Does increased atmospheric resolution improve seasonal climate predictions
2019
We assess the impact of atmospheric horizontal resolution on the prediction skill
and fidelity of seasonal forecasts. We show the response to an increase of atmospheric resolution from 0.8 to 0.3⁰ horizontal grid spacing in parallel ensembles of
forecasts. Changes in the prediction skill of major modes of tropical El Nino Southern Oscillation (ENSO) and extratropical North Atlantic Oscillation (NAO) variability are small and not detected and there is no discernible impact on the weak
signal-to-noise ratio in seasonal predictions of the winter NAO at this range of resolutions. Although studies have shown improvements in the simulation of tropical
cyclones as model resolution is increased, we find little impact on seasonal prediction skill of either their numbers or intensity. Over this range of resolutions it
appears that the benefit of increasing atmospheric resolution to seasonal climate
predictions is minimal. However, at yet finer scales there appears to be increased
eddy feedback which could strengthen weak signals in predictions of the NAO.
Until prediction systems can be run operationally at these scales, it may be better to
use additional computing resources for other enhancements such as increased
ensemble size, for which there is a clear benefit in extratropical seasonal prediction
skill.
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