8
1 Introduction to the Concepts and Use of ERA Acute
1.4 Inputs Needed for ERA Acute
1.4.1 Oil Spill Trajectory Modelling
ERA Acute does not include an oil spill trajectory model. Oil drift simulation models
used should provide results from a multitude of single simulations exported to a
standardized grid format. Each simulation has a start date and a duration, which is
used to identify the relevant month. Each cell in each simulation has output values
of the necessary oil inputs.
Although the ERA Acute project has used SINTEFs oil spill trajectory model Oil
Spill Contingency And Response (OSCAR) as an example for development purposes,
oil drift simulations are carried out separately using any preferred oil drift model that
can provide the necessary parameters in the right format for input to ERA Acute.
The format (the parameters and their units) is specified a separate report (Brönner
et al. 2017).
A Defined Situation of Hazard and Accident (DSHA) may consist of one or several
scenarios (see Sect. 3.1) where each scenario represents a rate-duration combination
and a spill location depth and is modelled in numerous simulations. The scenarios
have different probabilities, defined by a probability distribution. Single simulation
results must contain the oil exposure-related input parameters for each compartment
in each cell. Initial impacts are calculated in individual cells of single simulations for
every VEC. The impact mechanisms are different in each compartment. Results from
the cells and simulations are aggregated to scenario statistics and DSHA assessments
using the probability distributions of the individual rates, durations and spill depth.
In this way, results are averaged and/or summarized in a series of steps that allow the
investigation of results at several levels. Impacts can be viewed in individual cells
and for single simulations or can be summarized for scenarios or whole DSHAs. A
case can consist of one or more DSHAs.
In order to include the large variation in drift and fate of the oil following an
accidental oil spill, the oil spill modelling is carried out using a stochastic approach
with numerous simulation runs using different historical start dates, representing a
variety of wind and current situations throughout the simulated spill and modelling
duration from a hindcast archive of historical wind and current. The output is a
significantly large number of spill simulations, each representing a historical situation
of how the oil spill would have behaved and impacted different areas on the sea
surface, water column, seafloor or shoreline had it started on a specific historic date.
In this way seasonal and annual variations are included in the statistical results. For
each oil spill simulation, various endpoint parameters are recorded for each grid cell
that will be used to quantify the impact (mortality or habitat loss) for various VECs.
This includes parameters like:
• oil mass and oil film thickness on the sea surface
• surface oil coverage in grid cell above a threshold film thickness
• accumulated oil mass in shoreline or seafloor grid cells
1 Introduction to the Concepts and Use of ERA Acute
1.4 Inputs Needed for ERA Acute
1.4.1 Oil Spill Trajectory Modelling
ERA Acute does not include an oil spill trajectory model. Oil drift simulation models
used should provide results from a multitude of single simulations exported to a
standardized grid format. Each simulation has a start date and a duration, which is
used to identify the relevant month. Each cell in each simulation has output values
of the necessary oil inputs.
Although the ERA Acute project has used SINTEFs oil spill trajectory model Oil
Spill Contingency And Response (OSCAR) as an example for development purposes,
oil drift simulations are carried out separately using any preferred oil drift model that
can provide the necessary parameters in the right format for input to ERA Acute.
The format (the parameters and their units) is specified a separate report (Brönner
et al. 2017).
A Defined Situation of Hazard and Accident (DSHA) may consist of one or several
scenarios (see Sect. 3.1) where each scenario represents a rate-duration combination
and a spill location depth and is modelled in numerous simulations. The scenarios
have different probabilities, defined by a probability distribution. Single simulation
results must contain the oil exposure-related input parameters for each compartment
in each cell. Initial impacts are calculated in individual cells of single simulations for
every VEC. The impact mechanisms are different in each compartment. Results from
the cells and simulations are aggregated to scenario statistics and DSHA assessments
using the probability distributions of the individual rates, durations and spill depth.
In this way, results are averaged and/or summarized in a series of steps that allow the
investigation of results at several levels. Impacts can be viewed in individual cells
and for single simulations or can be summarized for scenarios or whole DSHAs. A
case can consist of one or more DSHAs.
In order to include the large variation in drift and fate of the oil following an
accidental oil spill, the oil spill modelling is carried out using a stochastic approach
with numerous simulation runs using different historical start dates, representing a
variety of wind and current situations throughout the simulated spill and modelling
duration from a hindcast archive of historical wind and current. The output is a
significantly large number of spill simulations, each representing a historical situation
of how the oil spill would have behaved and impacted different areas on the sea
surface, water column, seafloor or shoreline had it started on a specific historic date.
In this way seasonal and annual variations are included in the statistical results. For
each oil spill simulation, various endpoint parameters are recorded for each grid cell
that will be used to quantify the impact (mortality or habitat loss) for various VECs.
This includes parameters like:
• oil mass and oil film thickness on the sea surface
• surface oil coverage in grid cell above a threshold film thickness
• accumulated oil mass in shoreline or seafloor grid cells