Multi-scale convective systems during the initial phase of the 1986/87 EL Niño

Abstract

Temporal and spatial characteristics of tropical convective systems and their associated atmospheric circulations such as intraseasonal variations (ISV), super cloud clusters (SCC), twin cyclones and westerly wind bursts (WWB) developed during the initial phase of the 1986/87 El Niño are investigated. Most ISVs originated in the Indian Ocean and propagated eastward through the western Pacific and consisted of SCCs, twin cyclones and WWBs. Time evolution and horizontal-vertical structure of major ISVs in 1986, which appeared to play an important role in the El Niño development, such as (1) twin cyclone in May, (2) severely enhanced ITCZ in August and (3) SCC in November which brought about a major El Niño development, are analyzed in detail. It is suggested that the WWBs associated with the SCCs propagating eastward along the equator from the Indian Ocean toward the western Pacific region are blocked by the surface topography over the "maritime continent", especially over Sumatra.