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Abstract:
We show that fluctuations in atmospheric angular momentum and the length of day are predictable out to more than a year ahead, that this provides an atmospheric source of long-range predictability of surface climate and that it has important implications for our understanding of climate variability. We use ensemble climate predictions to demonstrate long-range predictability of signals in the atmospheric angular momentum field that propagate slowly and coherently polewards due to wave–mean flow interaction within the atmosphere. These predictable signals are shown to precede changes in extratropical climate via the North Atlantic Oscillation and the extratropical jet stream. Our results extend the lead time for length-of-day predictions, demonstrate a source of long-range predictability from within the atmosphere and illustrate a clear link between geodesy and climate prediction. Finally, we will show that our results also lead to an important new insight into climate teleconnections.
