Estimation of Wind Drift Current in the Soya Strait Wei Zhang, - - PowerPoint PPT Presentation

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Estimation of Wind Drift Current in the Soya Strait Wei Zhang, - - PowerPoint PPT Presentation

Dec 26, 2023 912 likes •1.26k views

Estimation of Wind Drift Current in the Soya Strait Wei Zhang, Naoto Ebuchi, Yasushi Fukamachi Institute of Low Temperature Science Hokkaido University zhangwei@lowtem.hokudai.ac.jp 1 The Soya Strait Russia Sea of Okhotsk China Japan

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Estimation of Wind Drift Current in the Soya Strait

Wei Zhang, Naoto Ebuchi, Yasushi Fukamachi

Institute of Low Temperature Science Hokkaido University zhangwei@lowtem.hokudai.ac.jp

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The Soya Strait

Connection of Sea

  • f Japan Sea and Sea
  • f Okhotsk

Soya warm current Fishery

Sea of Okhotsk

Japan Russia China

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Example of HF Radar Snapshot

17h20m (JST) 3 Aug 2003

http://wwwoc.lowtem.hokudai.ac.jp/hf-radar/index.html

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Interior Current Surface current

uwd: Wind Drift Current

Wind Drift Current

Wind

Cushuman-Roisin (1994)

i s wd

u u u

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Drift Parameter

Cushuman-Roisin (1994)

cos sin ( , ) sin cos A

α: speed factor θ: deflection angle W: wind vector

( , )

wd

u A W

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How to calculate wind drift parameter

Surface current (HF radar data) Interior current (ADCP data) Wind (JMA GPV/MSM)

min( ) ( ) ( , )

s err i

u A u u W

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Observation

  • HF radars
  • ADCP

(Bottom mounted)

  • Tide gauges
  • Wind

(JMA GPV/MSM)

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Example of ADCP vertical profiles

Monthly-mean of alongshore velocity observed by ADCP.

Fukamachi et al.(2010)

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Interior Current

Correlation Coefficient between sea level difference and alongshore velocities of different ADCP bins.

0.77 0.78 0.79 0.8 0.81 0.82 0.83 0.84 Correlation Coeffiicent 0.77 0.78 0.79 0.8 0.81 0.82 0.83 0.84 5 10 15 20 25 ADCP bins Number

Surface ~51m ~28m Bin10 Bottom

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10

Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08

  • 0.5

0.5 1 1.5 Alongshore Velocity (m/s) Alongshore Current HF Bin10 Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08

  • 0.1

0.1 0.2 height (m) Sea Level Difference Sea lever difference

Bin10 VS. Sea Level Difference

Alongshore velocities correspond well with sea level difference.

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Process Steps

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Monthly Drift Parameters

Root-Mean-Square error of monthly and daily drift parameters

Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08

  • 0.02
  • 0.01

0.01 0.02 0.03 0.04 time (month) speed factor speed factor Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08

  • 200
  • 150
  • 100
  • 50

50 100 150 200 250 time (month) deflection angle deflection angle

Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08 100 200 300 400 500 600 700 month number of data

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Average Drift Parameter

value RMSE Deflection angle 34 deg. 83 deg. Speed factor 0.0078 0.0156

Root-Mean-Square error of average and daily drift parameters

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Seasonal variation in drift parameters

Root-Mean-Square error of calendar monthly and daily drift parameters

1 2 3 4 5 6 7 8 9 10 11 12 200 400 600 800 1000 1200 1400 1600 calendar month number of data

2 4 6 8 10 12

  • 0.03
  • 0.02
  • 0.01

0.01 0.02 0.03 0.04 calendar month speed factor speed factor 2 4 6 8 10 12

  • 100
  • 50

50 100 150 200 250 deflection angle (deg.) calendar month deflection angle

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2 4 6 8 10 12 0.005 0.01 0.015 0.02 0.025 calendar month speed factor speed factor 2 4 6 8 10 12 10 20 30 40 50 60 70 80 90 100 deflection angle (deg.) calendar month deflection angle

Seasonal variation comparison

Seasonal variation in drift parameters are not significant.

