Interdecadal variability in a global coupled model

Interdecadal variations are studied in a 325-year simulation performed by a coupled atmosphere, ocean general circulation model. The patterns obtained in this study describe some of the dominant features of interdecadal variations in the model atmosphere and in the model Pacific Ocean. (1)  Atmosphere . Interdecadal variations have no preferred time scale and can be generated by an AR(1)-process which has a longer characteristic time than that of the weather fluctuations. There are two dominant modes, one is related to variations of the tropical easterlies and the other to the Southern Hemisphere westerlies. The amplitude of the associated wind anomalies is largest in the upper troposphere. The associated temperature anomalies are in thermal-wind balance with the zonal winds and are out of phase in the troposphere and in the lower stratosphere. (2)  Pacific Ocean . The dominant mode in the Pacific is basin-wide with a time scale of 10 to 20 years. Its signature propagates westward in the tropics and then northward (southwestward) in the North (South) Pacific. The evolution is related to changes in the upper ocean circulation and the upper ocean thermal structure. In the midlatitudes, the current changes are in Sverdrup relation with the wind changes whereas in the tropics air–sea interaction processes might be involved during a certain phase of the oscillation. DOI: 10.1034/j.1600-0870.1994.t01-2-00007.x

[1]  David K. Salmon.  On interannual variability and climate change in the north Pacific , 1992 .

[2]  T. Nitta,et al.  Recent Warming of Tropical Sea Surface Temperature and Its Relationship to the Northern Hemisphere Circulation , 1989 .

[3]  P. James,et al.  Spatial Structure of Ultra-Low-Frequency Variability of the Flow In A Simple Atmospheric Circulation Model , 1992 .

[4]  Jin-Song Xu,et al.  The joint modes of the coupled atmosphere-ocean system observed from 1967 to 1986 , 1993 .

[5]  H. Storch,et al.  The Performance of Four Spectral GCMs in the Southern Hemisphere: The January and July Climatology and the Semiannual Wave , 1990 .

[6]  Ralph J. Slutz,et al.  A Comprehensive Ocean-Atmosphere Data Set , 1987 .

[7]  Uwe Mikolajewicz,et al.  Decadal variability of the North Atlantic in an ocean general circulation model , 1994 .

[8]  P. James,et al.  Ultra-low-frequency variability in a simple atmospheric circulation model , 1989, Nature.

[9]  R. Dickson,et al.  The great salinity anomaly in the northern North Atlantic 1968-1982 , 1988 .

[10]  Kevin E. Trenberth,et al.  Recent Observed Interdecadal Climate Changes in the Northern Hemisphere , 1990 .

[11]  K. Hasselmann.  PIPs and POPs: The reduction of complex dynamical systems using principal interaction and oscillation patterns , 1988 .

[12]  Robert Sausen,et al.  Time-dependent greenhouse warming computations with a coupled ocean-atmosphere model , 1992 .

[13]  R. A. Madden,et al.  Estimates of the Natural Variability of Time-Averaged Sea-Level Pressure , 1976 .

[14]  R. Sausen,et al.  Coupled ocean-atmosphere models with flux correction , 1988 .

[15]  Klaus Hasselmann,et al.  Mean Circulation of the Hamburg LSG OGCM and Its Sensitivity to the Thermohaline Surface Forcing , 1993 .