Improved schemes of quasi-harmonic method for tide prediction of shallow water ports

Two improved schemes(Ⅰand Ⅱ) of quasi-harmonic method for tide prediction of shallow water ports are proposed.SchemeⅠadds 14 circles perday,16 circles perdya and 6 quasi-harmonic terms which are related to previous tide status based on Fang Guohong(2001).SchemeⅡis the method proposed by Wang Ji in 2001 and adopts another 5 quasi-harmonic terms based on the SchemeⅠ.Both of them adopt the same 57 harmonic constituents.However,how to group the constituents and what kind of quasi-harmonic terms are derived from the constituents are different.It takes 40 quasi-harmonic terms to denote the shallow water effect in the SchemeⅠ.The 18 terms of long period,diurnal and semidiurnal quasi-armonic terms are included in the SchemeⅡ.The results show that the precision of both SchemeⅠand SchemeⅡ is obviously improved compared with Fang Guohong(2001) and traditional standard harmonic analysis method.For the first type shallow water ports,such as Wusong Station,all 8 prediction indexes are obviously improved.Especially the roo-tmean-square of low water time is reduced from 26.8 to 15.1 min.For the second type shallow water ports,such as Chensanjiao Station,the root-mean-square of high water time is reduced remarkably from 39.6 to 26.7 min.