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Eda 20100924 Tide Gauge & AVISO. 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.
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Eda 20100924 Tide Gauge & AVISO
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
Comparison: Tide Gauge and AVISO 360d running mean & Low-pass
SST (color), SLP (contours) and wind stress (arrows) anomalies during +ve and –ve PDO’s +ve -ve
PDO-> Tide gauge Eddy-> Tide gauge PDO & eddy do not have direct correlation
Discussion Tide gauge : Kuroshio north east off Taiwan Tide gauges are locate at the special positions. They are not only affected by the wind, but also get the influence of eddy activity. From Qiu and Chen’s (2010) fig.3: Kuroshio is part of the gyre north of bifurcation point. This gyre is affected by the large scale wind (curl<0). When the gyre moves northward, the gradient of SSH becomes larger-> Kuroshio becomes stronger. This larger gradient is contributed by the eddy zone (see their fig. 3a) When the gyre moves southward, the “eddy zone” becomes wider, therefore, the eddy is not only affect “tide gauge”, but also south Taiwan and east Luzon. So, the eddy activity we defined in the “eddy zone” should also relates to the wind.
Tide gauge SSHA & area mean (2~20N,125~155E) wind stress curl
Tide gauge SSHA & area mean (2~20N,125~155E) wind stress curl anomaly
Discussion See Qiu and Chen’s fig.3 again… The Midanao current becomes stronger also when the Kuroshio strengthens. If Midanao current is affected the wind (curl>0, the region we are looking at): Curl increase -> Midanao current increase Midanao current increase -> Kuroshio also increase Therefore, we will get curl and tidegauge are correlated. Let’s see EOF will be more clearly….
(A) Philippine Sea WSCa_EOF1 (B) El Nino (C) TG WSCa_PC2 TG WSCa_PC1
Tide gauge & wind stress curl 5degx5deg …… Calculate the curl (i,j)=mean of 5degx5deg Remove the mean field of “2” Low-pass Do correlation • Tide gauge & wind stress curl 5degx5deg • …… • Calculate the curl • Remove the mean field • Low-pass • (i,j)=mean of 5degx5deg • Do correlation 1 2 Almost zeros everywhere…… Tide gauge & wind stress curl 5degx5deg …… Method 3: ??? 3