...
The current setup permits the nudging of the following 9 prognostic variables: Vorticity, divergence, temperature, surface pressure, specific humidity, ice water contents, liquid water contents, cloud fraction and stratospheric ozone. Dependent on the scientific objectives of the model experiment not all variables will require nudging. As a minimum it is recommended to use vorticity, divergence and temperature. In this context disk space usage should also be a consideration as an increasing number of nudged variables will result in larger forcing files. At T255L60 forcing files that contain all 9 variables require 70 MB for each time step (grid point file 47 MB, spectral file 23 MB).
Relaxation
...
coefficients
As a standard all relaxation coefficients are initially set to 0.5 which represents a relatively "tight" nudging to the external data. These values should be adjusted according to the objectives of the experiment. Frequently the best results are obtained with different relaxation coefficients specific to each nudged variable. The external analysis data is updated every six hours and the model linearly interpolates in time between these data points. A too tight nudging can result in unrealistic behaviour in the freely calculated model variables.
...