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The role of Arabian Sea in the evolution of Indian Ocean Dipole

Sayantani, O and Gnanaseelan, C and Chowdary, JS (2014) The role of Arabian Sea in the evolution of Indian Ocean Dipole. International Journal of Climatology, 34 (6). pp. 1845-1859.

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An Indian Ocean Dipole (IOD) event often evolves without any forcing from the Pacific. This study demonstrates that Arabian Sea spring warming and associated summer barrier layer (BL) play an important role in the evolution of such IODs. We propose an alternate mechanism for IOD initiation. Anomalous Walker circulation over the Indian Ocean during IOD years forced by Arabian Sea warming in spring and summer plays a crucial role in initiating the easterly wind anomalies in the eastern equatorial Indian Ocean. The western warming and the associated convection induce easterly wind anomalies much before the significant eastern cooling during IOD years, which strongly supports the role of western warming in the IOD evolution. IOD years are characterized by anomalous thickening of summer BL over the Arabian Sea. The anomalous BL formation during IOD years is attributed to the anomalous negative Ekman pumping velocity in the Arabian Sea. This negative Ekman pumping velocity forced downwelling deepens isothermal layer depth and thickens the BL. In addition to this, strong precipitation during IOD years strengthened the stratification and supported the BL formation. These favourable conditions for BL formation are absent during El Niño years. Anomalous BL is mainly responsible for the deepening of thermocline and subsurface warming in the Arabian Sea during IOD years

Item Type: Article
Additional Information: Copyright of this article belongs to Royal Meteorological Society.
Uncontrolled Keywords: Climatology; Earth atmosphere; Heat convection, Eastern equatorial Indian ocean; Ekman pumping; Indian Ocean dipole; Indian ocean dipoles; IOD; Subsurface warming; Walker circulation; Wind anomalies, Pumps, air-sea interaction; atmospheric convection; atmospheric transport; boundary layer; climate forcing; Ekman pumping; El Nino; spring (season); summer; Walker circulation; warming; wind direction; wind velocity, Arabian Sea; Indian Ocean; Indian Ocean (Equatorial)
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 28 Nov 2014 04:50
Last Modified: 28 Nov 2014 04:50

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