Acta Oceanol. Sin., 2014, Vol. 33, No. 1, P.35–41 DOI: 10.1007/s13131-014-0430-9 http://www.hyxb.org.cn E-mail: [email protected] A numerical study on the impact of tidal waves on the storm surge in the north of Liaodong Bay KONG Xiangpeng1∗ 1 Environmental Science and Engineering College, Dalian Maritime University, Dalian 116023, China Received 24 May 2013; accepted 20 October 2013 ©The Chinese Society of Oceanography and Springer-Verlag Berlin Heidelberg 2014 Abstract A storm surge is an abnormal sharp rise or fall in the seawater level produced by the strong wind and low pressure field of an approaching storm system. A storm tide is a water level rise or fall caused by the com- bined effect of the storm surge and an astronomical tide. The stormsurge depends on many factors, such as the tracks of typhoonmovement, the intensityof typhoon,the topographyof sea area, the amplitude of tidal wave, the period during which the storm surge couples with the tidal wave. When coupling with different parts of a tidal wave, the storm surges caused by a typhoon vary widely. The variation of the storm surges is studied. An once-in-a-century storm surge was caused by Typhoon 7203 at Huludao Port in the north of the Liaodong Bay from July 26th to 27th, 1972. The maximum storm surge is about 1.90 m. The wind field and pressure field used in numerical simulations in the research were derived from the historical data of the Typhoon 7203 from July 23rd to 28th, 1972. DHI Mike21 is used as the software tools. The whole Bohai Sea is defined as the computational domain. The numerical simulation models are forced with sea levels at water boundaries, that is the tide along the Bohai Straits from July 18th to 29th (2012). The tide wave and the stormtides caused by the wind field and pressure field mentioned above are calculated in the numerical simulations. The coupling processes of storm surges and tidal waves are simulated in the following way. The first simulation start date and time are 00:00 July 18th, 2012; the second simulation start date and time are 03:00 July 18th, 2012. There is a three-hour lag between the start date and time of the simulation and that of the former one, the last simulation start date and time are 00:00 July 25th, 2012. All the simulations havea same duration of5 days, which is same as the time length of typhoon data. With the first day and the second day simulation output, which is affected by the initial field, being ignored, only the 3rd to 5th day simulation results are used to study the rules of the storm surges in the north of the Liaodong Bay. In total, 57 cases are calculated and analyzed, including the coupling effects between the storm surge and a tidal wave during different tidal durations and on different tidal levels. Based on the results of the 57 numerical examples, the following conclusions are obtained: For the same location, the maximum storm surges are determined by the primary vibration (the storm tide keeps rising quickly) duration and tidal duration. If the primary vibration duration is a part of the flood tidal duration, the maximum storm surge is lower (1.01, 1.05 and 1.37 m at the Huludao Port,the DalingEstuaryand the Liaohe Estuary respectively). If the primary vibration duration is a part of the ebb tidal duration, the maximum storm surge is higher (1.92, 2.05 and 2.80 m at the Huludao Port, the Daling Estuary and the Liaohe Estuary respectively). In the mean time, the sea level restrains the growth of storm surges. The hour of the highest storm tide has a margin of error of plus or minus 80 min, comparing the high water hour of the astronomical tide, in the north of the Liaodong Bay. Key words: Liaodong Bay, tidal wave, storm surges, numerical study, typhoon Citation: Kong Xiangpeng. 2014. A numerical study on the impact of tidal waves on the storm surge in the north of Liaodong Bay. Acta Oceanologica Sinica, 33(1): 35–41, doi: 10.1007/s13131-014-0430-9 1 Introduction time as a high tide. Negative storm surge is a surge of water The main exploitation blocks of the Liaohe Oil Field are produced by an approaching storm that is below the normally in the Daling delta and Liaohe delta, where rivers flow into the expected water level - including the astronomical tides. It has north of the Liaodong Bay (Fig. 1). The tidal water often makes been matched negative storm tide. a strong impact on the production in these oil fields. Typhoon 9711 (Typhoon Winnie) landed at Panjin City on Stormsurgeis a abnormal sharp