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Parcels-code/Parcels
Main code for Parcels - a highly customisable Lagrangian simulation framework
Parcels is the core Python package for Lagrangian particle tracking through gridded ocean and circulation model output, used to follow water, plankton, plastic and fish. This branch is v4, and v3 is in maintenance mode on the v3-support branch. It is aimed at oceanographers and climate scientists who already have NetCDF or Zarr model output and want to write their own advection kernels.
The package is split into clear layers. The _core package handles fields, grids, particle sets and output, with separate interpolators for structured and unstructured grids and an SGRID accessor for staggered grids. Verification is taken seriously: unit tests and codecov run in CI, a nightly job tests against upstream dev dependencies, and asv benchmarks live in a separate repo so performance changes can be tracked. Three peer-reviewed papers cover the design and interpolation schemes across versions, which gives the numerical choices a citable paper trail.
The README is almost all badges and links, so getting started means leaving the repo for an external docs site or a Binder notebook. The v4 API is a breaking change from v3, and existing scripts need migrating. There is a v4-migration guide and a convert module, which help but do not remove that work. Large runs are where friction will show: the docs include a performance explanation and a stuck-particles tutorial, which suggests memory, chunking and boundary handling take up much of users' time.