Teleconnection Pathways of ENSO and the IOD and the Mechanisms for Impacts on Australian Rainfall

Author:

Cai Wenju1,van Rensch Peter1,Cowan Tim1,Hendon Harry H.2

Affiliation:

1. CSIRO Wealth from Oceans National Research Flagship, and CSIRO Water for a Healthy Country Flagship, Aspendale, Victoria, Australia

2. Centre for Australian Weather and Climate Research, Bureau of Meteorology, Melbourne, Australia

Abstract

Abstract Impacts of El Niño–Southern Oscillation (ENSO) and the Indian Ocean dipole (IOD) on Australian rainfall are diagnosed from the perspective of tropical and extratropical teleconnections triggered by tropical sea surface temperature (SST) variations. The tropical teleconnection is understood as the equatorially trapped, deep baroclinic response to the diabatic (convective) heating anomalies induced by the tropical SST anomalies. These diabatic heating anomalies also excite equivalent barotropic Rossby wave trains that propagate into the extratropics. The main direct tropical teleconnection during ENSO is the Southern Oscillation (SO), whose impact on Australian rainfall is argued to be mainly confined to near-tropical portions of eastern Australia. Rainfall is suppressed during El Niño because near-tropical eastern Australia directly experiences subsidence and higher surface pressure associated with the western pole of the SO. Impacts on extratropical Australian rainfall during El Niño are argued to stem primarily from the Rossby wave trains forced by convective variations in the Indian Ocean, for which the IOD is a primary source of variability. These equivalent-barotropic Rossby wave trains emanating from the Indian Ocean induce changes to the midlatitude westerlies across southern Australia, thereby affecting rainfall through changes in mean-state baroclinicity, west–east steering, and possibly orographic effects. Although the IOD does not mature until austral spring, its impact on Australian rainfall during winter is also ascribed to this mechanism. Because ENSO is largely unrelated to the IOD during austral winter, there is limited impact of ENSO on rainfall across southern latitudes of Australia in winter. A strong impact of ENSO on southern Australia rainfall in spring is ascribed to the strong covariation of ENSO and the IOD in this season. Implications of this pathway from the tropical Indian Ocean for impacts of both the IOD and ENSO on southern Australian climate are discussed with regard to the ability to make seasonal climate predictions and with regard to the role of trends in tropical SST for driving trends in Australian climate.

Publisher

American Meteorological Society

Subject

Atmospheric Science

Reference38 articles.

1. Influence of the Indian Ocean Dipole on the Australian winter rainfall;Ashok;Geophys. Res. Lett.,2003

2. Dynamics of late autumn rainfall reduction over southeastern Australia;Cai;Geophys. Res. Lett.,2008

3. Positive Indian Ocean Dipole events precondition southeast Australia bushfires;Cai;Geophys. Res. Lett.,2009

4. Recent unprecedented skewness towards positive Indian Ocean Dipole occurrences and its impact on Australian rainfall;Cai;Geophys. Res. Lett.,2009

5. Argo profiles a rare occurrence of three consecutive positive Indian Ocean Dipole events, 2006–2008;Cai;Geophys. Res. Lett.,2009

同舟云学术

1.学者识别学者识别

2.学术分析学术分析

3.人才评估人才评估

"同舟云学术"是以全球学者为主线,采集、加工和组织学术论文而形成的新型学术文献查询和分析系统,可以对全球学者进行文献检索和人才价值评估。用户可以通过关注某些学科领域的顶尖人物而持续追踪该领域的学科进展和研究前沿。经过近期的数据扩容,当前同舟云学术共收录了国内外主流学术期刊6万余种,收集的期刊论文及会议论文总量共计约1.5亿篇,并以每天添加12000余篇中外论文的速度递增。我们也可以为用户提供个性化、定制化的学者数据。欢迎来电咨询!咨询电话:010-8811{复制后删除}0370

www.globalauthorid.com

TOP

Copyright © 2019-2024 北京同舟云网络信息技术有限公司
京公网安备11010802033243号  京ICP备18003416号-3