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

As the original provider has changed how they update the index, we have decided to calculate it here using the HadISST1.1 SST dataset for the entire time period. Climatology is currently 1981-2010.

Time Interval: Monthly
Time Coverage: 1870 to present
Update Status: Periodically updated

Get Data:

New

DMI: Standard PSL Format (What is standard format?)
DMI: Western Indian Ocean PSL Format (What is standard format?)
DMI: Eastern Indian ocean Standard PSL Format (What is standard format?)

Source:
New Data is calculated at NOAA/PSL using the HadISST1.1 SST dataset. SST has 1981-2010 climatology removed for each month and the 2 regions are area averaged and subtracted from each other.

Source:
Old Data is from JAMSTEC via the page http://www.jamstec.go.jp/frcgc/research/d1/iod/e/iod/about_iod.html.
References:

1. Possible impacts of Indian Ocean Dipole mode events on global climate. Authors: Saji, NH;Yamagata, T, CLIMATE RES, 25 (2): 151-169 DEC 5 2003.

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