Overview: What is LMDZ-SACS?#
LMDZ-SACS is an offline tracer transport model, with forward, tangent linear and adjoint codes, derived from the global circulation model (GCM) LMDZ for the regular grid version and from DYNAMICO , the new dynamical core for LMDZ for the unstructured icosahedral grid. The model is coupled with the SACS linear chemistry module.
Official resources#
Key references:
Hourdin et al. (2006) — LMDZ4 dynamical core: The LMDZ4 general circulation model: climate performance and sensitivity to parametrized physics with emphasis on tropical convection, Clim. Dyn., 27, 787–813, doi:10.1007/s00382-006-0158-0.
Chevallier et al. (2005) — TL/adjoint transport model derived from LMDZ: Inferring CO₂ sources and sinks from satellite observations: Method and application to TOVS data, J. Geophys. Res., 110, D24309, doi:10.1029/2005JD006390.
The model grids#
LMDZ-SACS can be used on two types of grid, both at several resolutions (horizontal and vertical)
The regular latitude longitude grid, composed of square cells with smaller areas at high latitudes
The unstructured icosahedral grid, composed of hexagonal cells of similar area
Time resolution#
A LMDZ-SACS simulation is always one month long, from the first day of the month to the last day of the month. Most of the dynamics and physics variables are computed once for all ahead of time with the full GCM averaged every 3 hours then saved to disk. LMDZ-SACS reads these 3 hourly variables, called mass fluxes, from disk to compute the tracer transport.
Code parallelisation#
LMDS-SACS code is parallelized with OpenACC compiler directives (similar to OpenMP directive), to be compiled for use on GPU, but can also be compiled for use on multicore CPU with some compilers.