Wave fields in Beibu Bay during Typhoon Damrey （2005） were simulated by SWAN wave model through inputting high resolution reanalysis wind fields data, current and water level data. Comparisons for wind input and wav...Wave fields in Beibu Bay during Typhoon Damrey （2005） were simulated by SWAN wave model through inputting high resolution reanalysis wind fields data, current and water level data. Comparisons for wind input and wave hindcast between observation and simulation show good consistency. Distributions of wave parameters such as wave height, wave period, wave length and wave direction under typhoon wind forcing were given. Also, the directional spectra related to the different position from the typhoon center were discussed. And at last, the variation and characteristics of observed frequency spectrum during the passage of Damrey were presented.展开更多
The strong wind characteristics of the Runyang Suspension Bridge（ RSB） including the wind speed and direction, the turbulence intensity, the turbulence integral length and power spectrum are analyzed based on measur...The strong wind characteristics of the Runyang Suspension Bridge（ RSB） including the wind speed and direction, the turbulence intensity, the turbulence integral length and power spectrum are analyzed based on measurement data from the wind environment monitoring subsystem of the structural health monitoring system （SHMS）of the RSB and field tests during strong winds. The differences between the typhoon and the strong northern wind are especially studied. It is found that the mean wind speed of the strong northern wind is a little smaller and the mean wind direction is more stable than that of the typhoon. The turbulence intensity of both the typhoon and the strong northern wind is greater than the values suggested in Chinese code, and the turbulence integral length difference between the typhoon and a strong northern wind is not clear. As for the along-wind turbulence power spectrum, the spectrum of the strong northern wind can fit the Kaimal spectrum better than that of the typhoon. The obtained results can provide measurement data for founding a strong wind characteristic database and determining the strong wind characteristic parameter values of the RSB.展开更多
In order to facilitate engineering design and coastal flooding protection, the potential storm surge induced by a typhoon is studied.Using an unstructured mesh, a coupled model which combines the advanced circulation ...In order to facilitate engineering design and coastal flooding protection, the potential storm surge induced by a typhoon is studied.Using an unstructured mesh, a coupled model which combines the advanced circulation （ ADCIRC ） hydrodynamic model and simulating waves nearshore （ SWAN ） model is applied to analyze the storm surge and waves on the coast of Jiangsu Province.The verifications of wind velocity, tidal levels and wave height show that this coupling model performs well to reflect the characteristics of the water levels and waves in the studied region.Results show that the effect of radiation stress on storm surge is significant, especially in shallow areas such as the coast of Jiangsu Province and the Yangtze estuary.By running the coupled model, the simulated potential flooding results can be employed in coastal engineering applications in the Jiangsu coastal area, such as storm surge warnings and extreme water level predictions.展开更多
The landfall process of typhoon Haitang which affected East China seriously was simulated by using the MM5 model and the track, intensity, precipitation and structure of typhoon were successfully reproduced. Then thro...The landfall process of typhoon Haitang which affected East China seriously was simulated by using the MM5 model and the track, intensity, precipitation and structure of typhoon were successfully reproduced. Then through the sensitive test, the effects of terrain were analyzed Results show that the irregular track during the period of typhoon passing through Taiwan and later landfalling at Fujian was in relation to the occurring and developing of orthographic impressed depression. The amount of rainfall was enhanced more than one time and the strength of typhoon was weakened 4 to 5 hPa. It is found that the effect of terrain on the structure of typhoon is limited at low level and is backward in space compared with the one at high level. In addition, the phenomenon that the equivalent temperature in the typhoon＇s moving direction inclines to the west on the eye of landfall may be concerned with the terrain.展开更多
Using typhoon data over the Northwestern Pacific （NWP） in 60 years （1950-2009）, the interdecadal variations of typhoon frequency, track and intensity are statistically analyzed. The results showed that the frequen...Using typhoon data over the Northwestern Pacific （NWP） in 60 years （1950-2009）, the interdecadal variations of typhoon frequency, track and intensity are statistically analyzed. The results showed that the frequency of typhoon over the NWP was high in 1960s and low in 1970s. From the late 1990s, the frequency is low again. The track of typhoon was mainly shifting, and the average track was at the southern NWP in 1960s and 1970s, but in recent 10 years, the track was at the northern NWP. The intensity of typhoon was strong in 1950s and 1960s, but becomes weak in recent 25 years. In high frequency periods of typhoon, the subtropical high of NWP was weak and its position appears easternly. The distribution of Sea Surface Temperature （SST） shows characteristics of ＂La Nina＂ event. In low frequency periods of typhoon, the subtropical high of NWP is strong and its position appears westernly. The distribution of SST shows characteristics of ＂El Nino＂ event.展开更多
