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Tropical rainfall, Rossby waves and regional winter climate predictions
Author(s) -
Scaife Adam A.,
Comer Ruth E.,
Dunstone Nick J.,
Knight Jeff R.,
Smith Doug M.,
MacLachlan Craig,
Martin Nicola,
Peterson K. Andrew,
Rowlands Dan,
Carroll Edward B.,
Belcher Stephen,
Slingo Julia
Publication year - 2016
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.2910
Subject(s) - predictability , climatology , extratropical cyclone , rossby wave , environmental science , equator , teleconnection , tropical wave , madden–julian oscillation , forcing (mathematics) , boreal , tropics , tropical cyclone , geology , geography , latitude , convection , el niño southern oscillation , meteorology , paleontology , physics , geodesy , quantum mechanics , fishery , biology
Skilful climate predictions of the winter North Atlantic Oscillation and Arctic Oscillation out to a few months ahead have recently been demonstrated, but the source of this predictability remains largely unknown. Here we investigate the role of the Tropics in this predictability. We show high levels of skill in tropical rainfall predictions, particularly over the Pacific but also the Indian and Atlantic Ocean basins. Rainfall fluctuations in these regions are associated with clear signatures in tropical and extratropical atmospheric circulation that are approximately symmetric about the Equator in boreal winter. We show how these patterns can be explained as steady poleward propagating linear Rossby waves emanating from just a few key source regions. These wave source ‘hotspots’ become more or less active as tropical rainfall varies from winter to winter but they do not change position. Finally, we show that predicted tropical rainfall explains a highly significant fraction of the predicted year‐to‐year variation of the winter North Atlantic Oscillation.