Physical Transport Group

Trajectory Time and Length Scale Discussion

There are three temporal phases to oil spill issues: planning for a potential incident, response to an incident, and recovery and restoration after an incident. Below are tables that outline the types of physical information that are useful for each of these three phases. Within each table the timescales are further divided along the columns, and issues are identified in the lower rows.

Planning involves looking at a variety of time-scales in order to ensure that plans in place take into account the range of variability in the physical system.

Planning (Timescale)

Issues / Short
(Minutes to Days) / Medium
(Days to Months) / Long
(Multi year) / Interdecadal / Climate Change Trend
Wind rose
Tidal charts
River flow/gage data
General conservation principles / Forecasts
Seasonal transition occurance
Meterological storm time scale and tracks / Long record Climatology
Monsoon
Eddy dynamics and statistics
Gulf stream meanders
Seasonal reversals / Ex: El Nino / Ex: Summer extent of arctic sea ice
Likely locations
(spill start sites) / X / X / X / X
Response Resources Needs / X
Equipment Storage / X / X
Disposal / X / x
Transit times / X / X
Shipping routes / X / X / X / X
Model type / Persistence / Deterministic advection and diffusion
Ensemble forecast / Analysis of multiple trajectories
Random process / Sensitivity analysis / Climate model

Response to oil spill events have both a time-scale for when the prediction is needed as well as inherent timescales in the processes modeled. Below are matrices for both types of timescales.

Getting information to Decision Makers in time to make selections among response options is key for success during a response. Below is a matrix indicating these timescales and the types of information associated with them.

Response / Tactical Modeling – When the model product is needed by Decision Makers.

Early moments / 1st hour / Hours / Planning cycle (24-36 hr) / Days - Weeks
Beach pre-cleaning / X / X / X / X
Response options
Dispersants / X
Burning / X
Boom / X
Mystery spill source ID / X / X
Trajectory / X / X / X / X

During the emergency portion of the response, a variety of model types may be used from a description of how the incident will unfold from the forecasters knowledge and experience, to the use of both diagnostic and prognostic physical models.

Response / Tactical Modeling – Model Types

Short
(Minutes to Days) / Medium
(Days to Months) / Long
(Multi year) / Interdecadal / Climate Change Trend
Wave dynamics
Langmuir circ.
Rip current dynamics
Tides
Mixed layer dynamics / Tides
Shelf waves
Alterations in mixed layer
Thermocline development
Coastal current dynamics
Freshwater outflow / Seasonal variations (no model is needed) / Climatology
Beach precleaning / X / X
Preplacement of boom / X / X
Response options / X
Dispersants / X / X
Burning / X
Boom / X / X
Skimming / X / X
Mystery spill source ID / X / X
Trajectory / X / X / X
Well Blowout / X / X
Model Type (state of the art) / Persistence / Persistence with temporal forecast and simple error estimates. / Large numbers of trajectories (eg hundreds) based on long-term (eg decadal) information (wind history, tides) for evaluation of statistical variation.
No models that look at multi-year predictions as for population effects.
Future model type / Multiple scale model (intention of parameterization) / Mulitple scale model with verified prediction, data assimilation and error estimates.


During the later parts of the emergency phase, and restoration planning begins and when estimating Natural Resource Damage Assessmemt, longer term models are again needed.

Restoration, Recovery and Natural Resource Damage Assessment

Hindcast / Medium Timescale
(Weeks to Months) / Prediction /
Long Timescale
(Multi year) / Interdecadal
Tides
Shelf waves
Alterations in mixed layer
Thermocline development
Coastal current dynamics
Freshwater outflow / Tides
Changes in runoff and river discharge (annual and Interannual)
Coastal current dynamics
Long time period predictions for boundary conditions / Climatology
Natural Resource Damage Assessment / X
Restoration options / X
Population Recovery / X
Ecological Recovery / X
Model Type (state of the art) / X,Y model with limited Z dependence that uses historic time period data (eg wind, current meter) data to force model; well verified prediction. / None at this time
Future model type / Mulitple-scale using historic time period data (e.g. winds, current meter) to force model; well verified prediction; error estimates.