Tides and Tidal Current around Taiwan- Discussion

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Tides and Tidal Current around Taiwan- Discussion. Chang Hsien Kuo. 國立交通大學土木工程學系 中華民國 102 年 3 月 21 日. Variations of tidal range. Large tidal range at central western Taiwan.

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Tides and Tidal Current around Taiwan- Discussion

Chang HsienKuo

Variations of tidal range

Large tidal range at central western Taiwan

Fro:Current countermeasure of beach erosion control and its application in Taiwan-Ocean & Coastal Management, 53, Issue 9, September 2010, Pages 552–561

Variations of tidal range

Question:

Larger tidal range at central Taiwan strait and eastern Taiwan (HL) than those at KH and KL.

Bathymetric chart around Taiwan

Variations of tidal range

1. Inference– Interaction of two waves

Barotropic (propagating) tidal waves

Shoaling effect (shallow water):

Ks=(h1/h2)^(1/4)=(2000/80)^(1/4)

=(25)^0.25=2.25

Wave height at the Taiwan strait is about 2.25*0.8=2m

2. Standing Wave: 2*2=4m

Questions:

1. Where are anti-nodes of standing waves?

2. Why are larger tidal ranges at northern Taiwan than those at southern Taiwan

2. Inference– wave trapping over a ridge

• 臺灣西南及東北部海域滿潮時差皆大
• 臺灣中西部海域滿潮時差甚小
• 滿潮時差對臺灣海峽中段之對稱分布

• 實測及迴報(1996,3)

--基隆(KL)

• 竹圍(CW)
• 新竹(HC)
• 台中(TC)
• 澎湖(PH)
• 東石(TG)
• 高雄(KH)
• 成功(CK))

• 上海(7257-Zhenhai)
• 海門港(7236-Haimen Gang)
• 沙埕港(7224-Shacheng Gang)
• 三都澳(7219-Sando Ao)
• 馬祖(7216-Mazu Dao)
• 烏坵(7205-Wuqiu Yu)
• 料羅灣(7165-Liaoluo Wan)
• 汕頭港(7155-Shantou Gang)
• 臺灣環島沿岸
• 1995年平均潮差[年最大潮差]
• (劉文俊,1999)
• 基隆(KL) : 0.543 m [1.61 m]
• 淡水(TS) : 2.200 m [3.73 m]
• 竹圍(CW) : 2.539 m [4.11 m]
• 新竹(HC) : 3.495 m [5.15 m]
• 台中(TC) : 3.676 m [5.64 m]
• 箔子寮(PZ): 2.146 m [3.55 m]
• 東石(DG) : 1.459 m [2.53 m]
• 高雄(KH) : 0.492 m [1.38 m]
• 富崗(FK) : 0.962 m [2.06 m]
• 成功(CK) : 1.102 m [2.27 m]

龍洞

基隆

淡水

台中

澎湖

蘇澳

安平

高雄

恒春

基隆

蘇澳海脊

沖繩海槽

蘇澳

台中

恒春海脊

成功

蘭嶼海脊

台東海槽

蘭嶼

恒春

N

S

• 台灣海峽海域，位在一典型之陸架剖面地形上。
• 欲準確掌握台灣海峽海域內的潮波振盪特性，首先應充分含括東亞大陸棚架水深地形之總體效應(Lin et al., 2000)。
• 在考量陸架水深地形之影響下，Juang et al. (2001)及Jan et al. (2002)近斯內皆透過簡化的陸架地形，並以理論分析証明台灣海峽海域半日型主要分潮潮波的振盪型態係為部分重複駐波，但

• 只要陸架總長度滿足陸架上波動波長一半之整數倍，

3. Inference – partially standing waves

counterclockwise

4. Inference – Kelvin waves

Theory:Long wave considering Coriolis force

LeBlond, P. H. and <ysak, L. A. (1978) Waves in the ocean, Elsevir Scientific, p.211-214

4. Inference – Kelvin waves

(若以淺水波之反射理論見Mei (The applied dynamics of ocean surface waves, p. 119) r=[1-(h1/h2)^0.5]/ [1+(h1/h2)^0.5]計算因為海峽南端淺灘之波浪反射，假設淡水灘水深為80m，淺灘深為40m之條件來計算r只有0.17，因此若台中潮差遠大於台北潮差之2倍來看，只假設海峽潮汐特性因為海峽南端淺灘之波浪反射，似乎很難完全解釋。

Rotary tidal current

2009+2010

Taichung (TC)

Taipei (TP)

Rotary tidal current

2009+2010

KaoHsiung (KH)

Anpimg (AP)

Rotary tidal current

2009+2010

SuAo (SA)

HwaLien (HL)

Rotary tidal current

2009+2010

KeeLung (KL)