Air-sea interaction usually affects the distribution of precipitation during typhoon period, but whether typhoon precipitation distribution is affected by ocean eddies is still unclear. In this study, based on a multi...Air-sea interaction usually affects the distribution of precipitation during typhoon period, but whether typhoon precipitation distribution is affected by ocean eddies is still unclear. In this study, based on a multi-source satellite database, reanalysis data and in-situ data were used to study the precipitation characteristics of Typhoon Lekima (2019) as well as its physical causes. The results showed that the precipitation of Lekima presents an asymmetric structure, exhibiting heavier precipitation on the left side of the typhoon path before 7 August, and with the typhoon strengthened, precipitation was evenly distributed around the typhoon center. The typhoon cloud system, characteristics of the typhoon, and ocean factors could be responsible for the asymmetric structure of precipitation during the typhoon period. The change in the typhoon cloud system during the typhoon influenced the distribution of precipitation. And there have been some oceanic processes that influenced the distribution of precipitation. Anticyclonic eddies and thick mixing level depths (MLDs) play important roles in typhoon precipitation. The anticyclonic eddies with thick MLD exist to reduce the mixing of the upper ocean to maintain the SST. Therefore, the SST and air-sea exchange can be sustained to influence typhoon precipitation. This study provides a new understanding of the impact of ocean processes on typhoon precipitation distribution.展开更多
During the period of the super typhoon"Lekima"(No.1909)landed on the coast of North China,a high-resolution numerical simulation study was carried out with the WRF model on the clouds microphysical process o...During the period of the super typhoon"Lekima"(No.1909)landed on the coast of North China,a high-resolution numerical simulation study was carried out with the WRF model on the clouds microphysical process of heavy precipitation.The results showed that(1)the water vapor convergence tended to develop and strengthen on the way forward of typhoon center,and the evolution of water vapor convergence zone was closely related to the development of typhoon asymmetric structure,and had a good corresponding relationship with the falling zone of the rainstorm.(2)The eastern coast of Hebei was located in the big-value area of water vapor transport belt in the northwest quadrant of the typhoon.Below 850 hPa,northeast wind appeared,and warm humid water vapor was transported from marine area to terrestrial by typhoon.Affected by upper-level westerly trough,westerly wind was dominated above 700 hPa,and water vapor convergence was transported from low level to upper level,and several rainstorm center appeared.(3)In the spiral rain bands of typhoon,the big-value center of graupel particles cooperated with the warm cloud enriched with water content,and the ground would produce a center of heavy precipitation,and the precipitation center of pure warm cloud appeared in 117.5°E.This phenomenon rarely occurred during continental cloud precipitation.Therefore,the contribution of warm cloud precipitation mechanism to the typhoon spiral rain belt should be emphasized.展开更多
This study undertook verification of the applicability and accuracy of wind data measured using a WindCube V2 Doppler Wind Lidar(DWL).The data were collected as part of a field experiment in Zhoushan,Zhejiang Province...This study undertook verification of the applicability and accuracy of wind data measured using a WindCube V2 Doppler Wind Lidar(DWL).The data were collected as part of a field experiment in Zhoushan,Zhejiang Province(China),which was conducted by Shanghai Typhoon Institute of China Meteorological Administration during the passage of Super Typhoon Lekima(2019).The DWL measurements were compared with balloon-borne GPS radiosonde(GPS sonde)data,which were acquired using balloons launched from the DWL location.Results showed that wind speed measured by GPS sonde at heights of<100 m is unreliable owing to the drift effect.Optimal agreement(at heights of>100 m)was found for DWL-measured wind speed time-averaged during the ascent of the GPS sonde from the ground surface to the height of 270 m(correlation coefficient:0.82;root mean square(RMS):2.19 m·h^(-1)).Analysis revealed that precipitation intensity(PI)exerts considerable influence on both the carrier-to-noise ratio and the rate of missing DWL data;however,PI has minimal effect on the wind speed bias of DWL measurements.Specifically,the rate of missing DWL data increased with increasing measurement height and PI.For PI classed as heavy rain or less(PI<12 mm·h^(-1)),the DWL data below 300 m were considered valid,whereas for PI classed as a severe rainstorm(PI>90 m·h^(-1)),only data below 100 m were valid.Up to the height of 300 m,the RMS of the DWL measurements was nearly half that of wind profile radar(WPR)estimates(4.32 m·s^(-1)),indicating that DWL wind data are more accurate than WPR data under typhoon conditions.展开更多