In this paper, the adjoint method is applied to the statistical-dynamic model （SD-90） for the prediction of typhoon tracks along with the regularization thinking and optimal control techniques. The adjoint model and...In this paper, the adjoint method is applied to the statistical-dynamic model （SD-90） for the prediction of typhoon tracks along with the regularization thinking and optimal control techniques. The adjoint model and the gradient of objective function are deduced with the continual model respectively. For 4 typical typhoons, the forces and the initial velocity can be retrieved well, and the tracks of these typhoons are accurately fitted for an appropriate regularization parameter and optimal control parameter.展开更多
Using T106 numerical products, MM5 simulations in conjunction of Q-vector scheme-computed NCEP results, observations and satellite cloud images, study is undertaken for an exceptionally intense rainstorm event afflict...Using T106 numerical products, MM5 simulations in conjunction of Q-vector scheme-computed NCEP results, observations and satellite cloud images, study is undertaken for an exceptionally intense rainstorm event afflicting the Wenzhou region of Zhejiang province far away from the tropical storm center happening early on the morning of September 4, 1999 （TS9909 hereinafter）. Evidence suggests that, like previously-studied typhoons landing in autumn south of Xiamen to the eastern part of Guangdong, TS9909 has an inverted trough in the central south of the coastal belt of Zhejiang province that produces the rainstorm from the meso convective complex （MCC） on the warm, moist shear inside; the time and order of the magnitude of the rainfall are bound up with the development of the pattern of strong Q-vector divergence gradients during the event for the study area; the NE - SW coastline and the unique topography of the Yandang mountains inside the region are favorable for air lifting are the major contributors to the torrential rains.展开更多
Daniau Village in Daniau Creek Watershed, Taitung County, Taiwan, sustained damages from landslides and mudflows during Typhoon Morakot in 2009. The purpose of this study is to adopt the FLO-2D numerical model recogni...Daniau Village in Daniau Creek Watershed, Taitung County, Taiwan, sustained damages from landslides and mudflows during Typhoon Morakot in 2009. The purpose of this study is to adopt the FLO-2D numerical model recognized by Federal Emergency Management Agency （FEMA） to simulate the mudflow, and the Daniau Village was used as a case study, along with rainfall and digital terrain data for this simulation. On the basis of sediment yields, the residual sediment volume in the landslide area was determined to be 33,276 ma by comparison of digital elevation models （DEMs） and by using the universal soil loss equation （USLE）. In addition, this study performed a hydrological frequency analysis of rainfall to estimate the flow discharge as conditions of the simulation. Results of disaster surveys were collected to compare with outputs of the numerical model. Results of the simulation conducted with FLO- 2D indicated that if the countermeasure was not destroyed, the drainage work would function without overflow. This study aimed to review the effectiveness of eountermeasure on the basis of simulation results obtained by using the model to provide references for future disaster prevention and resident evacuation plans.展开更多
Using real analysis data of 1°×1° resolution of the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR),the nondivergent wind component and irrotational win...Using real analysis data of 1°×1° resolution of the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR),the nondivergent wind component and irrotational wind component obtained by the harmonic-cosine(H-C) method,and the wind structure of Typhoon Fung-Wong (coded 0808 in China) in 2008 was analyzed. The results indicated that the irrotational component was advantageous over the total wind in reflecting both the changes in convergent height and the asymmetrical convergence of Fung-Wong. In Fung-Wong,the nondivergent component was larger than the irrotational component,but the latter was much more variable than the former,which was obtained only from the wind partition method. Further analyses on the irrotational component demonstrated that the location of the convergent center at lower levels was almost the same as the divergent center during the development of Fung-Wong,and its convergent level was high in its life cycle,with the most highest up to 400 hPa when it became stronger. After the typhoon landed in the provinces of Taiwan and Fujian,respectively,its convergent center at lower levels was slowly detached from the divergent center at high levels and the convergent