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On the dynamics of persistent states and their secular trends in the waveguides of the Southern Hemisphere troposphere


O'Kane, TJ and Risbey, JS and Monselesan, DP and Horenko, I and Franzke, CLE, On the dynamics of persistent states and their secular trends in the waveguides of the Southern Hemisphere troposphere, Climate Dynamics, 46, (11-12) pp. 3567-3597. ISSN 0930-7575 (2016) [Refereed Article]

Copyright Statement

Copyright 2015 Springer-Verlag Berlin Heidelberg

DOI: doi:10.1007/s00382-015-2786-8


We identify the dynamical drivers of systematic changes in persistent quasi-stationary states (regimes) of the Southern Hemisphere troposphere and their secular trends. We apply a purely data-driven approach, whereby a multiscale approximation to nonstationary dynamical processes is achieved through optimal sequences of locally stationary fast vector autoregressive factor processes, to examine a high resolution atmospheric reanalysis over the period encompassing 1958–2013. This approach identifies regimes and their secular trends in terms of the predictability of the flow and is Granger causal. A comprehensive set of diagnostics on both isentropic and isobaric surfaces is employed to examine teleconnections over the full hemisphere and for a set of regional domains. Composite states for the hemisphere obtained from nonstationary nonparametric cluster analysis reveal patterns consistent with a circumglobal wave 3 (polar)–wave 5 (subtropical) pattern, while regional composites reveal the Pacific South American pattern and blocking modes. The respective roles of potential vorticity sources, stationary Rossby waves and baroclinic instability on the dynamics of these circulation modes are shown to be reflected by the seasonal variations of the waveguides, where Rossby wave sources and baroclinic disturbances are largely contained within the waveguides and with little direct evidence of sustained remote tropical influences on persistent synoptic features. Warm surface temperature anomalies are strongly connected with regions of upper level divergence and anticyclonic Rossby wave sources. The persistent states identified reveal significant variability on interannual to decadal time scales with large secular trends identified in all sectors apart from a region close to South America.

Item Details

Item Type:Refereed Article
Keywords:atmospheric teleconnections, baroclinic instability, Rossby waves, waveglides, regimes, secular trends
Research Division:Earth Sciences
Research Group:Climate change science
Research Field:Climatology
Objective Division:Environmental Management
Objective Group:Air quality, atmosphere and weather
Objective Field:Atmospheric processes and dynamics
UTAS Author:O'Kane, TJ (Dr Terry O'Kane)
UTAS Author:Risbey, JS (Dr James Risbey)
ID Code:118384
Year Published:2016
Web of Science® Times Cited:33
Deposited By:Directorate
Deposited On:2017-07-11
Last Modified:2017-10-17

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