Identification

Title

Decadal variability of Asian--Australian monsoon--ENSO-TBO relationships

Abstract

A set of dynamically coupled ocean-atmosphere mechanisms has previously been proposed for the Asia-Pacific tropics to produce a dominant biennial component of interannual variability [the tropospheric biennial oscillation (TBO)]. Namely, a strong Asian-Australian monsoon is often associated with negative SST anomalies in the equatorial eastern Pacific and a negative Indian Ocean dipole in northern fall between the strong Indian monsoon and strong Australian monsoon, and tends to be followed by a weak monsoon and positive SST anomalies in the Pacific the following year and so on. These connections are communicated through the large-scale east-west (Walker) circulation that involves the full depth of the troposphere. However, the Asia-Pacific climate system is characterized by intermittent decadal fluctuations whereby the TBO during some time periods is more pronounced than others. Observations and models are analyzed to identify processes that make the system less biennial at certain times due to one or some combination of the following: 1. increased latitudinal extent of Pacific trade winds and wider cold tongue; 2. warmer tropical Pacific compared to tropical Indian Ocean that weakens trade winds and reduces coupling strength; 3. eastward shift of the Walker circulation; 4. reduced interannual variability of Pacific and/or Indian Ocean SSTs. Decadal time-scale SST variability associated with the interdecadal Pacific oscillation (IPO) has been shown to alter the TBO over the Indo-Pacific region by contributing changes in either some or all of the four factors listed above. Analysis of a multicentury control run of the Community Climate System Model, version 4 (CCSM4), shows that this decadal modulation of interannual variability is transferred via the Walker circulation to the Asian-Australian monsoon region, thus affecting the TBO and monsoon-Pacific connections. Understanding these processes is important to be able to evaluate decadal predictions and longer-term climate change in the Asia-Pacific region.

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document

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http://n2t.net/ark:/85065/d7ww7jbx

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eng

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geoscientificInformation

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publication

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2016-01-01T00:00:00Z

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publication

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2011-09-15T00:00:00Z

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Copyright 2011 American Meteorological Society (AMS). Permission to use figures, tables, and brief excerpts from this work in scientific and educational works is hereby granted provided that the source is acknowledged. Any use of material in this work that is determined to be "fair use" under Section 107 or that satisfies the conditions specified in Section 108 of the U.S. Copyright Law (17 USC, as revised by P.L. 94-553) does not require the Society's permission. Republication, systematic reproduction, posting in electronic form on servers, or other uses of this material, except as exempted by the above statements, requires written permission or license from the AMS. Additional details are provided in the AMS Copyright Policies, available from the AMS at 617-227-2425 or amspubs@ametsoc.org. Permission to place a copy of this work on this server has been provided by the AMS. The AMS does not guarantee that the copy provided here is an accurate copy of the published work.

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OpenSky Support

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UCAR/NCAR - Library

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PO Box 3000

Boulder

80307-3000

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opensky@ucar.edu

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http://opensky.ucar.edu/

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