THE CLIMATE KELPIE BLOG: Teleconnections between climate drivers and regional climate, and model representation of links

Posted by eConnect on 15th July 2013

Research objective

Improve Australia’s dynamical forecasting by investigating the connection between several weather systems, including:

  • the Southern Oscillation Index
  • the Indian Ocean Dipole
  • the Madden-Julian Oscillation
  • the subtropical ridge
  • the Southern Annular Mode

Project duration

2010 – 2013

Outcomes

Cut-off lows and fronts are two of the most important weather systems for growing-season rainfall in south-east Australia. It is clear from this project that there is a more direct link between the remote climate drivers and the synoptic systems that produce rainfall.

Atmospheric blocking strongly affects cut-off lows, and ENSO and IOD influence southern Australian weather in winter and spring, via Rossby waves originating in the Indian Ocean. Climate models have difficulty representing blocking accurately; this mechanism is more complicated than previously understood.

Rossby waves spread energy eastwards and polewards to alter the strength of mid-latitude weather systems and, therefore, rainfall.

Climate models appear to generate only about half the number of cut-off lows that they should, because it is difficult to simulate atmospheric blocking. If models can accurately the effect of land–sea temperature differences both the sub-tropics and mid-latitudes, they do a better job of simulating atmospheric blocking.

POAMA’s representation of the Rossby wave teleconnection process is inaccurate. Its representation of this teleconnection pathway appears to have shifted to the east, which may help explain why skill is decreased in south-east Australia.

Climate models will benefit from improvements to:

  • representations of tropical Indian Ocean and atmosphere processes such as equatorial convection
  • atmosphere-ocean feedback necessary to sustain an independent IOD
  • land-surface temperature interaction with the atmosphere.

These advances will likely lead to a climate model with improved blocking, more cut-off lows and a more accurate representation of one of the key rainfall processes in the southern Australian region.

This project contributes to the long-term evolution of climate model skill, and seasonal forecasts are improving, benefiting all climate-sensitive sectors. Read the final report [PDF, 457 kB].

Research contact

Dr Peter McIntosh

Centre for Australian Weather and Climate Research

Peter.Mcintosh@csiro.au

Phone: 03 6232 5390

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