Primary introduction to indian ocean dipole and it's impact

1. INDIAN OCEAN DIPOLE
By
Shubham Raghuwanshi

2. • Introduction to Indian Ocean
• What is Indian ocean dipole ?
• Evolution of Dipole
• Impacts of IOD

3. • Third largest of the world's oceanic divisions
• Covering 20% of water on earth surface
• Located between 30E -120E and 30N -60S
•The climate north of the equator is affected by
a monsoon climate

4. • Wind blow from south west during (may-sep) and north-east
during Nov-feb
• Warm water(SST) on eastern side and cooler on west
• More fresh water input on eastern side than west
• Upwelling system is located off the west
• Deeper thermocline in the east than west
• Convection is higher over eastern part and lesser over west
• Wyrtki jets (over equatorial Indian ocean) transport warmer
upper layer water towards the east during April-may and oct-
nov.
• Heat content is larger on eastern side than west
• Lower salinity on east than west

5. Source: CSIR – National Institute of Oceanography

6. • The departure of ocean–atmosphere system from this
mean state occurring during certain years,
characterized by opposite sign of anomalies in the
east and west is known as the Indian Ocean dipole

7. • The Indian Ocean Dipole is defined by the difference
in sea surface temperature between two areas (or
poles, hence a dipole) a western pole in the Arabian
Sea (western Indian Ocean) and an eastern pole in the
eastern Indian Ocean south of Indonesia.
• The IOD affects the climate of Australia and other
countries that surround the Indian Ocean Basin, and
is a significant contributor to rainfall variability in
this region.

8. DMI=SSTA West -SSTA East
West = 50°E-70°E;10°S-10°N
East = 90°E-110°E;10° S-0°

9. Source: http://www.enviroinfo.com.au/understanding-the-indian-ocean-dipole
phenomenon/#.U3SfH4GSxVM

10. Source: Bureau of Meteorology Australia

11. • It’s a coupled ocean-atmosphere processes
• Oceanic processes
– Shoaling of thermocline
– Variations in mixed layer depth
• Atmospheric process
– Atmosphere-ocean heat fluxes
– Large-scale atmospheric circulations

12. • During 1957-1999 about 50% of IOD events have
occurred together with ENSO and the rest
independently
• Some coupled model found relation between ENSO
and IOD but others doesn’t

13. • Affects the rainfall in tropical eastern Africa,
Indonesia, Australia
• It’s found positive IOD event Intensify ISMR
(Ashok et al 2001, guan et al 2003)
• Enhanced the impact of Enso on Australia

14. • Indian Ocean Dipole :Dominant signal in the inter-
annual variability.
• Coupled ocean – atmospheric phenomenon in the
Indian Ocean. SST, thermocline, winds convection all
take part in an IOD event.
• OGCMs reproduce IOD events well and illustrate the
role of ocean dynamics in the evolution of SST
anomalies.
• Unresolved issues: Triggering, dependence on ENSO,
intraseasonal oscillations, impact on monsoons.

15. • Noaa http://www.noaa.gov/
• Bureau of Meteorology Australia
http://www.bom.gov.au/climate/IOD/about_IOD.shtml
• Japan agency for marine earth science and technology
http://www.jamstec.go.jp/e/
• Vinaychandran P N, Francis P A and Rao S A 2009 Indian ocean
Dipole: Processes and Impacts
• Wang Xin & Wang Chunzai 2013 Different impacts of various El
Nino events on Indian ocean dipole

16. Thank You