ENSO Predictions with Coupled Ocean Atmosphere Models

Abstract

The strongest signal on the short range climatic time scale, ranging from a few months to several years, is the El Nino/Southern Oscillation Phenomenon (ENSO). It is characterized by a weakening of the trade winds along the equator and a huge redistribution of heat from the western to the eastern tropical Pacific. The impacts of ENSO are felt worldwide through a disruption of the atmospheric general circulation pattern (Ropelewski and Halpert 1987), which leads, for instance, to severe droughts in Northwest Australia and South East Asia during an El Nino event. The Northeast region of Brazil and Zimbabwe are other regions where rainfall variations are highly correlated with ENSO indices and there are many other examples. Off the Peruvian coast, the marine ecosystem is directly affected by the oceanic variations in upwelling, which has a large impact on the fishery industry. For all these regions, reliable ENSO forecasts would offer decision-makers an opportunity to take account of anticipated climate variations, in order to reduce impacts of ENSO on the economy. Thus, it is a logical consequence that the study of ENSO predictability has become a field of major research.