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Indian Ocean dipolelike variability in the CSIRO mark 3 coupled climate model


Cai, W and Hendon, HH and Meyers, GA, Indian Ocean dipolelike variability in the CSIRO mark 3 coupled climate model, Journal of Climate, 18, (10) pp. 1449-1468. ISSN 0894-8755 (2005) [Refereed Article]

DOI: doi:10.1175/JCLI3332.1


Coupled ocean-atmosphere variability in the tropical Indian Ocean is explored with a multicentury integration of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Mark 3 climate model, which runs without flux adjustment. Despite the presence of some common deficiencies in this type of coupled model, zonal dipolelike variability is produced. During July through November, the dominant mode of variability of sea surface temperature resembles the observed zonal dipole and has out-of-phase rainfall variations across the Indian Ocean basin, which are as large as those associated with the model El Niño-Southern Oscillation (ENSO). In the positive dipole phase, cold SST anomaly and suppressed rainfall south of the equator on the Sumatra-Java coast drives an anticyclonic circulation anomaly that is consisstent with the steady response (Gill model) to a heat sink displaced south of the equator. The northwest-southeast tilting Sumatra-Java coast results in cold sea surface temperature (SST) centered south of the equator, which forces anticylonic winds that are southeasterly along the coast, which thus produces local upwelling, coot SSTs, and promotes more anticylonic winds; on the equator, the easterlies raise the thermocline to the east via upwelling Kelvin waves and deepen the off-equatorial thermocline, to the west via off-equatorial downwelling Rossby waves. The model dipole mode exhibits little contemporaneous relationship with the model ENSO; however, this does not imply that it is independent of ENSO. The model dipole often (but not always) develops in the year following El Niño. It is triggered by an unrealistic transmission of the model's ENSO discharge phase through the Indonesian passages. In the model,the ENSO discharge Rossby waves arrive at the Sumatra-Java coast some 6 to 9 months after an El Niño peaks, causing the majority of model dipole events to peak in the year after an ENSO warm event. In the observed ENSO discharge, Rossby waves arrive at the Australian northwest coast. Thus the model Indian Ocean dipolelike variability is triggered by an unrealistic mechanism. The result highlights the importance of properly representing the transmission of Pacific Rossby waves and Indonesian throughflow in the complex topography of the Indonesian region in coupled climate models. © 2005 American Meteorological Society.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Physical oceanography
Objective Division:Environmental Policy, Climate Change and Natural Hazards
Objective Group:Adaptation to climate change
Objective Field:Social impacts of climate change and variability
UTAS Author:Meyers, GA (Professor Gary Meyers)
ID Code:45991
Year Published:2005
Web of Science® Times Cited:68
Deposited By:Centre for Marine Science
Deposited On:2007-08-01
Last Modified:2011-10-24

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