While sea surface temperature (SST) anomalies in the eastern equatorial Pacific are dominated by the thermocline feedback, in the central equatorial Pacific local wind effects, such as zonal advection, are important as well. El Niño-Southern Oscillation (ENSO) simulations with a linear model improve markedly if these effects are included as a local wind stress feedback on SST. An atmosphere model that reacts both to eastern and central Pacific SST anomalies is needed for producing a realistic ENSO cycle.

First, simulations are studied of a linear 1.5-layer reduced-gravity ocean model and a linear SST anomaly equation, forced by observed monthly wind stress. If only the thermocline feedback is present in the SST equation, SST can be simulated well in the eastern Pacific, but, contrary to observations, central Pacific SST is out of phase with the eastern Pacific. If a wind stress feedback is added in the SST equation, as a term proportional to the zonal wind stress, correlations between observed and simulated SST are above 0.8 in both the central and eastern Pacific, and the correlation between the Niño-3 (5°S-5°N, 90°-150°W) and Niño-4 (5°S-5°N, 150°W-160°E) indexes is close to the observed value of 0.75.