Decadal-scale climate variability in the tropical and North Pacific during the 1970s and 1980s: Observations and model results
- Scripps Institution of Oceanography, La Jolla, CA (United States)
An abrupt change in the large-scale boreal winter circulation pattern over the North Pacific was observed during the mid-1970s. This paper presents a variety of observed data and model results to describe the climate shift, and to understand some of the links within the coupled climate system that produced, it. Five main findings are emphasized: (1) evidence of abrupt, simultaneous, and apparently related changes can be found in many fields and in many model results; the climate shift is not an artifact, (2) over the tropical Pacific the climate change represents a shift in the state of the coupled ocean-atmosphere system, some aspects of which resemble features associated with El Nino episodes. However, the shift in state is not well characterized as due to a change in the frequency of intensity of El Nino episodes; it is better described as a change in background mean state, (3) When forced with observed SSTs, both a very simple atmospheric model and a full general circulation model (GCM) qualitatively simulate aspects of the decadalscale shift over the tropical Pacific, (4) when forced with observed surface wind stress, two ocean models of the tropical Pacific, in which surface heat fluxes are parameterized as Newtonian damping, reproduce some aspects of the near-equatorial decadal SST signal. However, the models do not reproduce the large changes in SST observed at higher latitudes of the tropical Pacific. suggesting that altered surface heat fluxes dominated in producing these changes, and (5) an important new finding of this study is the success of a GCM in reproducing important aspects of the observed mid-1970s shift in winter northern hemisphere circulation. Comparative analyses of the observed and GCM simulated circulation suggest the altered patterns of tropical Pacific SST and convection were important in forcing the changes in the mid-latitude circulation, a finding corroborated by recent GCM experiments. 70 refs., 18 figs.
- OSTI ID:
- 241228
- Journal Information:
- Climate Dynamics, Vol. 10, Issue 3; Other Information: PBD: Aug 1994
- Country of Publication:
- United States
- Language:
- English
Similar Records
Simulation of ENSO-like phenomena with a low-resolution coupled GCM of the global ocean and atmosphere
On the roles of tropical and midlatitude SSTs in forcing interannual to interdecadal variability in the winter northern hemisphere circulation