SLIMCAT model deployed on Leeds computer. SLIMCAT was a three-dimensional (3D) off-line chemical transport model (CTM). The model used winds and temperatures from meteorological analyses (e.g. from the UK Met Office or ECMWF) to specify the atmospheric transport and temperatures and calculates the abundances of chemical species in the troposphere and stratosphere. The model had the option of detailed chemical scheme(s) for the stratosphere and troposphere.

The model can be used to simulate the past and current atmosphere, help interpret observations, and to diagnose the extent of problems such as stratospheric ozone depletion or tropospheric pollution. This model was developed at the University of Leeds, UK.

== Introduction ==

Around 1995 Martyn Chipperfield (University of Leeds) wrote SLIMCAT. This was a stratosphere-only version of TOMCAT formulated on isentropic levels. At this time TOMCAT became a 'tropospheric' model and various people in Cambridge helped to add treatments of e.g. convection, boundary layer mixing, and tropospheric chemistry. Recently, SLIMCAT has been extended downwards to include the troposphere. As the two former models were so similar, it made maintenance/development easier to merge TOMCAT and SLIMCAT into a single library with a choice of vertical coordinate (and other things), so that one model covers all of the applications. Depending on the coordinate use, the model is still referred to as TOMCAT or SLIMCAT.

=== Key Details ===

- Variable resolution. Typical resolutions are 5 x 5 degrees for multiannual runs to up to 1 x 1 degree.
- Forced by meteorological analyses, usually ECMWF and sometimes UKMO.
-Options of detailed stratospheric or tropospheric chemistry schemes.
- Written in Fortran (f77, f90). Runs on most platforms (including vector machines). Parallelised using OpenMP and MPI.