The typhoon is one major threat to human societies and natural ecosystems, and its risk perception is crucial for contextualizing and managing disaster risks in different social settings. Social media data are a new d...The typhoon is one major threat to human societies and natural ecosystems, and its risk perception is crucial for contextualizing and managing disaster risks in different social settings. Social media data are a new data source for studying risk perception, because such data are timely, widely distributed, and sensitive to emergencies.However, few studies have focused on crowd sensitivity variation in social media data-based typhoon risk perception. Based on the regional disaster system theory, a framework of analysis for crowd risk perception was established to explore the feasibility of using social media data for typhoon risk perception analysis and crowd sensitivity variation. The goal was to quantitatively analyze the impact of hazard intensity and social and geographical environments on risk perception and its variation among population groups. Taking the Sina Weibo data during Typhoon Lekima of 2019 as an example, we found that:(1)Typhoon Lekima-related Weibo public attention changed in accordance with the evolution of the typhoon track and the number of Weibo posts shows a significantly positive correlation with disaster losses, while socioeconomic factors,including population, gross domestic product, and land area, are not explanatory factors of the spatial distribution of disaster-related Weibo posts;(2) Females, nonlocals with travel plans, and people living in areas with high hazard intensity, low elevation, or near waterbodies affected by Lekima paid more attention to the typhoon disaster;and(3)Descriptions of rainfall intensity by females are closer to the meteorological observation data.展开更多
The rainfall forecast performance of the Tropical Cyclone(TC)version Model of Global and Regional Assimilation PrEdiction System(GRAPESTCM)of the China Meteorological Administration for landfalling Super Typhoon Lekim...The rainfall forecast performance of the Tropical Cyclone(TC)version Model of Global and Regional Assimilation PrEdiction System(GRAPESTCM)of the China Meteorological Administration for landfalling Super Typhoon Lekima(2019)is studied by using the object-oriented verification method of contiguous rain area(CRA).The major error sources and possible reasons for the rainfall forecast uncertainties in different landfall stages(including near landfall and moving further inland)are compared.Results show that different performance and errors of rainfall forecast exist in the different TC stages.In the near landfall stage the asymmetric rainfall distribution is hard to be simulated,which might be related to the too strong forecasted TC intensity and too weak vertical wind shear accompanied.As Lekima moves further inland,the rain pattern and volume errors gradually increase.The Equitable Threat Score of the 24 h forecasted rainfall over 100 mm declines quickly with the time-length over land.The diagnostic analysis shows that there exists an interaction between the TC and the mid-latitude westerlies,but too weak frontogenesis is simulated.The results of this research indicate that for the current numerical model,the forecast ability of persistent heavy rainfall is very limited,especially when the weakened landing TC moves further inland.展开更多
The predictions for Super Typhoon Lekima(2019)have been evaluated from official forecasts,global models,regional models and ensemble prediction systems(EPSs)at lead times of 1–5 days.Track errors from most determinis...The predictions for Super Typhoon Lekima(2019)have been evaluated from official forecasts,global models,regional models and ensemble prediction systems(EPSs)at lead times of 1–5 days.Track errors from most deterministic forecasts are smaller than their annual mean errors in 2019.Compared to the propagation speed,the propagation direction of Lekima(2019)was much easier to determine for the official agency and numerical weather prediction(NWP)models.The National Centers for Environmental Prediction Global Ensemble Forecast System(NCEP-GEFS),Japan Meteorological Agency Global Ensemble Prediction System(JMA-GEPS)and Meteorological Service of Canada Ensemble System(MSC-CENS)are underdispersed,and the Shanghai Typhoon Institute Typhoon Ensemble Data Assimilation and Prediction System(STI-TEDAPS)is overdispersed,while the ensemble prediction system from European Centre for Medium-Range Weather Forecasts(ECMWF)shows adequate dispersion at all lead times.Most deterministic forecasting methods underestimated the intensity of Lekima(2019),especially for the rapid intensification period after Lekima(2019)entered the East China Sea.All of the deterministic forecasts performed well at predicting the first landfall point at Wenling,Zhejiang Province with a lead time of 24 and 48 h.展开更多
