# Trajectory Tool Simulator

In each test site, an ocean circulation model has been developed.

These numerical models solve the equations of motion (Navier-Stokes) in a discretised spatial and temporal domain. The numerical resolution is the only way to get a solution (velocity and density 3-dimensional field and temporal evolution) to this unresolved analytical problem (non linear and turbulent), but includes strong approximations that should be taken into account when looking at the numerical solution and the forecast.

Coupled with the ocean general circulation models, different Lagrangian modules (GNOME, ARIANE, Medslick, Runge-Kutta advection scheme,…) simulate the motion of particles advected (ie transported) by the currents, as oil-spill, wreckage or drifting body. This particle motion could be passive (without any exchange with the ambient mean) or active (chemical transformation).

This **Interactive** DEMO simulator is based on Runge-Kutta advection scheme, using the numerical simulations in the Gulf of Lions, based on the NEMO numerical model.

The trajectory of a passive element transported by the ocean surface currents only (no wind effect) is simulated, according to the starting date and the duration of the trajectory, and multiple trajectories can be superimposed on the same picture.

# Dispersion Maps

GNOME (General NOAA Operational Modeling Environment) is the NOAA modeling tool used to predict the possible route, or trajectory, a pollutant might follow in or on a body of water, such as in an oil spill. It takes into account the current, the wind and the diffusion.

Dispersion maps can be obtained using a background velocity field (from ocean general circulation models or from HF-radar maps), wind data sets and empirical diffusion coefficients.

Some examples of dispersion maps are shown according to the region, the date and the initial deploiment (homogeneous or targeted).

The LAVA (Lagrangian Variational Analysis) algorithm allows a joint use of measurements from HF radar and drifters, in order to provide optimized estimates of currents and their associated transport.

The algorithm is now specifically customized for TOSCA applications, combining the use of drifters data with model forecast, and the results show the potential on improving transport prediction in case of accidents at sea

The improved algorithm is flexible and can use as input velocity fields from either models or HF radar. These velocity fields are corrected and optimized using drifter data with a technique developed in the framework of Lagrangian data assimilation. Conceptually, the observed in-situ drifter trajectories are compared with synthetic trajectories computed from the input velocity fields, and the distance between the two sets is minimized correcting the velocity field appropriately. In other words, the velocity field is optimized for transport as measured by the drifters. The improved algorithm has been streamlined and customized specifically for TOSCA needs.

This tool (under development) will allow you to run LAVA correction algorithm.
In the scope of the TOSCA Project, it is only a DEMO of what will be possible to do using LAVA correction algorithm.
It has been designed to be operationnal during a specific period (2012 August Campaign) on a specific site (TOULON).

- This tool will allow you to compare the actual velocity field and the lava generated one.
- You will have the possibility to choose some argument before invoking lava.
- The number of drifters to use (any combination of integers from 1 to 7)
- The duration of a sequence for the analysis (jtlag),
- The spatial length scale of the analysis (lenfil is 3.0 km,7.0 km and 14.0 km)

- Draw trajectories of synthetic drifters placed inside both velocity fields.