Mean monthly wind driven climatological circulation model of the Bay of Bengal |
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Authors: | S K Dube Indu Jain A D Rao P C Sinha |
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Institution: | (1) Centre for Atmospheric Sciences, Indian Institute of Technology, Hauz Khas, 110016 New Delhi, India |
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Abstract: | A special feature of the Bay of Bengal circulation is its seasonal variation in response to the monsoonal winds. In the case
of the Bay of Bengal, observationally very little is known about the large scale circulation. Theoretically, the problem of
driving the circulation in the Bay of Bengal is more complex than that in other basins because of the presence of large quantities
of fresh water discharge from Ganga-Brahmaputra-Meghna river systems, and also because the atmospheric driving forces even
within a season are highly variable with frequent occurrences of tropical disturbances. Exploring the nature of the circulation
in the Bay of Bengal is a problem of great importance in itself as well as for the critical role this region plays in the
genesis of tropical disturbances which are the main source of large scale rainfall over the northern part of the Indian subcontinent.
The surface circulation of the Bay of Bengal may, therefore, help in understanding the variation of rainfall over time scales
ranging from the subseasonal to the interannual.
Keeping this in view, an attempt was made towards the development of an oceanic climatological circulation model for the Bay
of Bengal, which explains the seasonal variability of the currents. The model is fully non-linear and vertically integrated,
with realistic basin geometry. The treatment of coastal boundaries involves a procedure leading to a realistic curvilinear
representation of the western and eastern sides of the Bay of Bengal. This coastal representation has the advantage of taking
into account the finer resolution in the shallow regions of the northern Bay.
The model is forced by the monthly mean wind stress derived from 30 years (1950–79) of Comprehensive Oceanographic Atmospheric
Data Sets (COADS). Special emphasis is given to the southern open boundary condition for the model. For this purpose, sensitivity
experiments have been performed with six open boundary conditions and a comparative study of the results has been made. These
sensitivity tests for the open boundary condition will help the development of a suitable coupled ocean-atmosphere model for
this region. The model-generated main features are in general agreement with the known climatological circulation of the Bay
of Bengal. |
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Keywords: | Numerical model climatological circulation seasonal variability Bay of Bengal open-boundary condition |
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