height was also depressed from high levels to lower levels. Gradually,this weakened the intensity of Fung-Wong. This kind of weakening was slow and Fung-Wong maintained its circulation for a long time over land because of its very thick convergent height. Analyses on wind partitioning provided one possible explanation to why Fung-Wong stayed for a long time after it landed. Furthermore,the asymmetric vertical ascending motion was induced by the asymmetric convergence at lower levels. In general,when typhoons (such as Fung-Wong) land,the rainfall region coincides with that of the convergence region (indicated by the irrotational component at lower layers). This means that the possible rainfall regions may be diagnosed from the convergent area of the irrotational component. For an observational experiment on typhoons,the convergent region may be considered as a key observational region.展开更多
The impact of terrains on the precipitation of landfalling typhoon Talim (2005) over China's Mainland is investigated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Resear...The impact of terrains on the precipitation of landfalling typhoon Talim (2005) over China's Mainland is investigated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model. The simulated precipitation of simulated typhoon (the control) matches the observations closely. To compare with the control simulation, four sensitivity simulations were carried out in which terrains of Wuyi Mountain, Lushan, Dabieshan, and both Lushan and Dabieshan are completely removed respectively, but other surface properties were retained. It is found that the complex terrains of Wuyi Mountain, Lushan and Dabieshan have a significant impact on the rainfall intensity and distribution of Talim. As the terrains are removed, the rainfall is decreased very greatly and the rainfall in inland area is decreased much more than that in the coastal area. Besides, the rainfall distribution near the Lushan and Dabieshan is spread much more westward compared with the control simulation. Further analysis shows that the Wuyi Mountain would increase both the lower level air convergence and the upper level air divergence for Talim that just made landfall and thus it would contribute to the convection and increase rainfall intensity. It can be concluded that the terrains of Wuyi Mountain, Lushan and Dabieshan have obvious impacts on the Talim rainfall, and their impacts are different in various landfalling periods. The present study is a useful attempt to explore the influence of orography on the TCs in China's Mainland.展开更多
Axisymmetric bogus vortexes at sea level are usually used in the traditional bogus data assimilation （BDA） scheme. In the traditional scheme, the vortex could not accurately describe the specific characteristics of ...Axisymmetric bogus vortexes at sea level are usually used in the traditional bogus data assimilation （BDA） scheme. In the traditional scheme, the vortex could not accurately describe the specific characteristics of a typhoon, and the evolving real typhoon is forced to unreasonably adapt to this changeless vortex. For this reason, an asymmetrical typhoon bogus method with information blended from the analysis and the observation is put forward in this paper, in which the impact of the Subtropical High is also taken into consideration. With the fifth-generation Penn State/NCAR Mesoscale Model （MM5） and its adjoint model, a four-dimensional variational data assimilation （4D-Var） technique is employed to build a dynamic asymmetrical BDA scheme to assimilate different asymmetrical bogus vortexes at different time. The track and intensity of six surmner typhoons much influenced by the Subtropical High are simulated and the results are compared. It is shown that the improvement in track simulation in the new scheme is more significant than that in the traditional scheme. Moreover, the periods for which the track cannot be simulated well by the traditional scheme can be improved with the new scheme. The results also reveal that although the simulated typhoon intensity in the new scheme is generally weaker than that in the traditional scheme, this trend enables the new scheme to simulate, in the later period, closer-to-observation intensity than the traditional scheme. However, despite the fact that the observed intensity has been largely weakened, the simulated intensity at later periods of the BDA schemes is still very intensive, resulting in overly development of the typhoon during the simulation. The limitation to the simulation effect of the BDA scheme due to this condition needs to be further studied.展开更多
文摘Wave fields in Beibu Bay during Typhoon Damrey （2005） were simulated by SWAN wave model through inputting high resolution reanalysis wind fields data, current and water level data. Comparisons for wind input and wave hindcast between observation and simulation show good consistency. Distributions of wave parameters such as wave height, wave period, wave length and wave direction under typhoon wind forcing were given. Also, the directional spectra related to the different position from the typhoon center were discussed. And at last, the variation and characteristics of observed frequency spectrum during the passage of Damrey were presented.
