The influence of relaxation of the trade winds on the baroclinic wave in equatorial eastern and western Pacific Ocean

In general, El Nio refers to the appearance of unusual high sea-surface temperature in the eastern tropical Pacific Ocean. But in recent El Nio events (for example, 1982/1983 and 1986/1987), the warm sea surface temperature anomaly first appears in the western Pacific Ocean and then expands eastward. That is to say, the El Nio events are not only confined to the eastern tropical Pacific Ocean. Based on the above facts, a baroclinic two-layers ocean model is developed and used to study the responding characteristics of equatorial eastern and western Pacific Ocean to relaxation of trade winds. The results show the responding features are different due to the different physical processes off the coast of the eastern and western Pacific Ocean. In the western Pacific Ocean, when the westward trade winds relax, a eastward propagating wave quickly develops. At the same time, a westward traveling wave also excites in the eastern Pacific Ocean, but no matter how the speed and amplitude, the eastward propagating wave is bigger than the westward traveling one, the eastward wave can rapidly affect on the central part of the Pacific Ocean, i.e., the western Pacific Ocean is easy to be the source of El Nio events, especially the strong El Nio events.