OCEAN ATMOSPHERE INTERACTIONS IN LOW-LATITUDE AUSTRALASIA

An analysis of ocean‐atmosphere interactions in low‐latitude Australasia is undertaken using simultaneous and lagged cross correlations and with reference to specific El NiñTo/Southern Oscillation (ENSO) and anti‐ENSO episodes during the period 1964–1983. Major emphasis is placed on the relative importance of wind‐stress‐sea‐surface‐temperature (SST) mechanisms and cloudiness‐radiation mechanisms, and the possible influence of SST advection, oceanic mixing, Indonesian throughflow, and low‐frequency forcings on ocean‐atmosphere couplings in the region. The evolution of ENSO events in Australasia is usually marked by a distinct alternation from anti‐ENSO to ENSO conditions. Ocean‐atmosphere dynamics, involving primarily wind and radiative forcings, have been seen to be linked to such developments. However, SST advection and oceanic mixing are also found to play integral roles in forcing and feedback processes. Thus anti‐ENSO (ENSO) events are marked by easterly (westerly) wind‐stress anomalies in the western equatorial Pacific, southerly (northerly) wind‐stress anomalies in eastern Indonesian and eastern Coral Sea regions, +(−)SST anomalies and weak (strong) SST advection in northern Australian waters, positive (negative) cloudiness anomalies over Australasia and high (low) sea‐level anomalies at southern Philippine and northern Australian stations. There are also indications that ENSO‐like conditions can develop in Australasia with no apparent events in the wider Pacific basin. However, there seems to be no conclusive evidence for the influence of oceanic throughflow on ocean‐atmosphere interactions, and thus ENSO or anti‐ENSO phases. Nevertheless, there are indications that Indonesian throughflow is modulated by remote low‐frequency forcings that are also apparent in SST anomalies in northern Australian waters. The potential for precursors of ENSO and anti‐ENSO events in the Australasian region is high. All of the parameters examined in this study show significant lead/lag correlations, with the strongest persistence generally centering on the Southern Hemisphere winter‐spring period. However, further investigation of potential and suggested links with coherent precipitation patterns over the region is still required. Moreover, any future developments in our understanding of ocean–atmosphere interactions in Australasia will need to address the general problem of establishing and maintaining extensive data networks. Copyright © 1990 John Wiley & Sons, Ltd