Tidal characteristics of the Bohai Sea and the Yellow Sea

      Tides in the ocean are tidal wave movements formed under the influence of tidal generating forces and the complex geographical environment on the earth's surface . For the ocean as a whole , It is a forced vibration . When ocean tidal wave propagation values offshore 、 Coastal time , The incident tidal wave encounters the obstruction of the continent and emits , And under the influence of the earth's rotation , Each sea area forms its own tidal wave system .

Tidal wave system is a complex movement , It can be expressed by the sum of many simple harmonic vibrations . A vibration is called a tidal component . Each tidal component can be imagined as caused by an imaginary celestial body moving in a circular motion on the celestial equator at a certain angular rate . Although there are many tides , But most of them have little impact , Generally selected 8-11 A larger tidal component , You can get a result with little deviation .

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this 11 A tidal component ,1~4 It's the semidiurnal tide ,5~8 It's the diurnal tide , The one with the largest amplitude 4 The three constituent tides are semidiurnal constituent tides M2、S2 And the diurnal tide K1 and O1.

There are 2 Control factors ： The amplitude H（ Half the tidal range ） And the late corner of the tide K（ The time interval between the celestial body and the high tide of the local tide ）,H and K Is the harmonic constant of the tidal component , They are decomposed from the actual tidal level observation data , This decomposition process is called tidal harmonic analysis .

The expression of tidal property adopts

Its ratio ：
0~0.5, It is a regular semidiurnal weekly tide , High and low tides twice a day are relatively regular ;
0.5~2.0 It is an irregular semidiurnal weekly tide , There are two irregular highs and lows every day ;
2.0~4.0 It is an irregular diurnal weekly tide , Part of the date is an irregular high and low tide ;
4.0 The above is the regular diurnal tide , Most dates are high and low tide .

The main content of the tide part of the hydrological report is to calculate this ratio based on the measured tide data , Get the nature of tides .

The largest tidal property ratio in China's sea area is wanjiatun, Qinhuangdao ：59cm/6cm=9.83; The area with the lowest ratio is Tuoji island in Penglai District, Qinhuangdao, Yantai ：0.11.

The tide of the Bohai Sea and the Yellow Sea is mainly caused by the semidiurnal tide , Sea areas with large tidal ranges belong to regular semidiurnal weekly tides , Places like wanjiatun, Qinhuangdao, where the semidiurnal tide is small and becomes a regular diurnal tide or irregular mixed tide area, also include the vicinity of the Yellow River Estuary 、 Shandong Gaojiao （ Northeast end of Shandong Peninsula ） And Subei District .

These four places are the semi diurnal tide free points in the Bohai and Yellow Seas , Both of them are the result of the reduction of the semi diurnal tide combined by the incident tide wave and the reflected tide wave due to their special geographical conditions .
The semi diurnal tide free point near Qinhuangdao is formed by the specific geographical conditions of Liaodong Bay and its adjacent areas ; The semi diurnal tide free point near the Yellow River estuary is formed by the specific geographical conditions of the Bohai Bay and its adjacent areas ; The tide free point of the semidiurnal tide outside Gaojiao, Shandong Province is formed by the specific geographical conditions of the West Korean Bay and the southern coast of Liaodong Peninsula ; The tide free point of semidiurnal tide in the North Jiangsu sea area is formed by the West Bank of Korea and the South Bank of Shandong Peninsula .
As the semi diurnal tide plays a role in the Bohai Sea area , Focusing on the formation and evolution of the tide free point of the semidiurnal constituent tide, we can find out the tidal distribution in the Bohai Sea . The picture below is M2 The tide is divided one day 0 Distribution map of predicted tidal height at .

When the crest of the tide is in the Bohai Strait , The trough of the tide is located in Bohai Bay and Liaodong Bay , Strait tide height 70cm, Liaodong Bay -120cm, Bohai Bay -70cm. Six hours later , When the trough of the tide is in the Bohai Strait , The crest of the tide moves to two bays , See the dotted line in the figure below . here , The height is the same as six hours ago, but the sign is opposite .

The law of tide in Bohai Sea is based on two tide free points 0 The line rises and falls periodically for the axis ,0 The tidal range on the line is small, but the tidal range of the two bays is large .

Some photos cannot be uploaded , Visible Male - many - Number .