TM5 — Tracer Model, version 5
#############################################

Overview
========

TM5 is an offline global atmospheric chemistry and transport model developed
at KNMI and IMAU (Utrecht University) and widely used by the atmospheric
inversion community.  It transports chemical species and aerosols using
meteorological fields pre-computed by an external model (typically ECMWF ERA5
or operational analyses).

TM5 supports a two-way nested zoom capability that allows high horizontal
resolution over a region of interest while maintaining a coarser global domain,
making it particularly suitable for regional GHG inversion studies.

Key references
==============

* **Krol et al. (2005)** — the original TM5 description:
  *The two-way nested global chemistry-transport zoom model TM5: algorithm and
  applications*, Atmos. Chem. Phys., 5, 417–432,
  `doi:10.5194/acp-5-417-2005 <https://doi.org/10.5194/acp-5-417-2005>`__.

* **Huijnen et al. (2010)** — the chemistry module:
  *The global chemistry transport model TM5: description and evaluation of the
  tropospheric chemistry version 3.0*, Geosci. Model Dev., 3, 445–473,
  `doi:10.5194/gmd-3-445-2010 <https://doi.org/10.5194/gmd-3-445-2010>`__.

Official resources
==================

* `TM5 project page (KNMI) <https://www.projects.science.uu.nl/tm5/>`__
* `TM5-4DVar inversion system <https://tm5.sourceforge.io/>`__
* `Source code repository (Subversion) <https://sourceforge.net/projects/tm5/>`__

CIF integration
===============

The CIF TM5 plugin is located under
:doc:`pycif.plugins.models.TM5 </documentation/plugins/models/TM5>`.
It interfaces TM5 as an offline transport model for tracer inversions.

Model sources compatible with CIF are available under ``model_sources/TM5/``
in the CIF repository.  These sources are based on the TM5 release maintained
at IMAU/KNMI and have been adapted to expose the model state to the CIF
observation operator.

.. note::

    The TM5 plugin is used primarily for global CH₄ inversions within CIF.
    It has been integrated and validated at CSC Finland (FMI) in the context
    of the VERIFY and EYE-CLIMA projects.