Impact of horizontal resolution on extended-range forecasts at ECMWF

The dataset of 30-day integrations with various model resolutions was used to evaluate model climate drift as a function of resolution. The zonal mean and eddy systematic errors show a strong dependence upon resolution. Some information about the initial conditions is retained almost throughout the integration time. There is a progressive loss of stationary and transient eddy activity. Both, the time-mean circulation and eddy activity are much weaker than observed in the tropics.