INSTABILITY OF THE OCEANIC WAVES IN THE TROPICAL REGION

In this paper,the effects of the large-scale mean sea temperature fields of the tropical ocean and the zonal current field (southern equatorial current) have been comprehensively entered in consideration on the basis of Chao and Ji (1985),and Ji and Chao (1986),the equatorial oceanic waves of the tropical ocean have been discussed by use of linearized primitive equations,then,the significant influence of the climatic background fields of the tropical ocean upon the oceanic waves of this region has been further testified.When very cold water appears in the tropical region,and the southern equatorial current is also relatively strong,the effect of the Rossby wave weakens,as a consequence,there are substitutive slow waves (i.e.thermal waves) which travel in opposite direction (eastward) to the Rossby wave.The characteristics of the slow wave are similar to those of Rossby waves,only the travelling direction is opposite.Under a certain environmental background field,the slow wave and the modified Rossby wave may be instable.With this conclusion,the mechanism of the occurrence,development and propagation of El Nino events has been studied.It is pointed out that the opposite travelling direction of the thermal wave and Rossby wave will bring repectively into action under different marine environmental background fields.The physical causes for that the abnormal warm water inclines to occur along the South American coast have also been explored in this paper.