We investigated the vertical distribution of current velocity data of the entire water column at a site on the continental shelf of the northern South China Sea(SCS) from August 4 to September 6,2007,and found that th...We investigated the vertical distribution of current velocity data of the entire water column at a site on the continental shelf of the northern South China Sea(SCS) from August 4 to September 6,2007,and found that the characteristics of barotropic and baroclinic tides are mainly diurnal.During the observation period,we also estimated the mixing before and after the passage of Typhoon Pabuk.We found that the internal-wave-scale dissipation rate,the turbulent dissipation rate,and the mixing rate in every water layer increased by about an order of magnitude after the typhoon passage.We analyzed a case of abrupt strong current and calculated the mixing rate before,during,and after the typhoon event.The results show that the internal-wave-scale dissipation rate and the mixing rate in every water layer increased by about two orders of magnitude during the event,while the turbulent dissipation rate increased by about an order of magnitude.Passage of the abrupt strong current could also have increased the mixing rate of affected seawater by more than an order of magnitude.However,the passage of the typhoon differed in that there was an increase in mixing only in the lower layer where the abrupt strong current was particularly strong.The variation of the mixing rate may help us to understand the effects of typhoons and abrupt strong currents on the mixing of seawater.展开更多
Generally,tsunami waves become hazardous only when approaching the coast.Studying the runup and inundation of tsunami waves is important for understanding the tsunami evolution and for tsunami hazard assessment.Here,w...Generally,tsunami waves become hazardous only when approaching the coast.Studying the runup and inundation of tsunami waves is important for understanding the tsunami evolution and for tsunami hazard assessment.Here,we simulated the 1993 Hokkaido-Nansei-Oki(HNO) tsunami using a finite-difference model based on nonlinear shallow-water equations.We focused on the runup and inundation of tsunami wave propagation onto coastal area of Okushiri Island near Hokkaido,Japan,and investigate the relationship of different runup heights with the morphology and bathymetry of the seashore.In the simulation,a nested 4-layer grid system and moving boundary technique are adopted to study runup and inundation.The calculated tsunami heights and inundations in the region agreed well with field measurements.The local bathymetric and topographic characteristics had a first-order effect on the runup.Numerical experiments show that the focusing of certain local bathymetric features would amplify both wave height and current velocity remarkably.The results show that computation on dense grids is necessary to reproduce the observed runup heights,and inundation velocity is an important factor preventing tsunami devastation.In addition,we discussed the potential capability of sediment transport to illustrate the impact of tsunami waves on coastal geomorphology.展开更多
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KZCX1-YW-12-03)China National Funds for Distinguished Young Scientists, National High Technology Research and Development Program of China (863 Program) (Nos.2008AA09Z112,2008AA09A402)+1 种基金National Natural Science Foundation of China (No.40676021)the Chinese Oceanic Association (No.DYXM-115-02-4-02)
文摘We investigated the vertical distribution of current velocity data of the entire water column at a site on the continental shelf of the northern South China Sea(SCS) from August 4 to September 6,2007,and found that the characteristics of barotropic and baroclinic tides are mainly diurnal.During the observation period,we also estimated the mixing before and after the passage of Typhoon Pabuk.We found that the internal-wave-scale dissipation rate,the turbulent dissipation rate,and the mixing rate in every water layer increased by about an order of magnitude after the typhoon passage.We analyzed a case of abrupt strong current and calculated the mixing rate before,during,and after the typhoon event.The results show that the internal-wave-scale dissipation rate and the mixing rate in every water layer increased by about two orders of magnitude during the event,while the turbulent dissipation rate increased by about an order of magnitude.Passage of the abrupt strong current could also have increased the mixing rate of affected seawater by more than an order of magnitude.However,the passage of the typhoon differed in that there was an increase in mixing only in the lower layer where the abrupt strong current was particularly strong.The variation of the mixing rate may help us to understand the effects of typhoons and abrupt strong currents on the mixing of seawater.
基金Supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (No.KZCX1-YW-12-01)the National Natural Science Foundation of China (No.40576014)Science and Technology Planning Project of Guangdong Province,China (No.2005D33201006)
文摘Generally,tsunami waves become hazardous only when approaching the coast.Studying the runup and inundation of tsunami waves is important for understanding the tsunami evolution and for tsunami hazard assessment.Here,we simulated the 1993 Hokkaido-Nansei-Oki(HNO) tsunami using a finite-difference model based on nonlinear shallow-water equations.We focused on the runup and inundation of tsunami wave propagation onto coastal area of Okushiri Island near Hokkaido,Japan,and investigate the relationship of different runup heights with the morphology and bathymetry of the seashore.In the simulation,a nested 4-layer grid system and moving boundary technique are adopted to study runup and inundation.The calculated tsunami heights and inundations in the region agreed well with field measurements.The local bathymetric and topographic characteristics had a first-order effect on the runup.Numerical experiments show that the focusing of certain local bathymetric features would amplify both wave height and current velocity remarkably.The results show that computation on dense grids is necessary to reproduce the observed runup heights,and inundation velocity is an important factor preventing tsunami devastation.In addition,we discussed the potential capability of sediment transport to illustrate the impact of tsunami waves on coastal geomorphology.
