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The seasonal cycle of blocking and associated physical mechanisms in the Australian region and relationship with rainfall

Citation

Pook, MJ and Risbey, JS and McIntosh, PC and Ummenhofer, CC and Marshall, AG and Meyers, GA, The seasonal cycle of blocking and associated physical mechanisms in the Australian region and relationship with rainfall, Monthly Weather Review, 141, (12) pp. 4534-4553. ISSN 0027-0644 (2013) [Refereed Article]


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DOI: doi:10.1175/MWR-D-13-00040.1

Abstract

The seasonal cycle of blocking in the Australian region is shown to be associated with major seasonal temperature changes over continental Antarctica (approximately 15-35C) and Australia (about 8-17C) and with minor changes over the surrounding oceans (below 5C). These changes are superimposed on a favorable background state for blocking in the region resulting from a conjunction of physical influences. These include the geographical configuration and topography of the Australian and Antarctic continents and the positive west to east gradient of sea surface temperature in the Indo-Australian sector of the Southern Ocean. Blocking is represented by a blocking index (BI) developed by the Australian Bureau of Meteorology. The BI has a marked seasonal cycle that reflects seasonal changes in the strength of the westerly winds in the midtroposphere at selected latitudes. Significant correlations between the BI at Australian longitudes and rainfall have been demonstrated in southern and central Australia for the austral autumn, winter, and spring. Patchy positive correlations are evident in the south during summer but significant negative correlations are apparent in the central tropical north. By decomposing the rainfall into its contributions from identifiable synoptic types during the April-October growing season, it is shown that the high correlation between blocking and rainfall in southern Australia is explained by the component of rainfall associated with cutoff lows. These systems form the cyclonic components of blocking dipoles. In contrast, there is no significant correlation between the BI and rainfall from Southern Ocean fronts.

Item Details

Item Type:Refereed Article
Keywords:mathematical models, meteorology, bureau of meteorologies, negative correlation, physical mechanism, positive correlations, sea surface temperature (SST), seasonal changes, seasonal temperature changes, Southern ocean
Research Division:Earth Sciences
Research Group:Atmospheric Sciences
Research Field:Meteorology
Objective Division:Environment
Objective Group:Atmosphere and Weather
Objective Field:Weather
Author:Pook, MJ (Dr Michael Pook)
Author:Risbey, JS (Dr James Risbey)
Author:McIntosh, PC (Dr Peter McIntosh)
ID Code:119090
Year Published:2013
Web of Science® Times Cited:16
Deposited By:Centre for Ecology and Biodiversity
Deposited On:2017-07-26
Last Modified:2017-10-16
Downloads:23 View Download Statistics

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