Physical Mechanism behind the Occurrence of Aoshio in Omura Bay

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  • 大村湾における青潮発生の物理的なメカニズム
  • オオムラワン ニ オケル アオ チョウ ハッセイ ノ ブツリテキ ナ メカニズム

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Description

In order to understand the physical mechanism behind the occurrence of aoshio in Omura Bay, water mass movements by density currents under various wind conditions were simulated using a numerical model, COSMOS. This numerical model successfully reproduced physical structures such as temporal variations in water temperature in Omura Bay from spring through fall, 2008. In the transitional period from summer to fall, the bay-mouth water started to intrude into the bottom of Omura Bay and reached the innermost part of the bay after 11 days of the intrusion. In the simulation under no wind effect after the bottom intrusion of bay-mouth water, upward flows caused by density-induced circulation occurred in the innermost part of the bay. Furthermore, simulation under constant SE wind at a speed of3－4m s－1 after the start of bottom intrusion revealed that density currents in combination with moderate wind effects contribute to movement of the bottom water mass in the central bay to the surface of the innermost part of the bay. It is therefore concluded that the timing of the intrusion of bay−mouth water into the bottom of the central bay and wind conditions after the intrusion are both important for predicting the occurrence of aoshio in the innermost part of Omura Bay.

Journal

  • Bulletin on Coastal Oceanography

    Bulletin on Coastal Oceanography 53 (1), 65-72, 2015

    Coastal Oceanography Research Committee, the Oceanographic Society of Japan

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