Simulation of barotropic wind-driven circulation in the upper layers of Bay of Bengal and Andaman Sea during the southwest and northeast monsoon seasons using observed winds |
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| Authors: | N Bahulayan A S Unnikrishnan |
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| Institution: | (1) Physical Oceanography Division, National Institute of Oceanography, 403 004 Dona Paula, Goa, India |
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| Abstract: | A two-dimensional, nonlinear, vertically integrated model was used to simulate depth-mean wind-driven circulation in the upper
Ekman layers of the Bay of Bengal and Andaman Sea. The model resolution was one third of a degree in the latitude and longitude
directions. Monthly mean wind stress components used to drive the model were obtained from the climatic monthly mean wind
data compiled by Hastenrath and Lamb. A steady-state solution was obtained after numerical integration of the model for 15
days. The sensitivity of the model to two types of open boundary conditions, namely, a radiation type and clamped type, was
tested. A comparison of simulated results for January with available ship drift data showed that the application of the latter
along the open boundary could reproduce all the observed features near the boundary and the interior of the model domain.
The model was integrated for 365 days to study the circulation during the southwest and northeast monsoon seasons. The model
was successful in simulating the broad features of circulation including gyres and eddies observed during both the seasons,
the development of north equatorial current during the northeast monsoon period and eastward moving monsoon drift current
up to 90°E during the southwest monsoon season. During the latter season, two anticyclonic gyres were observed in the central
and the southern parts of the Bay. A cyclonic type of circulation was prevalent in the central and western parts of the Bay
of Bengal during the northeast monsoon months of November and December. The simulated western boundary current along the east
coast of India, flows northward and southward during the southwest and northeast monsoon seasons respectively. It is presumed
that this western boundary current, simulated during both the seasons, is locally wind-driven. |
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| Keywords: | Barotropic circulation wind-driven layer seasonal variability Bay of Bengal numerical model boundary conditions steady-slate solution |
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