Recent advances in computer power and climate modeling capability have provided the opportunity for several modeling groups to undertake extended integrations with global coupled ocean-atmosphere climate models that allow the study of coupled processes thought to be important in producing Southern Oscillation and El Niño phenomena. Results are shown here from such a coupled model, developed at the National Center for Atmospheric Research (NCAR), that consists of a global, spectral (R15) atmospheric general circulation model (GCM) coupled to a global, 5° latitude-longitude, four-layer, ocean GCM. In spite of limitations of the coarse model grid, Southern Oscillation-type interannual variability of the ocean-atmosphere system is inherent in the coupled model. One of the mysteries of the Southern Oscillation cycle is how the system makes the transition from cold to warm phase and back again in the tropical Pacific in northern spring. Evidence is shown from the NCAR coupled model that a modulation of... Abstract Recent advances in computer power and climate modeling capability have provided the opportunity for several modeling groups to undertake extended integrations with global coupled ocean-atmosphere climate models that allow the study of coupled processes thought to be important in producing Southern Oscillation and El Niño phenomena. Results are shown here from such a coupled model, developed at the National Center for Atmospheric Research (NCAR), that consists of a global, spectral (R15) atmospheric general circulation model (GCM) coupled to a global, 5° latitude-longitude, four-layer, ocean GCM. In spite of limitations of the coarse model grid, Southern Oscillation-type interannual variability of the ocean-atmosphere system is inherent in the coupled model. One of the mysteries of the Southern Oscillation cycle is how the system makes the transition from cold to warm phase and back again in the tropical Pacific in northern spring. Evidence is shown from the NCAR coupled model that a modulation of...