scope:

1.0 INTRODUCTION

This report summarizes the results of the first of a three-phase study project for the American Petroleum Institute (API). The project is to conduct a review and evaluation of the state-of-the-art of oil spill simulation models with an aim of identifying models, or model components, that may be integrated to form a single "state-of-the-art" model for simulating the fate of the spilled oil in the marine environment.

There are essentially the following processes that affect the fact of the spilled oil in the marine environment: advection, spreading, evaporation, emulsification, dispersion, dissolution, biodegradation, photo-oxidation, and sinking/sedimentation. Although these processes have long been identified to affect the fate of the spilled oil, very few of the existing models, as far as we are able to determine, have attempted to include all of these processes in the model. In fact, most of the models developed to date deal only with the drifting and spreading of oil slicks. The other oil weathering processes such as evaporation, dissolution, emulsification, oxidation, and biodradation, etc. have been neglected by a number of reasons including the complexity involved and the lack af sufficient understanding of the mechanisms involved in determining the fate of the spilled oil. Even the spreading of oil slicks on the sea, although it has received a considerable amount of attention in the past decade (Fay, 1969; Blokker, 1964; Murray, 1972; Ichiye, 1972), is still poorly understood. Recently, a few models that simulate the physical advection and spreading processes with reasonably satisfactory results have been developed (e.g. Kollmeyer and Thompson, 1979). There are also other models (e.g. MacKay and Leinonen, 1977) that deal extensively with the physical-chemical processes that determine the movement of oil slicks. A number of models (e.g. Slikforcast, 1980; URI, 1978; Garver and Williams, 1975; USC/API, 1977) have attempted to incorporate both the physical and physical-chemical processes. In addition, a number of studies designed to achieve a better understanding of these processes have been conducted and algorithms for simulating these processes have been proposed. In these models or algorithms, different methods are used to simulate a particular process or set of processes. They need to be evaluated so that the "best elements" that represent the state-of-the-art may be identified and then integrated to form a "state-of-the-art" model.

The above goals are to be achieved in three phases. In the Phase I study, whose results are reported herein, the objective is to gather, update and expand the existing information on oil spill simulation models. In addition, a preliminary review of the acquired models was made to identify those models or model components having the potential of contributing to the state-of-the-art model. A detailed evaluation of the selected models or algorithms will be made in the Phase II study. Afterwards, recommendations for integrating the "best elements" into a state-of-the-art model will be made in Phase III.

In the Phase I study, various information search resources have been utilized, including the computer literature search and consultations with various recognized experts in the oil spill modeling field. More than 1000 references have been screened. Those that contain model descriptions were subjected to a preliminary review of the model (those that have been or can be computer coded to simular the fate of spilled oil). A synopsis for each of the models reviewed is provided in Section 2. Information for some of the models is still being sought. Some models that warrant further detailed evaluation of their capabilities, accuracy, and realism that will be made in the Phase II study are discussed in Section 3. The detailed review of these models will be made in conjunction with the results of recent research for their possible incorporation into the existing models. Based on the preliminary review of the available models, an overview of the state-of-the-art of existing models is presented in Section 3. A bibliography be noted that the materials presented herein represent a preliminary review of the available information. More information may be added as it become available.