The vertical structure and development of the ENSO anomaly mode during 1979-1989

Abstract

The latest two Pacific basinwide warm episodes (1982-83 and 1986-87) exhibit some common features in their development and vertical structure. These features are examined by multivariate empirical orthogonal function analysis of the interannual variability of the ocean-atmosphere system along equatorial Indian and Pacific oceans. The updraft and downdraft branches of the anoamlous Walker circulation originate over the western Pacific and the eastern Indian Ocean, respectively. The early development of basinwide warming is characterized by the strengthening of a cross-equatorial low-level southerly component over the eastern Pacific and the enhancement of convection and boundary-layer westerlies over the western Pacific. It is possible that an individual ENSO event may result from different combinations of various sets of coupled processes, especially with regard to those that work in the eastern Pacific cold tongue and those in the western Pacific warm pool. -from Author