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Modulation of SST, SSS over northern Bay of Bengal on ISO time scale

Rao, SA and Saha, SK and Pokhrel, S and Sundar, D and Dhakate, AR and Mahapatra, S and Ali, S and Chaudhari, HS and Shreeram, P and Vasimalla, S and Srikanth, AS and Suresh, RRV (2011) Modulation of SST, SSS over northern Bay of Bengal on ISO time scale. Journal of Geophysical Research C: Oceans, 116 (9).

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Abstract

High resolution observations of atmospheric and oceanic variables are carried out at northern Bay of Bengal from 22nd July to 6th August 2009 on-board ORV Sagar kanya under the Continental Tropical Convergence Zone research/observational programme. Freshening of surface layer by more than 4 psu within 24 hours is observed, which is followed by warming in the surface layer temperature. The heat and salt budget analysis primarily indicates dominant role of advection processes on the evolution of temperature and salinity. The amount of rainfall received at observation site could not explain the observed freshening, thus an extensive analysis using wavelet coherence is done to find out the source of advected fresh water to the observed location. It is found that surface salinity in the northern Bay of Bengal (at 15 N) varies coherently with the rainfall over Ganga-Brahmaputra catchment area on intraseasonal time scale and with lag of about 60 days. Based on above observations, this study hypothesize that the intraseasonal rainfall variation modulates the amount of river discharge, which in turn modulates the salinity over northern Bay of Bengal on intraseasonal time scale. Since surface warming always follows the surface freshening, the time delay between the rainfall over catchment area and freshening at northern Bay of Bengal may explain the post monsoon warming. Importance of atmosphere-ocean coupling in driving the dynamics of the northern bay of Bengal has been clearly brought out in this study.

Item Type: Article
Additional Information: Copyright of this article belongs to American Geophysical Union.
Uncontrolled Keywords: Advection process; Atmosphere-ocean coupling; Bay of Bengal; Catchment area; Convergence zones; Fresh Water; High resolution observations; Intraseasonal time scale; Post-monsoon; Rainfall variation; River discharge; Surface freshening; Surface layer temperature; Surface layers; Surface salinities; Surface warming; Time-scales, Atmospheric thermodynamics; Catchments; Runoff; Salinity measurement; Time measurement, Rain, advection; atmosphere-ocean coupling; international organization; river discharge; sea surface salinity; sea surface temperature; timescale; wavelet analysis, Bay of Bengal; Brahmaputra Basin; Ganges Basin; Indian Ocean
Subjects: Meteorology and Climatology
Depositing User: IITM Library
Date Deposited: 11 Aug 2014 11:00
Last Modified: 11 Aug 2014 11:00
URI: http://moeseprints.incois.gov.in/id/eprint/681

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