Numerical Analysis of Storm Surge on the Radial Sand Ridges During “Muifa” Typhoon
The radial sand ridges (hereafter indicated as “RSRs”) in the South Yellow Sea are famous for its complex bathymetry and tidal wave systems. As marine development increasingly expanding, the characteristics of storm surge are crucial to the nearshore installations and navigation channels. Therefore, the evolution law of storm surge along with the changes of tide and wind is of great importance to protect the shoreline that is increasingly prone to flooding and erosion. Depending on the meteorological record from 1949 to 2007, 54% of typhoons moved northward in the East China Sea directly without landing. For the sake of investigating the spatial-temporal features of the storm surge, the same type of super typhoon as above ones named “Muifa” was selected and a coupled numerical model of WRF, and Mike-Flow was established with verification by observations of wind and flow velocity. Because the storm surge is susceptible with the typhoon intensity, and the extent of damage mainly induced by storm surge has a sharp rise in the highest and lowest astronomical tides at four times, namely T1, T2, T3, and T4 (T1 and T3 are the lowest tides, and others are the highest tides), were selected as the idealized tidal conditions to investigate the effects of tidal variations on storm surge during typhoon Muifa. The results showed that the weight of storm surge moved from the north to the south, but always near the 10 m isobath. The maximum of storm surge was 1.39 m when the Muifa came from the south at T1, but then fell to 1.28 m with the stronger wind at T2, the reason was the negative effect of the lower tide. The value jumped to 1.63 m with the stronger wind and the higher tide at T3. Finally, the value at T4 became only 0.6 m as the location of Muifa was too far to keep wind intensity. Although the wind intensity had a positive effect on the evolution of the storm surge, the macromareal tide made the storm surge decrease at the lowest tide with the stronger wind. The results of ten observation points showed that the peak value of the storm surge was high in the center of RSRs and low in northern and southern parts with the effects of bathymetry. Therefore, the wind, tide, and bathymetry are vital factors to calculate the storm surge and the central coastal area is susceptible to flooding induced by storm surge.
KeywordsTyphoon Muifa WRF Mike zero Storm surge Tidal various
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