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Zusammenfassung:
We present the evaluation of temperature and precipitation forecasts obtained with the MiKlip decadal
climate prediction system. These decadal hindcast experiments are verified with respect to the accuracy of the
ensemble mean and the ensemble spread as a representative for the forecast uncertainty. The skill assessment
follows the verification framework already used by the decadal prediction community, but enhanced with
additional evaluation techniques like the logarithmic ensemble spread score. The core of the MiKlip system
is the coupled Max Planck Institute Earth System Model. An ensemble of 10 members is initialized annually
with ocean and atmosphere reanalyses of the European Centre for Medium-Range Weather Forecasts. For
assessing the effect of the initialization, we compare these predictions to uninitialized climate projections
with the same model system. Initialization improves the accuracy of temperature and precipitation forecasts
in year 1, particularly in the Pacific region. The ensemble spread well represents the forecast uncertainty in
lead year 1, except in the tropics. This estimate of prediction skill creates confidence in the respective 2014
forecasts, which depict less precipitation in the tropics and a warming almost everywhere. However, large
cooling patterns appear in the Northern Hemisphere, the Pacific South America and the Southern Ocean.
Forecasts for 2015 to 2022 show even warmer temperatures than for 2014, especially over the continents. The
evaluation of lead years 2 to 9 for temperature shows skill globally with the exception of the eastern Pacific.
The ensemble spread can again be used as an estimate of the forecast uncertainty in many regions: It improves
over the tropics compared to lead year 1. Due to a reduction of the conditional bias, the decadal predictions of
the initialized system gain skill in the accuracy compared to the uninitialized simulations in the lead years 2
to 9. Furthermore, we show that increasing the ensemble size improves the MiKlip decadal climate prediction
system for all lead years.
