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A dipole mode in the tropical Indian Ocean
N H Saji1, B N Goswami, P N Vinayachandran
1Institute for Global Change Research, SEAVANS N 7F, 1-2-1 Shibaura, Minato-ku, Tokyo 105 6791, Japan.
Nature
|July 25, 2006
Summary
Scientists discovered a new Indian Ocean Dipole mode, a unique air-sea interaction driving climate variability. This finding improves long-term rainfall anomaly forecasting for regions like East Africa and Indonesia.
Area of Science:
- Oceanography
- Climatology
- Meteorology
Background:
- Internal modes of climate variability are recognized in the Pacific and Atlantic oceans.
- A similar ocean-atmosphere interaction driving interannual climate variability was previously undiscovered in the Indian Ocean.
Purpose of the Study:
- To identify and characterize internal modes of climate variability in the Indian Ocean.
- To investigate the ocean-atmosphere interaction responsible for interannual climate variability in the region.
Main Methods:
- Analysis of observational data spanning the past 40 years.
- Examination of sea surface temperatures, wind patterns, and precipitation anomalies.
- Assessment of spatio-temporal links between sea surface temperatures and winds, considering ocean dynamics and precipitation.
Main Results:
- Discovery of the Indian Ocean Dipole (IOD) mode, a pattern of internal variability.
- The IOD exhibits anomalously low sea surface temperatures off Sumatra and high sea surface temperatures in the western Indian Ocean.
- This mode is coupled through precipitation and ocean dynamics, independent of the El Niño/Southern Oscillation, and explains 12% of Indian Ocean sea surface temperature variability.
Conclusions:
- The identified dipole mode is a unique, inherent air-sea interaction process in the Indian Ocean.
- Active IOD events correlate with severe rainfall in East Africa and droughts in Indonesia.
- The discovery enhances prospects for long-term rainfall anomaly forecasting in affected countries.
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