Yu-Lin Eda Chang National Taiwan Normal University Critical
wind condition and current reversals in the Taiwan Strait
Co-author: L.-Y. Oey, Y.-C. Lin, M.-C. Chang, and S. Varlamov
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2012/03/15 2012/04/01 Shipwreck incident near Xiamen Debris
were found at Tauyuan 50 200 Mean Transport : 1.8 Sv Winter:0.9 Sv
[Wang et al, 2003] Winter: 0.12Sv [Lin et al, 2005] Why and how
could the cross-strait flow occur during northeasterly monsoon
?
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Tracer simulation with/without Stoke drift No wave With wave
Difference
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Analytical model: Follow the quasi-steady, depth average: rv A
= -g / y + oy /H r ~ 1.610 -5 (s -1 ) / y ~ -4.510 -7 u o = -(g/f).
/ y + oy /(f E ) v o = -(g/r). / y + oy /(f E ).[1 + f E /(Hr)]
Critical Along-Strait Wind v o =0, v oy ~ -1.210 -4 (m 2 s -2 ) [~
-10m/s] u o =0, u oy ~ -0.6810 -4 (m 2 s -2 ) [~ -7m/s]
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EOF analysis : mode 1 Corr( oy (v o ), PC)=0.83Corr( oy (v o ),
PC)=0.93 v o = -(g/r). / y + oy /(f E ).[1 + f E /(Hr)]
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u ~ u PG + u wind + u PG v o = -(g/r). / y + oy /(f E ).[1 + f
E /(Hr)] v m ~ v o + v oPG Corr(PC uv, Vo PG )=0.61 Corr(PC , Vo PG
)=0.70 Corr( oy, PC)= 0.68Corr( oy, PC)= 0.52 EOF analysis : mode
2
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Summary Flow tends to be southwestward if the Northeasterly
wind stress is stronger than |1.210 -4 | m 2 s -2 Flow tends to be
northeastward if the Northeasterly wind stress is weaker than
|0.6810 -4 | m 2 s -2 The model tracer-tracking simulations support
such a scenario, and it demonstrates the importance of wave-induced
Stokes drift in advecting the debris to the near-coast regions The
first two modes of EOF account for 70~85% total variance. The first
mode explains the quasi-steady pressure gradient and wind forced
velocity. The second mode is affected by the fluctuating pressure
gradient
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ATOP - Advanced Taiwan Ocean Prediction System Resolution: 0.1
x0.1 deg x 41 sigma levels Free Running from 1987 to 2011 Forecast:
2012/Jan-present NCEP-GFS wind, -7days hincast~7days forecast (No
data assimilation on the shelf) Oey, et al, 2012