Indian Ocean Climate Initiative - Western Australia

Project 1.1: Detection and Attribution of Changes to Weather Systems and Large Scale Circulation Drivers (Carsten Frederiksen, Jorgen Frederiksen and Meelis Zidikeri)

Planned outcomes:

• Identify and document observed changes in the mean climate of the SH circulation and their impacts on weather systems affecting WA in all seasons.
• Evaluate and use climate models to analyse projected future changes in the SH circulation and WA weather systems under different IPCC climate change senarios.
• Develop a methodology for attributing observed changes in the mean SH circulation using inverse modelling to identify a “fingerprint” of climate change forcing.

Figure 1.1.1: Shown in arbitrary units are the 300hPa streamfunction (left column) and the corresponding amplitude (right column) for the fastest growing Southern Hemisphere July storm track mode for 1949-68 (a, b) and 1975-94 (c, d). In the earlier period the major impact is over southwest WA; in the latter period it is in the central Pacific. The second fastest storm track mode for the latter period (not shown) has a similar structure to the fastest growing in the earlier period (a, b), but with a reduction of 33% in its growth rate.

References:
J.S. Frederiksen and C.S. Frederiksen, 2007: Inter-decadal Changes in Southern Hemisphere
Winter Storm Track Modes. Tellus, 59A, 599-617.
J.S. Frederiksen and C.S. Frederiksen, 2005: Decadal Changes in Southern Hemisphere Winter
Cyclogenesis . CSIRO Marine and Atmospheric Research Paper No. 002, 35pps.