The seasonal cycle in coupled ocean-atmosphere general circulation models

Covey, C. and Abe-Ouchi, A. and Boer, G. J. and Boville, B. A. and Cubasch, U. and Fairhead, L. and Flato, G. M. and Gordon, H. and Guilyardi, E. and Jiang, X. and Johns, T. C. and Le Treut, H. and Madec, G. and Meehl, G. A. and Miller, R. and Noda, A. and Power, S. B. and Roeckner, E. and Russell, G. and Schneider, E. K. and Stouffer, J. R. and Terray, L. and von Storch, J.-S. (2000) The seasonal cycle in coupled ocean-atmosphere general circulation models. Climate Dynamics, 16 (10-11). pp. 775-787. ISSN 0930-7575


Abstract

We examine the seasonal cycle of near-surface air temperature simulated by 17 coupled ocean-atmosphere general circulation models participating in the Coupled Model Intercomparison Project (CMIP). Nine of the models use ad hoc 'flux adjustment' at the ocean surface to bring model simulations close to observations of the present-day climate. We group flux-adjusted and non-flux-adjusted models separately and examine the behavior of each class. When averaged over all of the flux-adjusted model simulations, near-surface air temperature falls within 2 K of observed values over the oceans. The corresponding average over non-flux-adjusted models shows errors up to 6 K in extensive ocean areas. Flux adjustments are not directly applied over land, and near-surface land temperature errors are substantial in the average over flux-adjusted models, which systematically underestimates (by 5 K) temperature in areas of elevated terrain. The corresponding average over non-flux-adjusted models forms a similar error pattern (with somewhat increased amplitude) over land. We use the temperature difference between July and January to measure seasonal cycle amplitude. Zonal means of this quantity from the individual flux-adjusted models form a fairly tight cluster (all within 30% of the mean) centered on the observed values. The non-flux-adjusted models perform nearly as well at most latitudes. In Southern Ocean mid-latitudes, however, the non-flux-adjusted models overestimate the magnitude of January-minus-July temperature differences by 5 K due to an overestimate of summer (January) near-surface temperature. This error is common to five of the eight non-flux-adjusted models. Also, over Northern Hemisphere mid-latitude land areas, zonal mean differences between July and January temperatures simulated by the non-flux-adjusted models show a greater spread (positive and negative) about observed values than results from the flux-adjusted models. Elsewhere, differences between the two classes of models are less obvious. At no latitude is the zonal mean difference between averages over the two classes of models greater than the standard deviation over models. The ability of coupled GCMs to simulate a reasonable seasonal cycle is a necessary condition for confidence in their prediction of long-term climatic changes (such as global warming), but it is not a sufficient condition unless the seasonal cycle and long-term changes involve similar climatic processes. To test this possible connection, we compare seasonal cycle amplitude with equilibrium warming under doubled atmospheric carbon dioxide for the models in our data base. A small but positive correlation exists between these two quantities. This result is predicted by a simple conceptual model of the climate system, and it is consistent with other modeling experience, which indicates that the seasonal cycle depends only weakly on climate sensitivity.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 05 Jan 2022 04:17
Last Modified: 18 Feb 2022 05:48
Uncontrolled Keywords: surface air-temperature; spatial variability; climate sensitivity; CO2; increase; project; layer
Fields of Research (2008): 04 Earth Sciences > 0401 Atmospheric Sciences > 040105 Climatology (excl.Climate Change Processes)
Fields of Research (2020): 37 EARTH SCIENCES > 3702 Climate change science > 370202 Climatology
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9603 Climate and Climate Change > 960303 Climate Change Models
D Environment > 96 Environment > 9603 Climate and Climate Change > 960304 Climate Variability (excl. Social Impacts)
Socio-Economic Objectives (2020): 19 ENVIRONMENTAL POLICY, CLIMATE CHANGE AND NATURAL HAZARDS > 1905 Understanding climate change > 190502 Climate variability (excl. social impacts)
Identification Number or DOI: https://doi.org/10.1007/s003820000081
URI: http://eprints.usq.edu.au/id/eprint/44880

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