MOHID Water Modelling System 

MOHID Lagrangian

3D passive tracers using currents from a MOHID operational application in Vigo coastal area, Galicia, Spain.

MOHID Lagrangian is a comprehensive high-performance Lagrangian tracer model that can perform as library for the MOHID Water Modelling System or as a standalone program.

The library implements the necessary tools to generate a comprehensive Lagrangian tracer model, with sources, sinks, particle types and several options for forcing and Inputs/Outputs.

The MOHID Lagrangian is a specific implementation of the library, designed as a post-processing or online tool, ready to be forced with other results from other circulation models.


The MOHID Lagrangian include among its characteristics:

  • Multi-threaded code, designed for shared memory machines;
  • Robust pre-processing, modelling and post-processing tools;
  • Cross-platform compliant, tested and deployed;
  • Cmake based project, easy to set up for local compilation if required;
  • Ability to model passive, buoyant and degrading tracers;
  • Ability to model millions of tracers in a modest laptop machine;
  • Simple and fully documented simulation set-up files, ready to be abstracted by a User Interface;
  • Documentation on installation, code structure, case preparation, post processing and general usage. Fully self-contained examples to get you started.
Floating passive tracers on a CMEMS Atlantic currents solution.

Main features

Inputs
  • Import currents/waves/wind/salinity/temperature fields from NetCDF-CF files ;
  • Single file or list of files;
  • Import 3D/2D/regular/irregular structured meshes – curvilinear grids not implemented yet.
SolversProvides 1st, 2nd and 4th order integrators.
Sources
  • Define tracer sources in space and time using basic shapes and file defined polygons;
  • Arbitrary lifespan intervals;
  • Arbitrary emission rate: Import data from a file series automatically.
Outputs
  • VTU binary files with xml header;
  • Raw VTK time encoded output, directly compatible with Paraview and other standard post-processors and renderers;
  • Flexible python post processor, using cross-simulation reusable post-processing recipes, ready to be automated;
  • Computation of volumetric averages and cumulative integrations, exporting the results to standard NetCDF files, so you can explore the results using GIS software or publish to a THREDDS Data Server (TDS);
  • Production of high-quality mapped plots and shapefiles using matplotlib and pandas, allowing for arbitrary calendar, integration types, subdomains including polygons and plot type combinations;
  • Postprocessor (NetCDF4):
    • Concentrations on grid or in arbitrary polygons;
    • Residence Time;
    • Particle property average.

Main Processes

Tracers Tracers are just basic tracers (pure Lagrangian)+ ’stuff’
Always 3D entities
Processes
  • Kinematic Lagrangian;
  • Isotropic diffusion;
  • Adaptation length diffusion;
  • Windage;
  • Stokes drift;
  • Buoyancy (time-dependent density fields based on temperature/salinity);
  • Linear degradation;
  • Vertical motion on 2D layers based on local divergence;
  • Resuspension;
  • Beaching and Land interaction:
    • Automatic land masks;
    • Detection of beaching zone;
    • Inclusion of inter-tidal areas;
    • Detection of bed interaction zones.

For more information check the MOHID Lagrangian Installation Guide and the Short User Guide