Yoshikawa and Masuda (2009)

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Comparison1 for alongshore component

Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 time (month) RMS error (m/s) RMS of Alongshore Interior Current Monthly drift parameter Average drift parameter Seasonly drift parameter

High Error: Aug. Sept. Oct. Low Error: Dec. Jan. Feb. Mar. Apr. Correlation Coefficient

+: 90.35% +: 90.23% +: 90.34%

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Relationship between sea level difference and Bin10

  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 0.25 0.3 0.35

  • 1
  • 0.5

0.5 1 1.5 sea level difference (m) bin10 alongshore current (m/s) 2000 4000 6000 8000 10000 12000 14000 16000 18000

  • 1
  • 0.5

0.5 1 1.5 Time Serial (/hour) Alongshore Current (m/s) Estimated Current Alongshore Current

iSL

u a b

2.52 0.13 a b

Correlation coefficient: 81.26%

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Comparison2 for alongshore component

Correlation Coefficient

+: 74.69% +: 75.44% +: 71.77%

High Error: Aug. Sept. Oct.

Nov/06 Feb/07 Jun/07 Sep/07 Dec/07 Apr/08 Jul/08 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 time (month) RMS error (m/s) RMS of Alongshore Interior Current Driven from Sea Level Difference Monthly drift parameter Average drift parameter Seasonly drift parameter

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  • Oct. 07
  • Oct. 06
  • Aug. 07
  • Sept. 07

Wind in Summer

The wind is weak, and its direction is unstable.

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Wind in Winter

  • Dec. 07
  • Jan. 08
  • Feb. 08
  • Dec. 06
  • Jan. 07
  • Feb. 07

The wind is strong, and its direction is stable.

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Affection of bottom on drift parameter

* 2 1 4 1 *

0.4 40 10 , 1 10

E

U m f U ms f s

The bottom boundary layer affects on the wind drift current. The bottom boundary layer depth*:

Bottom boundary * Yoshikawa and Masuda (2009); Cushuman-Roisin (1994)

Surface Bottom ~51m ~28m 40m Bin10

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Affection of coastline on drift parameter

1/2 2 1

2 2.2 200 , 50

H H E H

A D km f A m s D m

The horizontal boundary layer effect on the wind drift current can be neglected. The horizontal boundary layer width*:

+ ADCP

* Yoshikawa and Masuda (2009); Pedlosky (1987)

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conclusion

Average drift parameter is a simple and effective way to estimate wind drift current. Wind drift current estimation is more accurate in winter and spring, but worse in summer and autumn. Seasonal variation in drift parameters are not significant. The bottom boundary layer affects wind drift current.

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Main reference

  • Yoshikawa, Y. and A. Masuda (2009): Seasonal variations in the

speed factor and deflection angle of the wind-driven surface flow in the Tsushima Strait. J. Geophys. Res. Oceans, 114, C12022, doi:10.1029/2009JC005632.

  • Cushuman-Roisin, B. (1994), Introduction to Geophysical Fluid

Dynamics, 320 pp., Prentice-Hall, Englewood Cliffs, N. J.

  • Fukamachi, Y., K. I. Ohshima, N. Ebuchi, T. Bando, K. Ono, and
  • M. Sano (2010): Volume Transport in the Soya Strait during 2006-

2008, Journal of Oceanography, 66, 685-696.

  • Pedlosky, J. (1987), Geophysical Fluid Dynamics, 2nd ed., 710 pp.,

Springer, New York.

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Thank you for your attention!!!

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Back up

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Back up

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2 4 6 8 10 12 0.005 0.01 0.015 0.02 speed factor speed factor 2 4 6 8 10 12

  • 100

100 200 deflection angle month deflection angle

Monthly drift parameter in seasonal variation

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Seasonal variation comparison

Seasonal variation in deflection angles are obvious.

2 4 6 8 10 12 0.005 0.01 0.015 0.02 0.025 calendar month speed factor speed factor 2 4 6 8 10 12 10 20 30 40 50 60 70 80 90 100 deflection angle (deg.) calendar month deflection angle

Yoshikawa and Masuda (2009)

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Wind direction in each month

  • Oct. 06
  • Nov. 06
  • Dec. 06
  • Jan. 07
  • Feb. 07
  • Mar. 07
  • Apr. 07

May 07

  • Jun. 07
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Wind direction in each month

  • Jul. 07
  • Aug. 07
  • Sept. 07
  • Oct. 07
  • Nov. 07
  • Dec. 07
  • Jan. 08
  • Feb. 08
  • Mar. 08
  • Oct. 07
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  • Apr. 08

May 08

  • Jun. 08
  • Jul. 08

Wind direction in each month