riseor fall in the seawater August 21st, 1997, as a tropical depression. Typhoon 7203 (Ty- level produced by the strong wind and low pressure field of an phoon Rita) landed at Tianjin City on July 27th, 1972 as a trop- approaching storm system. Storm surge is often confused with ical depression. The Storm surge caused by Typhoon 7203 is storm tide, which is a water level rise produced by the combined more remarkable than Typhoon 9711. In fact, the once-in-a- effect of the surge and the astronomical tide. Storm tide can century storm surge at the Huludao Port is caused by Typhoon produce severe flooding when storm surge occurs at the same 7203 (Jin, 1996). Therefore the Typhoon 7203 is a typical storm *Corresponding author, E-mail: [email protected] 1 36 KONG Xiangpeng et al. Acta Oceanol. Sin., 2014, Vol. 33, No. 1, P.35–41 Fig.1. The Sketch map of the water depth and the position of the Liaodong Bay. for studying the storm surge in the north of the Liaodong Bay. named as the Xiaoling River, the Daling River, the Liaohe River The storm surge is deviations of the astronomical tide and the Daliaohe River. There are four harbors in the north of from the storm tide (Flierl and Robinson, 1972; Johns et al., the Liaodong Bay (Fig. 1), namely, Bayuquan, Panjin, Jinzhou 1985; Wang and Chai, 1989; Zhou and Sun, 2000). and Huludao. The north of the Liaodong Bay is windy, and ty- The storm surge depends on many factors, such as the phoons and the storm surges are the disastrous factors in this track of a typhoon movement, the intensity of typhoon, the sea area. The floods and strong winds often lead to disasters in rainfall, the topography of sea area, the amplitude of tidal wave, summer. Anyway, the tide is the dominant hydrodynamic fac- the duration coupling with tidal waves. Therefore, there are tor in the sea area. difficulties in forecasting a storm surge and its characteristic- The diurnal constituent of tidal wave is a standing wave in s. The first fact is the prediction of arrival moment of the stor- the Liaodong Bay, the sea area from the north of the Liaodong m surge, which determines the coupling process-the high tide Bay to the latitude 40 degrees north gets a high tide (or low tide) contributes to the surge or the low tide detracts from the surge. at the same time. The semi-diurnal constituent of tidal wave The second fact is the determination of essential parameters, is a rotary tidal wave in the Liaodong Bay, being a synthesis of such as the wind velocity at landfall time, the water quantity standing wave and traveling wave, and the amphidromic point contributed by rainfall, the exact location of landfall, the effect is near to Qinhuangdao. Therefore, the north of the Liaodong on water movement from the topography. Bay is an irregular semi-diurnal tide sea area. The index is 0.58 Because the interaction between two long waves cannot at the Bayuquan Harbor, 0.54 at the Liaohe Estuary, 0.69 at the be neglected, the effect of storm surge coupling with a tidal Jinzhou Harbor, which is the ratio of the sum of the amplitude of wave during different tidal duration and on different tidal lev- tidal constituent K1 and O1 to the amplitude of tidal constituent el is studied in this paper. M 2. The TDD (theoretical depth datum) is 200 cm below the 2 Establishment of hydrodynamic model for the sea area Yellow Sea Datum at the Bayuquan Harbor, being 196 cm below the local mean sea surface. The TDD is 224 cm below the Yel- 2.1 Introduction of the general situation of research area low Sea Datum at the Liaohe Estuary, being 230 cm below the The research sea area in this paper, the north of the local mean sea surface. The TDD is 162 cm below the Yellow Liaodong Bay, locates north of the line between Bayuquan (at Sea Datum at the Jinzhou Harbor, being 162 cm below the lo- 40◦18’N; 122◦05’E) and Juhuadao (at 40◦29’N; 120◦50’E). There cal mean sea surface. It is obvious that the effect of topography are vast stretches tidal-flat areas and shallow water areas in this and shallow-water is important to the sea level in the north of sea area (Fig. 1). Four major rivers flow into the bay, respectively the Liaodong Bay (Jin et al., 1996). KONG Xiangpeng et al. Acta Oceanol. Sin., 2014, Vol. 33, No. 1, P.35–41 37 It is windy in the north of the Liaodong Bay. Typhoon and 2.4.2 Initial conditions and boundary conditions the storm surge as well as the heavy rainfall often cause a disas- Initial conditions are that both currents and surface ele- ter in this area.