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Water 2017, 9(10), 744; https://doi.org/10.3390/w9100744

Applying a Simple Analytical Solution to Modelling Wind-Driven Coastal Upwelling of Two-Layered Fluid at the Head of Tokyo Bay, Japan

1
College of Water Sciences, Beijing Normal University, Beijing 100875, China
2
Center for Spatial Information Science, The University of Tokyo, Kashiwa 277-8568, Japan
3
College of Life and Environmental Science, Minzu University of China, Beijing 100081, China
*
Authors to whom correspondence should be addressed.
Received: 4 August 2017 / Revised: 26 September 2017 / Accepted: 26 September 2017 / Published: 29 September 2017
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Abstract

Blue tides at the head of Tokyo Bay are a hydro-environmental phenomenon where seawater appears to be milky blue because of the reflection of the sunlight off surface water containing large amounts of sulphur particles. Its appearance is due to the coastal upwelling of bottom oxygen-depleted water induced by northeasterly wind-driven circulation. Blue tides cause the death of many shellfish and other aquatic animals across the head of Tokyo Bay and consequently result in substantial economic losses to coastal fisheries. This paper examines the occurrence of wind-driven blue tides in Tokyo Bay, based on a simplified hydrodynamic model and observational analysis. The model assumed a two-layer structure with a wind-driven upper layer and an oxygen-depleted lower layer. In this study, we derived a simple analytical solution to determine a critical wind condition for which the lower layer outcrops at the surface if the wind forcing is sufficiently strong, resulting in the mixing of the two layers and giving rise to blue tide. The results of sensitivity analyses of the analytical solution to all incorporated factors were found to be in accordance with a qualitative understanding of the blue tide phenomenon. More importantly, comparisons of observational data with real cases of blue tide during 1978–2016 and without blue tide during 2003–2016 suggested that this analytical solution was mostly valid. This study would be helpful for gaining a better understanding of the hydro-dynamical mechanism of blue tide. View Full-Text
Keywords: coastal upwelling; blue tide; Tokyo Bay; analytical solution; sensitivity analysis coastal upwelling; blue tide; Tokyo Bay; analytical solution; sensitivity analysis
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Zhu, Z.; Bai, X.; Dou, J.; Hei, P. Applying a Simple Analytical Solution to Modelling Wind-Driven Coastal Upwelling of Two-Layered Fluid at the Head of Tokyo Bay, Japan. Water 2017, 9, 744.

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