General Description: Model basic design

see also: dynamics and numerics | initial and boundary conditions | physical parameterizations | external parameters | code and parallelization | data assimilation
Last updated: September 2011

The nonhydrostatic fully compressible COSMO-Model has been developed to meet high-resolution regional forecast requirements of weather services and to provide a flexible tool for various scientific applications on a broad range of spatial scales. It has been designed for meso-β and meso-γ scales where nonhydrostatic effects begin to play an essential role in the evolution of atmospheric flows.

By employing 1 to 3 km grid spacing for operational forecasts over a large domain, it is expected that deep moist convection and the associated feedback mechanisms to the larger scales of motion can be explicitly resolved. Meso-γ scale NWP-models thus have the principle potential to overcome the shortcomings resulting from the application of parameterized convection in current coarse-grid hydrostatic models. In addition, the impact of topography on the organization of penetrative convection by, e.g. channeling effects, is represented much more realistically in high resolution nonhydrostatic forecast models.

The initial operational applications of the model within COSMO were mainly on the meso-β scale using a grid spacing of about 7 km. The key issue then was an accurate numerical prediction of near-surface weather conditions, focusing on clouds, fog, frontal precipitation, and orographically and thermally forced local wind systems. In 2007 / 2008, several partners started to run meso-γ scale versions by employing a grid spacing between 2 and 3 km. Now the focus is on a direct simulation of severe weather events triggered by deep moist convection, such as supercell thunderstorms, intense mesoscale convective complexes, prefrontal squall-line storms and heavy snowfall from wintertime mesocyclones.

Besides the operational application, the COSMO-Model provides a nonhydrostatic modelling framework for various scientific and technical purposes. Outstanding applications are

Such a wide range of applications imposes a number of requirements for the physical, numerical and technical design of the model. The main design requirements are:

The development of the COSMO-Model was organized along these basic guidelines. However, not all of the requirements are fully implemented, and development work and further improvement is an ongoing task. The main features and characteristics of the present release are summarized below.