Nontidal sea level changes in Hiroshima Bay, Japan
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摘要: 本文研究了日本濑户内海广岛湾从亚潮周期(2天至1个月)到年际(大于2年)尺度的非潮汐水位变化。其水位变化的总标准偏差为12.5 cm。广岛湾水位年际变化的标准偏差为3.4 cm,年际变化率为4.9 mm/年。水位季节变化(8个月至2年)和季节内变化(1至8个月)的标准偏差分别为9.8 cm和4.7 cm。亚潮周期的水位变化明显,标准偏差为4.2 cm。本文特别研究了亚潮周期的水位变化。由于强北风的作用使得广岛湾(出口向南)北岸产生了上升流并随之发生了瞬间的水位变化,这一现象对亚潮水位的变化起到了非常显著的作用。瞬间的水位变化基本都超过10 cm,这是由于台风通过广岛湾东部400 km的纪伊半岛所引起的。利用研究区域内海陆边界上的压力平衡,验证了上述海平面变化的合理性。Abstract: Nontidal sea level changes generated in Hiroshima Bay of the Seto-Inland Sea in Japan are studied over various time scales, from the sub-tidal (2 d to 1 month) to inter-annual scales (>2 years). The total sea level variation produces a standard deviation (STD) of 12.5 cm. The inter-annual component of the sea level variation in Hiroshima Bay oscillates with a STD of 3.4 cm, forming a long-term trend of 4.9 mm/a. The STD of the sea level variation is 9.8 cm for the seasonal component (8 months to 2 years) and 4.7 cm for the intra-seasonal one (1 month to 8 months). Significant sea level variations with a STD of 4.2 cm also occur in the sub-tidal range. Special attention is paid to the sub-tidal sea level changes. It is found that the upwelling and associated transient sea level changes generated along the north coast of Hiroshima Bay (opened southward) by the strong northerly wind, play a significant role in sub-tidal sea level changes. The transient sea level changes are over 10 cm in most cases when caused by typhoons that pass through the Pacific Ocean off the Kii Peninsula, located at about 400 km east of Hiroshima Bay. Reasonable sea level changes are evaluated by the balance of pressure forces at the onshore and offshore boundary of the study domain.
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Key words:
- nontidal sea level changes /
- Hiroshima Bay /
- upwelling /
- transient sea level changes
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