Seasonal Variability in Circulation Pattern and Residence Time of Suo-Nada |
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Authors: | Rolando S Balotro Atsuhiko Isobe Manabu Shimizu |
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Institution: | (1) Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga, Fukuoka 816-8580, Japan;(2) Research Institute for Applied Mechanics, Kyushu University, Kasuga, Fukuoka 816-8580, Japan |
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Abstract: | The development and evolution of the persistent counterclockwise circulation in Suo-Nada have been studied in detail using
a three-dimensional numerical model. The realistic circulation has been reproduced from the monthly climatological fields
of salinity, temperature along the open boundary, wind, heat flux and buoyancy input from twenty-two major rivers surrounding
the basin. The seasonal variation of fresh-water discharge from the rivers proved to be the most important forcing mechanism
driving the circulation. The expansion and contraction of coastal low salinity water well corresponded with the development
of counterclockwise circulation from spring to summer and dissipation from autumn to winter. The circulation was found to
be vertically homogenous and quasi-barotropic. However, confined along the coastal zone is an estuarine flow (i.e., oppositely
directed currents in the upper and lower layers) whose horizontal dimension conforms to the period of maximum buoyancy flux
from the rivers. This indicates that the flow pattern in Suo-Nada can be separated into two distinct regions where the relative
dominance of estuarine circulation plays a significant role. Furthermore, the monthly water exchange capacity for autonomous
purification of the basin has been evaluated from the average residence time of conservative material based on the calculated
current field. It is demonstrated that the kinetic energy of the basin is directly responsible in promoting water exchange
in Suo-Nada.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | Counterclockwise circulation freshwater discharge heat flux coastal low salinity water density gradient kinetic energy seasonal estuarine index |
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