流速旋轉(zhuǎn)譜的定義：

旋轉(zhuǎn)譜計(jì)算方法（參考管守德博士畢業(yè)論文）

S_TIDE v1.23 update2 版本提供了s_rotation_spectra.m函數(shù)來(lái)計(jì)算旋轉(zhuǎn)譜，s_demo.m提供了旋轉(zhuǎn)譜的計(jì)算實(shí)例程序：

load tidalcurrents.mat

[Stv,Htv,Gtv,coef,xoutv,ju,Stint,Htint,Gtint,aa,bb,namev]=s_tide_m8(v,1,1,{'M2';'S2';'K1';'O1';'N2';'Q1';'P1';'K2'},8,1,'spline','robustfit',20.5,[2010,08,23,01,00,00],'corrected');

[Stu,Htu,Gtu,coef,xoutu,ju,Stint,Htint,Gtint,aa,bb,nameu]=s_tide_m8(u,1,1,{'M2';'S2';'K1';'O1';'N2';'Q1';'P1';'K2'},8,1,'spline','robustfit',20.5,[2010,08,23,01,00,00],'corrected');

% 20.5 is the latitude of the observation,[2010,08,23,01,00,00] is the start time of observation, users only need to change these two inputs when perform their own harmonic analysis.

% v and u are observed tidal currents at y and x axis

?%demonstration of s_rotation_spectra.m

?% this example was first added in S_TIDE v1.23 update2? ? 2022/01/05

[px,py,pcw,pccw,freq,rdn] = s_rotation_spectra(xoutu,xoutv,1/3600);

plot(24*3600*freq,log10(pcw),'r')

hold on

plot(24*3600*freq,log10(pccw),'k')

xlim([1.8 2.2]);xlabel('cycles per day(cpd)')

ylabel('PSD(m^{2}/s^{2}/Hz)')

line([24*0.080511 24*0.080511],[-5 5],'Linestyle','--');

text(1.94,-4,'M2');legend('clockwise','counterclockwise')

可以看到在M2頻率上順時(shí)針能量顯著大于逆時(shí)針，所以M2潮流是順時(shí)針旋轉(zhuǎn)的

[maxc,minc,maxt,mint,maxp,minp,rr]=s_estimate_tidal_ellipse(Htu(1,1),Gtu(1,1),Htv(1,1),Gtv(1,1),'M2')?

使用s_estimate_tidal_ellipse函數(shù)估算M2潮流橢圓旋轉(zhuǎn)率為負(fù)，同樣表明M2潮流是順時(shí)針旋轉(zhuǎn)