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Introducton to Indian Ocean Dipole
- 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