Seasonal Prediction

What is IOD?

Indian Ocean Dipole (IOD) is a coupled ocean-atmosphere phenomenon in the Indian Ocean. It is characterized by anomalous cooling of SST in the south eastern equatorial Indian Ocean and anomalous warming of SST in the western equatorial Indian Ocean. Associated with these changes the normal convection situated over the eastern Indian Ocean warm pool shifts to the west and brings heavy rainfall over the east African and severe droughts/forest fires over the Indonesian region.

Who discovered/named the IOD?

The IOD was first identified by Prof. Yamagata, Dr. Saji and other researchers of the Climate Variations Program of Frontier Research System for Global Change. The name IOD is coined by this group to represent the dipole structure of the various coupled ocean-atmosphere parameters such as SST, OLR and Sea Surface Height anomalies.

How does one represents the IOD?

Intensity of the IOD is represented by anomalous SST gradient between the western equatorial Indian Ocean (50oE-70oE and 10oS-10oN) and the south eastern equatorial Indian Ocean (90oE-110oE and 10oS-0oN). This gradient is named as Dipole Mode Index (DMI). When the DMI is positive then, the phenomena is refereed as the positive IOD and when it is negative, it is refereed as negative IOD.

Is there any connection between the ENSO and the IOD?

It is shown by several researchers that the IOD in the Indian Ocean can evolve without the ENSO forcing from the tropical Pacific. However, some researchers argue that in some occasions ENSO can force the IOD. This complex relation between the ENSO and the IOD needs further confirmation.

Does the IOD has any influence on other climate signals?

Yes, IOD significantly influences various climate signals. For example, Indian Mosoon rainfall, Japan Summer air temperatures, Australian rainfall and the SOI to name a few.