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

Two improved schemes(ⅠandⅡ) of quasi-harmonic method for tide prediction of shallow water ports are proposed.SchemeⅠadds 14 circles per day,16 circles per dya and 6 quasi-harmonic terms which are related to previous tide status based on Fang Guohong(2001).Scheme Ⅱis 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-harmonic terms are included in the Scheme Ⅱ.The results show that the precision of both Scheme!Ⅰand Scheme Ⅱ 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 root-mean-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.