill detection were developed in the ENVI environment. Processed ENVISAT-ASAR data were made available by Telespazio and JRC. Part of this work was carried out with the support of the PRIMI project (ASI Contract No. I/094/06/0) financed by the Italian Space Agency (ASI).In press4.6. Oceanografia operativa per la valutazione dei rischi in aree marineJCR Journalreserve