APSRU Seminar Series 19/05/05

Presenter:
Lexie Donald, Research Scientist, APSRU, DPI&F, Toowoomba

Topic:
"MJO research- where are we now?"

Abstract:
Over the past few years we have been conducting research into the relationship between the MJO and rainfall. This presentation includes the refinements and developments we have made to our MJO-rainfall discriminatory ability over the past year.

The MJO is a tropical phenomenon that travels East from its origin over the western Indian Ocean, and characterised by a region of active convection. The relationship between rainfall and MJO, and rainfall and MJO dependent on season has been established. Our results indicate that the MJO may be used as a forecasting tool. The equatorial passage of the MJO is associated with rainfall enhancement and suppression at higher latitudes.

Analysis of 30 years of daily rainfall data shows significant modulation of tropical and extra-tropical rainfall by the equatorial passage of the Madden Julian Oscillation (MJO). We used the Real-time multivariate MJO Index to determine the location and amplitude of the MJO from 1974 to 2004, and linked the passage of these MJO events with suppressed and enhanced global rainfall.

We also calculated the associated mean sea level pressure anomalies (MSLP) to determine synoptic scale features that might explain the observed rainfall anomalies. Thus, teleconnections responsible for the extratropical impacts of the MJO are suggested.

While not all the rainfall trends we see are caused by the MJO, the patterns are indicative of teleconnections, and the MJO is mechanistic in some. And adds to predictability. Given the previously-demonstrated predictability of the MJO, this opens the possibility to provide MJO-based, probabilistic forecasts. Discriminatory ability to predict near-global rainfall anomalies at intraseasonal time scales of one to eight weeks will bridge the weather / climate forecasting divide.
 

The PowerPoint Presentation of this seminar is available here as a pdf file (2.3MB).