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Anomalous intraseasonal events in the thermocline ridge region of Southern Tropical Indian Ocean and their regional impacts

Jayakumar, A and Gnanaseelan, C (2012) Anomalous intraseasonal events in the thermocline ridge region of Southern Tropical Indian Ocean and their regional impacts. Journal of Geophysical Research C: Oceans, 117 (3).

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Abstract

The present study explores the mechanisms responsible for the strong intraseasonal cooling events in the Thermocline Ridge region of the southwestern Indian Ocean. Air sea interface and oceanic processes associated with Madden Julian Oscillation are studied using an Ocean General Circulation Model and satellite observations. Sensitivity experiments are designed to understand the ocean response to intraseasonal forcing with a special emphasis on 2002 cooling events, which recorded the strongest intraseasonal perturbations during the last well-observed decade. This event is characterized by anomalous Walker circulation over the tropical Indian Ocean and persistent intraseasonal heat flux anomaly for a longer duration than is typical for similar events (but without any favorable preconditioning of ocean basic state at the interannual timescale). The model heat budget analysis during 1996 to 2007 revealed an in-phase relationship between atmospheric fluxes associated with Madden Julian Oscillation and the subsurface oceanic processes during the intense cooling events of 2002. The strong convection, reduced shortwave radiation and increased evaporation have contributed to the upper ocean heat loss in addition to the slower propagation of active phase of convection, which supported the integration of longer duration of forcing. The sensitivity experiments revealed that dynamic response of ocean through entrainment at the intraseasonal timescale primarily controls the biological response during the event, with oceanic interannual variability playing a secondary role. This study further speculates the role of oceanic intraseasonal variability in the 2002 droughts over Indian subcontinent.

Item Type: Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Uncontrolled Keywords: Air-sea interface; Atmospheric fluxes; Biological response; Heat budget analysis; In-phase; Indian ocean; Interannual; Interannual variability; Intraseasonal variability; Madden-Julian oscillation; Ocean general circulation models; Ocean response; Regional impacts; Satellite observations; Short-wave radiation; Strong convections; Time-scales; Tropical Indian ocean; Upper ocean; Walker circulation, Climate change; Cooling; Dynamic response; Experiments; Heat flux; Stream flow, Oceanography, air-sea interaction; annual variation; cooling; evaporation; heat budget; heat flux; Madden-Julian oscillation; oceanic general circulation model; satellite data; seasonality; shortwave radiation; thermocline; timescale; tropical region; Walker circulation, Indian Ocean; Indian Ocean (Southwest); Indian Ocean (Tropical)
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 22 Dec 2013 05:58
Last Modified: 22 Dec 2013 05:58
URI: http://moeseprints.incois.gov.in/id/eprint/516

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