基金The National High Technology Research and Development Program of China (863Program) (No.2006AA04Z416)the Key Project of the National Natural Science Foundation of China(No.50538020)+2 种基金the National Science Fund for Distinguished Young Scholars(No.50725828)the National Natural Science Foundation of China for Young Scholars(No.50608017)the Ph.D. Programs Foundation of Ministry of Education of China (No.200802861012)
文摘The strong wind characteristics of the Runyang Suspension Bridge（ RSB） including the wind speed and direction, the turbulence intensity, the turbulence integral length and power spectrum are analyzed based on measurement data from the wind environment monitoring subsystem of the structural health monitoring system （SHMS）of the RSB and field tests during strong winds. The differences between the typhoon and the strong northern wind are especially studied. It is found that the mean wind speed of the strong northern wind is a little smaller and the mean wind direction is more stable than that of the typhoon. The turbulence intensity of both the typhoon and the strong northern wind is greater than the values suggested in Chinese code, and the turbulence integral length difference between the typhoon and a strong northern wind is not clear. As for the along-wind turbulence power spectrum, the spectrum of the strong northern wind can fit the Kaimal spectrum better than that of the typhoon. The obtained results can provide measurement data for founding a strong wind characteristic database and determining the strong wind characteristic parameter values of the RSB.
基金The National Natural Science Foundation of China(No.51209040,51279134)the Natural Science Foundation of Jiangsu Province(No.BK2012341)+1 种基金the Fundamental Research Funds for the Central Universities(No.SJLX_0087)the Research Fund of Nanjing Hydraulic Research Institute(No.Y213012)
文摘In order to facilitate engineering design and coastal flooding protection, the potential storm surge induced by a typhoon is studied.Using an unstructured mesh, a coupled model which combines the advanced circulation （ ADCIRC ） hydrodynamic model and simulating waves nearshore （ SWAN ） model is applied to analyze the storm surge and waves on the coast of Jiangsu Province.The verifications of wind velocity, tidal levels and wave height show that this coupling model performs well to reflect the characteristics of the water levels and waves in the studied region.Results show that the effect of radiation stress on storm surge is significant, especially in shallow areas such as the coast of Jiangsu Province and the Yangtze estuary.By running the coupled model, the simulated potential flooding results can be employed in coastal engineering applications in the Jiangsu coastal area, such as storm surge warnings and extreme water level predictions.
文摘The landfall process of typhoon Haitang which affected East China seriously was simulated by using the MM5 model and the track, intensity, precipitation and structure of typhoon were successfully reproduced. Then through the sensitive test, the effects of terrain were analyzed Results show that the irregular track during the period of typhoon passing through Taiwan and later landfalling at Fujian was in relation to the occurring and developing of orthographic impressed depression. The amount of rainfall was enhanced more than one time and the strength of typhoon was weakened 4 to 5 hPa. It is found that the effect of terrain on the structure of typhoon is limited at low level and is backward in space compared with the one at high level. In addition, the phenomenon that the equivalent temperature in the typhoon＇s moving direction inclines to the west on the eye of landfall may be concerned with the terrain.
文摘Using typhoon data over the Northwestern Pacific （NWP） in 60 years （1950-2009）, the interdecadal variations of typhoon frequency, track and intensity are statistically analyzed. The results showed that the frequency of typhoon over the NWP was high in 1960s and low in 1970s. From the late 1990s, the frequency is low again. The track of typhoon was mainly shifting, and the average track was at the southern NWP in 1960s and 1970s, but in recent 10 years, the track was at the northern NWP. The intensity of typhoon was strong in 1950s and 1960s, but becomes weak in recent 25 years. In high frequency periods of typhoon, the subtropical high of NWP was weak and its position appears easternly. The distribution of Sea Surface Temperature （SST） shows characteristics of ＂La Nina＂ event. In low frequency periods of typhoon, the subtropical high of NWP is strong and its position appears westernly. The distribution of SST shows characteristics of ＂El Nino＂ event.
