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Revisiting the wintertime intraseasonal SST variability in the tropical south Indian Ocean: Impact of the ocean interannual variation

Li, Y and Han, W and Shinoda, T and Wang, C and Ravichandran, M and Wang, JW (2014) Revisiting the wintertime intraseasonal SST variability in the tropical south Indian Ocean: Impact of the ocean interannual variation. Journal of Physical Oceanography, 44 (7). pp. 1886-1907.

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Abstract

Intraseasonal sea surface temperature (SST) variability over the Seychelles-Chagos thermocline ridge (SCTR; 12°-4°S, 55°-85°E) induced by boreal wintertime Madden-Julian oscillations (MJOs) is investigated with a series of OGCM experiments forced by the best available atmospheric data. The impact of the ocean interannual variation (OIV), for example, the thermocline depth changes in the SCTR, is assessed. The results show that surface shortwave radiation (SWR), wind speed-controlled turbulent heat fluxes, and wind stress- driven ocean processes are all important in causing the MJO-related intraseasonal SST variability. The effect of the OIV is significant in the eastern part of the SCTR (70°-85°E), where the intraseasonal SSTs are strengthened by about 20 during the 2001-11 period. In the western part (55°-70°E), such effect is relatively small and not significant. The relative importance of the three dominant forcing factors is adjusted by theOIV, with increased (decreased) contribution fromwind stress (wind speed and SWR). The OIV also tends to intensify the year-to-year variability of the intraseasonal SST amplitude. In general, a stronger (weaker) SCTR favors larger (smaller) SST responses to the MJO forcing. Because of the nonlinearity of the upper-ocean thermal stratification, especially the mixed layer depth (MLD), the OIV imposes an asymmetric impact on the intraseasonal SSTs between the strong and weak SCTR conditions. In the eastern SCTR, both the heat flux forcing and entrainment are greatly amplified under the strong SCTR condition, but only slightly suppressed under the weak SCTR condition, leading to an overall strengthening effect by the OIV.

Item Type: Article
Additional Information: Copyright of this article belongs to American Meteorological Society.
Uncontrolled Keywords: Heat flux; Stream flow; Wind, Interannual variation; Intraseasonal SST variability; Madden-Julian oscillation; Sea surface temperature (SST); Short-wave radiation; South Indian Ocean; Strengthening effect; Turbulent heat fluxes, Oceanography, air-sea interaction; climate forcing; general circulation model; heat flux; Madden-Julian oscillation; sea surface temperature; seasonal variation; shortwave radiation; thermocline; winter, Indian Ocean; Indian Ocean (South)
Subjects: Oceanography > oceanography
Depositing User: INCOIS Library
Date Deposited: 08 Nov 2014 19:43
Last Modified: 08 Nov 2014 19:43
URI: http://moeseprints.incois.gov.in/id/eprint/851

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