Recent observations pointed out that there is a strong biennial component in the El Nino Southern Oscillation (ENSO) which is closely related to the mean seasonal cycle. The major objective of this program is to design and test a hierarchy of simple coupled air-sea models to address the presumption that the biennial oscillation needs to be accounted for, in order to better predict the ENSO phenomena. The plan is to develop a hierarchy of models that will end with an intermediate ENSO coupled atmosphere-ocean model which will have interannual variability related to seasonal variability as observed. The models will be validated against available observations. Two processes will be examined to determine the validity of the models: the effect of evaporation on SST and the influence of monsoonal cycle of convection and winds on interannual variability.
