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Eda 20100903 Tide Gauge & AVISO. background. John et al. (2001) Tide gauge ∆SSHA Observed Kuroshio transport fv=g( d ƞ / dx ). Goal: Kuroshio variation east off Taiwan and its dynamics. Mean SSH from Rio et al.2009 Black dots are the locations of the tide gauge stations.

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Presentation Transcript
slide1

Eda

20100903

Tide Gauge

&

AVISO

background
background

John et al. (2001)

Tide gauge ∆SSHA

Observed Kuroshio transport

fv=g(dƞ/dx)

Goal:

Kuroshio variation east off Taiwan and its dynamics

slide3

Mean SSH from Rio et al.2009

Black dots are the locations of the tide gauge stations.

Blue contours are the isobaths.

Time period of data

Keelung: 1980-2009

Ishigaki: 1969-2008

Gangfeng: 1997-2007

Suao: 1999-2005

Lanyu:1992-2009

Dawu:2004-2009

data tide gauge
Data: tide gauge
  • Keelung & Ishigaki: (from university of Hawaii’s sea level web)

Hourly data

  • Ganfeng, Suao, Dawu and Lanyu: (from cwb)

High tide and low tide (about every 6 hour)

All data had done 40hr low pass first

Then, save into daily format

slide6

The linear regression is done in order to fill in the gap.

1.Ganfeng and Keelung (same side)

Fill in the gap of Keelung.

2.Keelung and Ishigaki

Fill in the gap of Ishigaki

Ganfeng & Keelung

Keelung & Ishigaki

slide7

Anomaly of Ishigaki-Keelung

Black: monthly mean

Red: 360days running mean

nino3 4 west pacific with tide gauge ssha
Nino3.4, West Pacific with Tide Gauge SSHA

Colored bar are Nino3.4 or WP

Contour is tide gauge SSHA

SSHA does not correlate with Nino3.4.

The correlation is better in WP (yellow box)

aviso tide gauge
AVISO & Tide Gauge
  • Time: 1992/10/14~2008/12/31 (16 years)
  • Tide Gauge : Ishigaki, Keelung
  • AVISO: SSH, Ug, Vg (1/5 degree)
  • Both tide gauge and AVISO data are monthly averaged

Discussion:

What contribute to the variation of the Kuroshio northeast off Taiwan?

In order to answer this, the next part is the regression (correlation) between Tide Gauge SSHA and AVISO SSH, Ug, Vg.

slide10

Regression

Y(i,j)=a(i,j)+b(I,j)*X

X:tide gauge, Y:AVISO

Plotted here is b

Correlation coefficient

Correlation Coef. Is very similar to regression b. The following plot will only use “b”.

Tide gauge SSHA correlates well with a zonal band region east of Taiwan.

zonal band high eke region
Zonal band=high EKE region

The eddy activity contributes to the variation of Kuroshio transport northeast off Taiwan.

slide12

Regression, Vg

Regression, Ug

Tide Gauge SSHA has good correlation with Kuroshio upstream and the Mindanao Current

Eddy zone (anti-cyclonic eddy)

Two branches of Kuroshio; East China Sea; Ryukyu Island

p.s. the regressions are very similar to dSSH/dx, dSSH/dy (fig. not shown).

slide13

corr

Defined eddy zone

Tide Gauge SSH (black) &

mean eddy zone SSHA (red)

Eddy activity has important influence to the variation of Kuroshio transport east off Taiwan

slide14

Regression : AVISO ∆SSH (same locations) & AVISO

Regression : AVISO ∆SSH (East Luzon) & AVISO

High regression also shows in eddy zone.

Further south, at east of Luzon, the Kuroshio transport does not have high regression with eddy zone

slide15

East Luzon AVISO ∆SSH & AVISO Vg

Interestingly, the Kuroshio transport east off Luzon does not correlate well with futhur north transport.

summary
summary
  • Kuroshio transport east off Taiwan is affected by eddy activity, therefore, it shows different variation with East Luzon transport where is south of the eddy zone.
  • Tide gauge ∆SSH has good regression with two branches of Kuroshio; one enter East China Sea; the other one moves along Ryukyu Island