Editorial Type:
Article
Article Type:
Research Article

A Midlatitude Influence on Australian Monsoon Bursts

Sugata Narsey School of Earth, Atmosphere and Environment, and Australian Research Council Centre of Excellence for Climate Systems Science, Monash University, Clayton, Victoria, Australia

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Michael J. Reeder School of Earth, Atmosphere and Environment, and Australian Research Council Centre of Excellence for Climate Systems Science, Monash University, Clayton, Victoria, Australia

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Duncan Ackerley School of Earth, Atmosphere and Environment, and Australian Research Council Centre of Excellence for Climate Systems Science, Monash University, Clayton, Victoria, Australia

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Christian Jakob School of Earth, Atmosphere and Environment, and Australian Research Council Centre of Excellence for Climate Systems Science, Monash University, Clayton, Victoria, Australia

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Print Publication:
15 Jul 2017
DOI:
https://doi.org/10.1175/JCLI-D-16-0686.1
Page(s):
5377–5393
Restricted access

Abstract

The initiation of northern Australian monsoon rainfall bursts is accompanied by an increase in cyclonic circulation in the monsoon region. This study shows that the change in circulation at the start of the composite rainfall burst is predominantly influenced by midlatitude frontlike features. By exploiting the relationship between circulation tendency and the convergence of absolute vorticity flux, the circulation changes accompanying the initiation of Australian monsoon bursts is investigated. Moisture flux convergence is found to be proportional to the circulation changes in the monsoon region. Using a composite analysis it is shown that absolute vorticity fluxes through the southern boundary are by far the most important influence on monsoon burst circulation changes, with only one-third of events more closely related to other influences including the Madden–Julian oscillation. This is shown to be true throughout the wet season.

© 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Sugata Narsey, sugata.narsey@monash.edu

Abstract

The initiation of northern Australian monsoon rainfall bursts is accompanied by an increase in cyclonic circulation in the monsoon region. This study shows that the change in circulation at the start of the composite rainfall burst is predominantly influenced by midlatitude frontlike features. By exploiting the relationship between circulation tendency and the convergence of absolute vorticity flux, the circulation changes accompanying the initiation of Australian monsoon bursts is investigated. Moisture flux convergence is found to be proportional to the circulation changes in the monsoon region. Using a composite analysis it is shown that absolute vorticity fluxes through the southern boundary are by far the most important influence on monsoon burst circulation changes, with only one-third of events more closely related to other influences including the Madden–Julian oscillation. This is shown to be true throughout the wet season.

© 2017 American Meteorological Society. For information regarding reuse of this content and general copyright information, consult the AMS Copyright Policy (www.ametsoc.org/PUBSReuseLicenses).

Corresponding author: Sugata Narsey, sugata.narsey@monash.edu
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