開放型沿岸域における流れに及ぼす風の効果  [in Japanese] Wind Effect on Currents in a Thin Surface Layer of Coastal Waters faced Open-Sea  [in Japanese]

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Abstract

沿岸域での風と流れの関係を調べるため,2年間に及ぶ風と流れの連続観測を実施した。観測海域は外洋に直接面した茨城県東海村沖である。沿岸水域特有の強い密度躍層の存在を考慮し,躍層以浅に注目した観測を行った。風と流れの変動は1日と数日以上の周期が卓越していた。風の長周期の変動には恒常的に北風成分が存在しており,これが沿岸部に南下流を作り出す一因となっている。また,風と0.5m深の流れの間には高い相関(2年間を通じての相関係数0.64)が得られた。1日周期の変動は,調和解析の結果,卓越するS_1分潮として現れたが,これは海陸風とそれによる吹送流であった。海陸風にはS_1以外の太陽潮周期の成分も含まれており,これは対応する分潮流に吹送流成分を加える。その結果,太陽潮周期の分潮流にはあたかも潮流のように振舞う吹送流(擬似潮流)が含まれる。Two-years of continuous observation of wind and current were carried out to investigate the relationship between them in the coastal waters off Tokaimura, Ibaraki prefecture. Three instruments to measure the current were set in a thin surface layer of 3m above the strong pycnocline, which is a common feature in coastal waters. Both of the power spectra of wind and currents showed very similar features, an outstanding high peak at 24-hour period and a range of high peaks longer than several-days period. The long term variation of the wind field always contained north-wind component, which contributed to forming the southward current along the shore throughout the year. A high correlation coefficient (0.64) was obtained between the wind and the current at a depth of 0.5m on the basis of the two-year observation. Harmonic analysis revealed that an outstanding current with 24-hour period was the S_1 component (meteorological tide), and was driven by land and sea breezes. These breezes also contained solar tidal components such as K_1, P_1 and S_2. These wind components added their own wind driven currents on the original tidal currents. This meant that land and sea breezes generated wind driven currents with solar tidal periods which behaved like astronomical tidal currents. As a result, coastal currents contained pseudo tidal currents which behaved like astronomical tidal currents.

Journal

  • Oceanography in Japan

    Oceanography in Japan 18(1), 37-55, 2009-01-05

    日本海洋学会

References:  17

Cited by:  1

Codes

  • NII Article ID (NAID)
    110007028667
  • NII NACSIS-CAT ID (NCID)
    AN10382760
  • Text Lang
    JPN
  • Article Type
    Journal Article
  • ISSN
    09168362
  • NDL Article ID
    9777026
  • NDL Source Classification
    ZM44(科学技術--地球科学--海洋・陸水・火山)
  • NDL Call No.
    Z15-778
  • Data Source
    CJP  CJPref  NDL  NII-ELS 
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