8. Conclusions

First, the generation and propagation of long ocean waves due to the atmospheric-pressure variation were simulated using the numerical model based on the nonlinear shallow water equations, where the atmospheric-pressure waves of four pressure-profile patterns traveled eastward over East China Sea, as well as the atmospheric-pressure waves that caused the large harbor oscillation in Urauchi Bay on February 25, 2009. The wave height of the long waves increased as the moving velocity of the pressure-recovery point was close to that of the long ocean waves. Before the oscillation attenuation in Urauchi Bay, the incidence of long waves can continue owing to an oscillation system generated between the main island of Kyushu and Okinawa Trough.

Second, the simple estimate equations were proposed to predict both the wave height and wavelength of severe meteotsunamis, using observed or GPV atmospheric-pressure data concerning the pressure profile of atmospheric-pressure waves or the recovery rate of atmospheric pressure in the ocean, without complicated calculation. The estimated values for both the wave height and wavelength of the long ocean waves showed good agreement with the corresponding computational data.

Third, numerical simulation was generated for the oscillation in the harbors of various shapes. The amplification factor at the head of the L-type harbor for the second mode increased, as its bending position was nearer to the harbor mouth. As Long-Wave Generation due to Atmospheric-Pressure Variation and Harbor Oscillation… DOI: http://dx.doi.org/10.5772/intechopen.85483

the narrowed area of the I-type harbor was located nearer to the harbor mouth, the amplification factor at the head for the first mode decreased, while that for the second mode increased. The C-type harbor showed the amplification depending on the position with the phase difference between the waves coming through two mouths. When the I-type harbor has the seabed crest, the amplification factor at the head for the first mode was larger than that for the second mode, while the reverse was true, when the I-type harbor has the seabed trough. Although the oscillation in Urauchi Bay had the second mode specific to T-type harbors, where antinodes appeared at their two harbor heads, future work is required to make clear the reason why the damping processes were different between Urauchi Bay and the T-type harbor.

Finally, the disaster measures were discussed against meteotsunamis, generated to propagate toward the west coasts of Kyushu. The methods of real-time prediction for meteotsunami generation were proposed using the inverse analysis, as well as the simple prediction equations, after which both the structural and the nonstructural measures against meteotsunamis were summarized.
