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The effect of doubled CO 2 and model basic state biases on the monsoon‐ENSO system. II: Changing ENSO regimes
Author(s) -
Turner A. G.,
Inness P. M.,
Slingo J. M.
Publication year - 2007
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.83
Subject(s) - climatology , forcing (mathematics) , monsoon , el niño southern oscillation , climate model , environmental science , troposphere , oscillation (cell signaling) , monsoon of south asia , east asian monsoon , atmospheric sciences , flux (metallurgy) , climate change , geology , oceanography , materials science , biology , metallurgy , genetics
Integrations of a fully‐coupled climate model with and without flux adjustments in the equatorial oceans are performed under 2 × CO 2 conditions to explore in more detail the impact of increased greenhouse gas forcing on the monsoon‐ENSO system. When flux adjustments are used to correct some systematic model biases, ENSO behaviour in the modelled future climate features distinct irregular and periodic (biennial) regimes. Comparison with the observed record yields some consistency with ENSO modes primarily based on air‐sea interaction and those dependent on basinwide ocean wave dynamics. Simple theory is also used to draw analogies between the regimes and irregular (stochastically forced) and self‐excited oscillations respectively. Periodic behaviour is also found in the Asian‐Australian monsoon system, part of an overall biennial tendency of the model under these conditions related to strong monsoon forcing and increased coupling between the Indian and Pacific Oceans. The tropospheric biennial oscillation (TBO) thus serves as a useful descriptor for the coupled monsoon‐ENSO system in this case. The presence of obvious regime changes in the monsoon‐ENSO system on interdecadal timescales, when using flux adjustments, suggests there may be greater uncertainty in projections of future climate, although further modelling studies are required to confirm the realism and cause of such changes. Copyright © 2007 Royal Meteorological Society