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

  • 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.
  • 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.
  • 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
  • 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

The first version of this model was developed during the CleanAtlantic project (EAPA_165/2016)
funded by INTERREG Atlantic Area programme