William J. Lehr

Revisions of the ADIOS oil spill model

Abstract For several years, the National Oceanic and Atmospheric Administration Hazardous Materials Response Division (NOAA/HAZMAT) has been using and distributing the computer software package called ADIOS™ (Automated Data Inquiry for Oil Spills) to aid responders in oil spill cleanup. ADIOS forecasts the weathering processes and characteristics of oil slicks. Based on new research results and analysis since the first version was released, a major update revises and improves previous algorithms, plus adds new modules for other weathering processes and for spill cleanup strategies. The weathering processes included in the new version, called ADIOS2, are spreading, evaporation, dispersion, sedimentation, and emulsification. The user cleanup options are dispersants, in-situ burning, and skimming. Different types of release scenarios can be simulated and the user is allowed to enter ranges for selected input variables with the resulting uncertainty displayed in the model output.

The Relation of Langmuir Circulation Processes to the Standard Oil Spill Spreading, Dispersion, and Transport Algorithms

Abstract Most standard oil spill modeling programs neglect the effects of Langmuir circulation (LC). The authors have identified three areas where LC effects may be important in spill behavior. These three areas are spreading, dispersion, and transport. LC will cause the slick to break into windrows when the wind-row formation velocity is comparable to Fay and other spreading forces. Oil dispersion is likely to be enhanced, with droplets carried to greater depth and distributed non-uniformly. Transport velocities for different parts of the slick will vary because of LC, a phenomenon that also occurs because of other factors.

Computation of the residual flow in the Gulf using the Mt Mitchell data and the KFUPM/RI hydrodynamical models☆

The hydrodynamical models of the Gulf developed at KFUPM Research Institute are briefly described. The models are used to compute the flows in the Gulf driven by density gradient using the two sets of data collected on Legs 1 and 6 of the Mt Mitchell cruise. The two flows are compared with one another, with the result of a similar computation using the 1977 Atlantis II data and with computations of the flow driven by the prevailing wind. The combined residual flow due to wind and density gradient is found and compared to empirical estimates of the residual flow derived from ship-drift reports. The accuracy of the models is tested using the computed and observed water velocities at some of the current meters deployed during the cruise.

Trajectory modeling of marine oil spills

Techniques that estimate the past history of a “mystery” spill can assist the forensic investigation. Most spill models are flexible enough to allow for a wide variety of modeling techniques. In general, the models run in either a tactical mode, used for short-term forecasting from a known source or in a statistical mode, using historical environmental conditions to generate a long-term forecast. A modeler uses a forensic approach to investigate the past trajectory of an oil spill. Modelers call this approach a “hind cast” of the spill. In hind casting, the idea with either a forward or backward model run is to “reforecast” the oil movement for a particular spill event and provide investigators an indication when and where the spill occurred. Selecting either a forward or backward option depends upon the question being asked. The first option, running the model forward in time, is used if the location of the oil source is known or needs verification. The second option involves running the model backwards in time from the location where the oil is found.

Modeling the benzene inhalation hazard from spilled oil

Abstract Three different possible models for evaporation of benzene from an oil slick are examined. Each of these hypothesize a different control mechanism to restrict benzene release from the slick. The evaporation models, combined with an air dispersion model, provide airborne benzene estimates. Results are compared with experiments in Mobile Bay.

On mathematical and empirical models for surface oil spill transport in the Gulf

Abstract This paper consists of two parts: in the first part Gulfslik II a mathematical model that simulates surface oil spill transport is tested using the drifting buoys data of the Mt Mitchell cruise. In the second part an empirical formula based on the drift factor approach to estimate surface oil spill transport due to wind is derived.

Wind Uncertainty in Long Range Trajectory Forecasts

ABSTRACT The essential equations of oil spill trajectory modeling have not changed in four decades. The vast majority of existing trajectory models divide the slick up into pieces, called Lagrangian Elements (LEs). The models move the LEs by summing movement vectors related to three somewhat interrelated components; surface water currents, turbulent diffusion, and surface wind stress. Improvement in modeling has consisted, chiefly, of better refining these three components. While such trajectory models generate predictions, the real world is filled with uncertainty. As the spill response community seeks longer-range forecasts, spill models must be able to not only provide a best-guess prediction but also to estimate the likelihood and extent of any errors in the prediction. Wind forecast error often is the major contributor to trajectory error for longer-range forecasts because, more so than currents, wind is subject to rapid change in magnitude and direction. This paper provides a formula to identify a...

Leaking Tank Experiments for Heavy Oils

ABSTRACT During oil spill incidents involving damaged tankers, the amount of product released may be uncertain. Many accidents occur under adverse conditions, so determining the volume lost by sounding the tanks may not be practical. In the first few hours, initial volume estimates often are based on visual observations of the resulting slick, a notoriously unreliable approach. Oils that have special characteristics, such as group V oils and Orimulsion®, that may or may not result in a surface slick, further complicate this problem. The Hazardous Materials Response Division of the National Oceanic and Atmospheric Administration (NOAA/HAZMAT) has developed a leaking tank module for its oil weathering software, ADIOS2. Because the present version of the model is not designed for heavy oils, NOAA/HAZMAT is undertaking a series of model-scale tests using releases of canola oil and Orimulsion®. These tests are an extension of leaking tank experiments done earlier for NOAA and for the U. S. Coast Guard, and are...

SENSITIVITY ANALYSIS IN OIL SPILL MODELS: CASE STUDY USING ADIOS

ABSTRACT The Hazardous Material Response and Assessment Division (HAZMAT) at the National Oceanic and Atmospheric Administration uses the oil weathering software package named Automated Data Inquir...

Extended oil spill spreading with Langmuir circulation

When spilled in the ocean, most crude oils quickly spread into a thin film that ruptures into smaller slicks distributed over a larger area. Observers have also reported the film tearing apart into streaks that eventually merge forming fewer but longer bands of floating oil. Understanding this process is important to model oil spill transport. First, slick area is calculated using a spreading model. Next, Langmuir circulation models are used to approximate the merging of oiled bands. Calculations are performed on Troll blended and Alaska North Slope crude oils and results compared with measurements from the 1990s North Sea field experiments. Langmuir circulation increases the oil area but decreases the surface coverage of oil. This work modifies existing oil spreading formulas by providing a surface area correction due to the effects of Langmuir circulation. The models simplicity is advantageous in situations with limited data, such as emergency oil spill response.