我们知道,有潮港口的海面高度ζ(t)是周期性变化的。如果规定一个时间间隔τ,并在高潮前后分别找到两个时刻t_1和t_2,使τ=t_-t_1,以及ζ(t_1)=ζ(t_2)=Z_h,则海面高度Z_h被称为对应于时间间隔τ的高潮乘潮水位。类似地,在低潮前后满足t_2-t_1=τ以及ζ(t_1)=ζ(t_2)=Z_1的海面高度称为对应于时间间隔τ的低潮乘潮水位。由上述定义可知,在高潮前从某时刻开始,将有一段时间(τ),海面高度不低于Z_h;同样,在低潮前从某时刻开始,将有 We know that the sea level ζ (t) at the tidal harbor changes periodically. If a time interval τ is specified and two timings t_1 and t_2 are found before and after the climax so that τ = t_-t_1 and ζ (t_1) = ζ (t_2) = Z_h, the sea level Z_h is referred to as time corresponding to time Interval τ orgasm by the tide level. Similarly, the sea surface height that satisfies t_2-t_1 = τ and ζ (t_1) = ζ (t_2) = Z_1 before and after the low tide is called the low tide multiplied water level corresponding to the time interval τ. It can be seen from the above definition that there will be a period of time (τ) from a certain moment before the climax, and the height of the sea surface will not be lower than Z_h. Similarly, from a certain time before low tide, there will be