The Research Of Numerical Storm Surge Forecast Model In Jiangsu Coastal Areas

Storm surge is a phenomenon that the sea levels rise or decline anomaly, which is caused by the strong disturbance of atmosphere. The storm surge is one of the main Marine disasters in our country and it happens almost all over coastal areas of China. The typhoons landing in China and strong extratropical cyclone often result in storm surge disasters which are characterized by high frequency, great intensity and enormous economic losses. The storm surge disasters have been listed in hazard species in our country so far. Implementing risk assessments of Storm surge and accomplishing risk division can not only enhance the defense capability of disasters, but also effectively reduce the risk of storm surge disasters and the losses of life and property. Thus, they can provide a scientific basis for economic development layout of coastal areas. Therefore, it is quite meaningful of analyzing the storm surge stimulated by numerical model based on recording data.Storm surge prediction is very important in the ocean forecasting operation. There are two main methods of storm surge prediction, one is empirical statistical prediction and the other is numerical simulation prediction. The former mainly uses the regression analysis and statistical correlation to establish experience forecast equation or relevant charts between the wind and pressure measured by indicator stations and tide level measured by specific ports. This method has limitations and can only be applied to certain ports. But the latter one can overcome the weakness. So the fact is that forecaster usually combines the two methods in the forecast operation.The coastal of Jiangsu is the research area and this paper mainly studies the coasts of Nantong and Lianyungang. First, the ADCIRC ocean model covering East China Sea is built. The grids of Jiangsu coast are refined. Through the simulation of storm surge caused by historical typhoons and comparison with the recording data, we find that the results of stimulation approach to those of recording and the errors are allowable. It reveals that the ADCIRC model of storm surge can be applied to the research of surge in Jiangsu coastal areas.In order to study the effect of typhoon characteristic parameters on storm surge, we conduct a series of single variable sensitivity test. The typhoon center air pressure, maximum wind speed radius, the typhoon center moving speed and three typical typhoon paths(N1 represents the northward path close to Lvsi station, N2 represents the northward path away from Lvsi station, and NW represents the northwestward path) are selected in the sensitivity experiments. The study shows that the higher the central pressure of typhoon is, the larger the surge extremum is when other factors remain unchanged. There is rough linear correlation between central pressure and surge extremum. For N1, N2, NW typhoons, the surge rises about by 1.5838 m, 1.8824 m, 2.1037 m respectively, when the typhoon center pressure decreases average every 30 hPa. The greater the typhoon maximum wind speed radius is, the sooner the surge extremum appears when other factors remain unchanged. There is positive correlation between maximum wind speed radius and surge extremum. The surge extremum will rise larger as the maximum wind speed radius gets larger. However, the rising rate will get slow, if the maximum wind speed radius increases to a certain value. Then the surge extremum will not rise or even decline. For N1, the surge reaches maximum in case of the maximum wind speed radius increasing to 40 km, and the surge extremum declines when the maximum wind speed radius is over 40 km. The situation of N1 is also applied to that of N2 just replacing 40 km with 60 km. For NW, the surge extremum is rising along with the increasing of the maximum wind speed radius. But the surge extremum rising rate decreases significantly when the maximum wind speed radius equals to 80 km. The larger the wind speed is, the sooner the surge extremum appears, when others factors remain unchanged. But if the moving speed is too large, it does not contribute to storm surge. The effect of wind stress on seawater needs time to accumulate, and cannot be accomplished instantaneously. The larger the moving speed is, the shorter the time of impact on seawater is. Then the duration of surge process is shorter. From the surge curve of N2, we find that the greater the moving speed is, the smaller the surge extremum is, vice versa. Among the three typhoon paths, the surge and its extremum in NW path case is the greatest while those in N1 path case is the lowest. It shows that the path of NW is most conducive to surge of Jiangsu coastal areas.