基金The National Nature Science Foundation of China under Grant No.90411006 supported this work simultaneously.
文摘In this paper, the adjoint method is applied to the statistical-dynamic model （SD-90） for the prediction of typhoon tracks along with the regularization thinking and optimal control techniques. The adjoint model and the gradient of objective function are deduced with the continual model respectively. For 4 typical typhoons, the forces and the initial velocity can be retrieved well, and the tracks of these typhoons are accurately fitted for an appropriate regularization parameter and optimal control parameter.
基金sponsored jointly by the Natural Science Foundation of China (Grant 4040950009402050084)the Project of Planned National Key Basic Research/Development (2004CB418301)
文摘Using T106 numerical products, MM5 simulations in conjunction of Q-vector scheme-computed NCEP results, observations and satellite cloud images, study is undertaken for an exceptionally intense rainstorm event afflicting the Wenzhou region of Zhejiang province far away from the tropical storm center happening early on the morning of September 4, 1999 （TS9909 hereinafter）. Evidence suggests that, like previously-studied typhoons landing in autumn south of Xiamen to the eastern part of Guangdong, TS9909 has an inverted trough in the central south of the coastal belt of Zhejiang province that produces the rainstorm from the meso convective complex （MCC） on the warm, moist shear inside; the time and order of the magnitude of the rainfall are bound up with the development of the pattern of strong Q-vector divergence gradients during the event for the study area; the NE - SW coastline and the unique topography of the Yandang mountains inside the region are favorable for air lifting are the major contributors to the torrential rains.
基金supported in part by the National Science Council (NSC 97-2313-B-270-001-MY3) and Taitung Branch,Soil and Water Conservation Bureau, Council of Agriculture,Taiwan
文摘Daniau Village in Daniau Creek Watershed, Taitung County, Taiwan, sustained damages from landslides and mudflows during Typhoon Morakot in 2009. The purpose of this study is to adopt the FLO-2D numerical model recognized by Federal Emergency Management Agency （FEMA） to simulate the mudflow, and the Daniau Village was used as a case study, along with rainfall and digital terrain data for this simulation. On the basis of sediment yields, the residual sediment volume in the landslide area was determined to be 33,276 ma by comparison of digital elevation models （DEMs） and by using the universal soil loss equation （USLE）. In addition, this study performed a hydrological frequency analysis of rainfall to estimate the flow discharge as conditions of the simulation. Results of disaster surveys were collected to compare with outputs of the numerical model. Results of the simulation conducted with FLO- 2D indicated that if the countermeasure was not destroyed, the drainage work would function without overflow. This study aimed to review the effectiveness of eountermeasure on the basis of simulation results obtained by using the model to provide references for future disaster prevention and resident evacuation plans.
基金State Key Development Program for Basic Research of China (2009CB421505)Project of the Ministry of Sciences and Technology of the People’s Republic of China (GYHY200706020)+1 种基金Projects of the Natural Science Foundation of China (40975034, 40775031)Open Project of State Key Laboratory of Severe Weather (2008LASW-A01)
文摘Using real analysis data of 1°×1° resolution of the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR),the nondivergent wind component and irrotational wind component obtained by the harmonic-cosine(H-C) method,and the wind structure of Typhoon Fung-Wong (coded 0808 in China) in 2008 was analyzed. The results indicated that the irrotational component was advantageous over the total wind in reflecting both the changes in convergent height and the asymmetrical convergence of Fung-Wong. In Fung-Wong,the nondivergent component was larger than the irrotational component,but the latter was much more variable than the former,which was obtained only from the wind partition method. Further analyses on the irrotational component demonstrated that the location of the convergent center at lower levels was almost the same as the divergent center during the development of Fung-Wong,and its convergent level was high in its life cycle,with the most highest up to 400 hPa when it became stronger. After the typhoon landed in the provinces of Taiwan and Fujian,respectively,its convergent center at lower levels was slowly detached from the divergent center at high levels and the convergent height was also depressed from high levels to lower levels. Gradually,this weakened the intensity of Fung-Wong. This kind of weakening was slow and Fung-Wong maintained its circulation for a long time over land because of its very thick convergent height. Analyses on wind partitioning provided one possible explanation to why Fung-Wong stayed for a long time after it landed. Furthermore,the asymmetric vertical ascending motion was induced by the asymmetric convergence at lower levels. In general,when typhoons (such as Fung-Wong) land,the rainfall region coincides with that of the convergence region (indicated by the irrotational component at lower layers). This means that the possible rainfall regions may be diagnosed from the convergent area of the irrotational component. For an observational experiment on typhoons,the convergent region may be considered as a key observational region.
