Hindcast ensembles are generated in baseline0 and baselinel through lagged initialization, meaning that the model initial state at the nominal start day (1 January of any given start year) is taken from the state a few days earlier or later.
Unfortunately, no robust improvement compared to the lagged initialization has been found; if there is improvement, this is compensated by additional problems such as an overestimation of the internal variability by the ensemble spread in some, though not all, variables (Marini et al.
1b,c), but the skill improvement by initialization has not increased against baseline1, except around Drake Passage and the Indian Ocean portion of the Southern Ocean (Figs.
But in a changing climate, model drift following initialization depends also on start year (Kharin et al.
Here, it is essential to use the atmospheric initialization as well as the high vertical resolution in the atmosphere for basic process representation (Pohlmann et al.
Placing a single global prediction system in the focus of a major research effort has demonstrated benefits such as the rapid development of alternative initialization strategies, sophisticated evaluation methods for quantities beyond the surface temperature, and regional applications of the global predictions.
1) We have not yet converged on a best initialization procedure of our prediction ensemble.
2012), a new control run with constant forcing to make sure the model simulates a stable climate, and a new ensemble of historical runs as a reference for assessing skill enhancement through initialization. Being tied to the general MPI-ESM development implies that the cycle of model versions rests outside of MiKlip's immediate control and occurs in intervals longer than sometimes desired by MiKlip.
For generational cycles of the prediction system that are defined not through different model versions but through different initialization procedures, a much faster turnover can be implemented.
Stammer, 2016: A comparison of two ensemble generation methods using oceanic singular vectors and atmospheric lagged initialization for decadal climate prediction.
Stammer, 2014: Impact of initialization procedures on the predictive skill of a coupled ocean-atmosphere model.