半閉鎖性海域湾口部における成層期および成層崩壊期の流動構造と海水交換について  [in Japanese] UPPER-OCEAN DYNAMICS AND WATER-EXCHANGE AT THE ENTRANCE OF A SEMI-ENCLOSE BAY UNDER STRATIFIED AND UNSTRATIFIED CONDITIONS  [in Japanese]

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Abstract

半閉鎖性内湾である和歌山県田辺湾湾口部において,ADCP,塩分水温計などを用いた長期連続観測を行い,主に流動構造と海水交換特性に関する解析を行った.クロススペクトル解析結果から,流速鉛直構造と外力との対応については,表層付近の日周期変動には海上風が,成層期の混合層下部の半日周期変動には内部潮汐が,成層崩壊期の混合層全層では半日周期潮汐がそれぞれ寄与していることが分かった.一方,海水交換に対しては半日周期潮汐変動が最も寄与しているのに対し,それと同程度に周期約3日にピークを有するサブタイダル長周期成分の影響が大きかった.この長周期変動は紀伊水道スケールで生じる地形性のメソスケール渦の消長と密接に関係しており,モデルによる先行研究と整合的であった.

 For rigorious description of upper ocean dynamics and resultant volume transport at the mouth of Tanabe Bay, Wakayama, Japan, a comprehensive field campaign was conducted from summer to fall of 2015. The vertical structure of transient dynamics in the surface boundary layer and consequent water exchange at the mouth are characterized by high-frequency variability peaked at around the semi-diurnal period as well as in the lower-frequency subtidal band centered at 3 day period, consistent with the previous modeling study. A spectral coherence analysis indicates that near-surface currents are mainly driven by wind stress peaked at the diurnal frequency, whereas subsurface currents fluctuate rather by semi-diurnal internal tides. The upper ocean cools down gradually, corresponding to seasonal transition from summer to fall condition. However, an abrupt cooling event is observed albeit in a calm local forcing condition where an offshore subtidal cold water intrusion induced remotely by the fluctuating Kuroshio path plays an essential role.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal Engineering) 72(2), I_493-I_498, 2016

    Japan Society of Civil Engineers

Codes

  • NII Article ID (NAID)
    130005282327
  • Text Lang
    JPN
  • ISSN
    1884-2399
  • NDL Article ID
    027809011
  • NDL Call No.
    YH267-236
  • Data Source
    NDL  J-STAGE 
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