基金State 973 Program (2009CB421505)National Natural Sciences Foundation of China (40405012+3 种基金 40830958 40705024)Ministry of Science and Technology of China (2005DIB3J104)Shanghai Typhoon Research Foundation (2009ST11)
文摘The impact of terrains on the precipitation of landfalling typhoon Talim (2005) over China's Mainland is investigated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model. The simulated precipitation of simulated typhoon (the control) matches the observations closely. To compare with the control simulation, four sensitivity simulations were carried out in which terrains of Wuyi Mountain, Lushan, Dabieshan, and both Lushan and Dabieshan are completely removed respectively, but other surface properties were retained. It is found that the complex terrains of Wuyi Mountain, Lushan and Dabieshan have a significant impact on the rainfall intensity and distribution of Talim. As the terrains are removed, the rainfall is decreased very greatly and the rainfall in inland area is decreased much more than that in the coastal area. Besides, the rainfall distribution near the Lushan and Dabieshan is spread much more westward compared with the control simulation. Further analysis shows that the Wuyi Mountain would increase both the lower level air convergence and the upper level air divergence for Talim that just made landfall and thus it would contribute to the convection and increase rainfall intensity. It can be concluded that the terrains of Wuyi Mountain, Lushan and Dabieshan have obvious impacts on the Talim rainfall, and their impacts are different in various landfalling periods. The present study is a useful attempt to explore the influence of orography on the TCs in China's Mainland.
基金Natural Science Foundation of China (10871099 40805046+2 种基金 40830958)Specialized Projects of Public Welfare Industry (Meteorological Sector) (GYH(QX)2007-6-15)973 Program of National Key Foundamental Research and Development (2009CB421502)
文摘Axisymmetric bogus vortexes at sea level are usually used in the traditional bogus data assimilation （BDA） scheme. In the traditional scheme, the vortex could not accurately describe the specific characteristics of a typhoon, and the evolving real typhoon is forced to unreasonably adapt to this changeless vortex. For this reason, an asymmetrical typhoon bogus method with information blended from the analysis and the observation is put forward in this paper, in which the impact of the Subtropical High is also taken into consideration. With the fifth-generation Penn State/NCAR Mesoscale Model （MM5） and its adjoint model, a four-dimensional variational data assimilation （4D-Var） technique is employed to build a dynamic asymmetrical BDA scheme to assimilate different asymmetrical bogus vortexes at different time. The track and intensity of six surmner typhoons much influenced by the Subtropical High are simulated and the results are compared. It is shown that the improvement in track simulation in the new scheme is more significant than that in the traditional scheme. Moreover, the periods for which the track cannot be simulated well by the traditional scheme can be improved with the new scheme. The results also reveal that although the simulated typhoon intensity in the new scheme is generally weaker than that in the traditional scheme, this trend enables the new scheme to simulate, in the later period, closer-to-observation intensity than the traditional scheme. However, despite the fact that the observed intensity has been largely weakened, the simulated intensity at later periods of the BDA schemes is still very intensive, resulting in overly development of the typhoon during the simulation. The limitation to the simulation effect of the BDA scheme due to this condition needs to be further studied.
