IFS Documentation Part VIII: Atmospheric Composition

The simulation of greenhouse gases (GHG) and reactive trace gases and aerosol (COMPO) is a configurable extension of the IFS. These configurations are used in the operational forecast and reanalysis applications of the IFS for the Copernicus Atmosphere Monitoring Service (CAMS). This part of the documentation describes the simulation of the sink and source processes of atmospheric composition with the IFS as well as the specifics of the data assimilation approach for atmospheric composition.

The other parts of IFS documentation also cover tracer related aspects such as transport, radiation and data assimilation. In this part (8), authors will refer to the respective parts. The transport by advection is described in Part III Dynamics and Numerical Procedures. Only aspects specific to tracer advection such as the application of global mass fixers are covered in this part (8). The transport of tracers by turbulent diffusion and convection and the use of prognostic aerosols and ozone in the IFS radiation scheme are documented in Part IV Physical processes.

Atmospheric composition is simulated “on-line” in the IFS, i.e. together with the simulation of the dynamical and physical processes using the same data flow, methods and routines as applied for the meteorological tracers such as cloud water and humidity. This means that each forecast or analysis of the IFS with atmospheric composition also provides a meteorological forecast or analysis. The online approach enables a close coupling between meteorological and atmospheric composition processes. It also makes it possible to use the data assimilation capability of the IFS to assimilate atmospheric composition observations to correct the simulated concentrations