Newtonian Relaxation

OpenIFS uses initial and boundary conditions to calculate its own model dynamics, i.e. meteorological variables that are resolved on the grid scale. Newtonian relaxation, here referred to as "nudging", is a simple form of data assimilation which allows to constrain or force the model's meteorological fields with reanalysis data. This can be useful for instance in sensitivity studies which aim to isolate model physics or model chemistry without feedbacks on the dynamics.

In this article we explain how to prepare and configure the model for a nudged simulation. Therein the model will read in meteorological parameters at the grid scale from pre-computed external forcing files.