Spatial extent and tidal characteristics of the diurnal tidal zone along the Yellow River Delta coast

Based on the observed tidal data along the Yellow River Delta coast in recent years, the spatial extent and tidal characteristics of the diurnal tidal zone are explored. The results demonstrate that the western boundary of the diurnal tidal zone along the north bank of the study area, lies between LaoJiuJin and 106 Gulf. The southern boundary, along the east bank, is in the southern part of the current Yellow River Estuary. It is deduced from the results of amphidromic points calculation and harmonic constant analysis that the amphidromic points of semi-diurnal constituents concentrating near the YRE generate the amphidromic region, which decrease the semi-diurnal constituents, and the diurnal constituents become the primary controls on overall tidal wave movement. From the combined analysis of theoretical calculation and observed data, the tidal characteristics of the diurnal tidal zone show that the spring and neap tides theoretically occur when the moon declination maximizes and minimizes, respectively. Periods of the diurnal tides make up two-thirds of the year, and periods of the semi-diurnal tides constitute the remainder. The tidal ranges are characterized by small tidal ranges and large differences between tidal ranges of the spring and neap tides. The flood tidal duration is longer than the ebb tidal one. The variations of sea level is greatly characterized by inter-monthly, inter-annual and intra-annual variations. The highest tidal level in summer half-years is higher than in winter half-years, and the lowest tidal level in winter half-years is lower than in summer half-years.