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Indian Ocean Dipole (IOD) by the LAS

Lively Data: December 22, 2008

Maps of Merged Sea Level Anomalies (SLA) in cm and averaged over fall months (September-November) for year 2006. A white line represents the area for the hovmoeller diagram below. Choose Near-real time Data, Global, (Maps of) Sea Level Anomalies, merged. Define the period in Define variable and select "T" in Apply to these axes and "Average" in Select analysis type. Then select the geographical area and a color fill levels (-35)(-30,30,0.5)(35).

The Indian Ocean Dipole (IOD) is an air-sea coupled climate mode in the Indian Ocean with some positive and negative events. It has large climate impacts: floods in East Africa and droughts in Indonesia and parts of Australia and Indian summer monsoon rainfall remains above normal during a positive IOD. IOD generally starts to develop in boreal summer, peaks in fall and terminates in winter, subject to the strong seasonal surface winds.

Three consecutive positive IOD events have occurred in 2006, 2007 and 2008. No such previous occurrences had already been recorded.

Maps made with the LAS can easily draw the spatio-temporal evolution of this phenomena. with the longitude-time hofmoeller diagram (xt). A first map on averaged Sea Level Anomalies during the strong positive IOD in 2006 boreal fall (Sept. Oct. Nov.), clearly show the signature of this event : a negative SLA along the west coasts of Sumatra and positive SLA in the western Indian Ocean.

A longitude-time diagram (also called Hovmoeller, xt) also show these positive anomalies that move towards west, the strong event in 2006 and the three consecutive events since this date.

Longitude-time diagram of merged Sea Level Anomalies in cm, between 54 °E and 106°E, for the latitude 10°S (located by the white line above) between 2002 and November 2008. Choose Near-real time Data, Global, (Maps of) Sea Level Anomalies Merged, the kind of diagram in Select view (longitude-time hofmoeller (xt), the latitude (10°S) and West/East borders.

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