Numerical simulation of the movement of the 1991 oil spills in the Arabian Gulf

The output from the modified version of a hydrodynamical numerical model developed earlier by El-Sabh and Murty (1988) has been used to hindcast the movement and dispersion of oil slicks in the Arabian Gulf during part of the period of January to March 1991. While other studies on numerical simulations of the event pertain mainly to the Al-Ahmadi spill, the present study simultaneously examines the movement of oil from not only this source but also from Mina Al-bakr and clearly delineates the impact of oil from each of these sources. The numerical model is used to compute the current due to tides, winds and bathymetric influences. This model has only one open boundary at the strait of Hormuz where the incoming tide is prescribed. The model time step is 100 seconds, sufficient to resolve the hydrodynamical effects. However, the slick movement simulations are carried out with current fields determined at hourly intervals. The surface wind field has been computed from synoptic weather charts using the geostropic relationship, supplemented by some climatological data. The oil slick is advanced by the net current as obtained above and the lateral spreading of the oil is simulated through a random walk process with an appropriate eddy diffusion coefficient. The influence of the magnitude of the eddy diffusion coefficient on the spread of the oil is examined in detail. Refloatation of beached oil parcels is also considered in the model simulations. The model simulations are compared with slick location as obtained from remotely sensed observations. The importance of real-time winds in spill movement prediction is demonstrated through a comparison with model simulations obtained with monthly mean climatological winds. 19 refs., 15 figs