Why does the 1909 typhoon,Lekima,become so destructive after making landfall in China?Using a newly developed mathematical apparatus,the multiscale window transform(MWT),and the MWT-based localized mutliscale energeti...Why does the 1909 typhoon,Lekima,become so destructive after making landfall in China?Using a newly developed mathematical apparatus,the multiscale window transform(MWT),and the MWT-based localized mutliscale energetics analysis and theory of canonical transfer,this study is intended to give a partial answer from a dynamical point of view.The ECMWF reanalysis fields are first reconstructed onto the background window,the TC-scale window,and the convection-scale window.A localized energetics analysis is then performed,which reveals to us distinctly different scenarios before and after August 8–9,2019,when an eyewall replacement cycle takes place.Before that,the energy supply in the upper layer is mainly via a strong upper layer-limited baroclinic instability;the available potential energy thus-gained is then converted into the TC-scale kinetic energy,with a portion to fuel Lekima’s upper part,another portion carried downward via pressure work flux to maintain the cyclone’s lower part.After the eyewall replacement cycle,a drastic change in dynamics occurs.First,the pressure work is greatly increased in magnitude.A positive baroclinic transfer almost spreads throughout the troposphere,and so does barotropic transfer;in other words,the whole air column is now both barotropically and baroclinically unstable.These newly occurred instabilities help compensate the increasing consumption of the TC-scale kinetic energy,and hence help counteract the dissipation of Lekima after making landfalls.展开更多
Typhoon Lekima(2019)struck Zhejiang Province on 10 August 2019 as a supertyphoon,which severely impacted Zhejiang Province.The typhoon killed 45 people and left three others missing,and the total economic loss reached...Typhoon Lekima(2019)struck Zhejiang Province on 10 August 2019 as a supertyphoon,which severely impacted Zhejiang Province.The typhoon killed 45 people and left three others missing,and the total economic loss reached 40.71 billion yuan.This paper reports a postdisaster survey that focuses on the storm precipitation,flooding,landslides,and weather services associated with Typhoon Lekima(2019)along the southeastern coastline of Zhejiang Province.The survey was conducted by a joint survey team from the Shanghai Typhoon Institute and local meteorological bureaus from 26 to 28 August,2019,approximately two weeks after the disaster.Based on this survey and subsequent analyses of the results,we hope to develop countermeasures to prevent future tragedies.展开更多
Recent developments in process-based coastal area models such as XBeach provide new opportunities to predict coastal responses to primary forcing mechanisms such as storm hydrodynamic by using 2DH grids.However,due to...Recent developments in process-based coastal area models such as XBeach provide new opportunities to predict coastal responses to primary forcing mechanisms such as storm hydrodynamic by using 2DH grids.However,due to the lack of measured data,there are few application scenarios of the models.Therefore,more measurement and research are needed.In this paper,the Typhoon Lekima that hitting Zhejiang Province during neap tide period was selected to simulate morphodynamic responses of the Huangcheng Beach by assuming encountering with different tide types.Cross shore measurements with eight cross-shore profiles(named S1~S8 from north to south)of the Huangcheng Beach pre-and post-the Typhoon Lekima respectively were presented.Then a 2DH storm surge and wave coupled model was established with Delft3D Flow/Wave.The model was well calibrated with measured water levels and wave data and provided hydrodynamic boundary conditions of different typhoon and tide types coupling situations for a refined model.The refined model was built using XBeach and simulated the morphological responses of the Huangcheng beach with well verifications.On basis of the numerical results,bed level changes at the eight profiles were analyzed,and the character of erosion and deposition under different tide conditions were illustrated.The net sand volume changes were got smaller under the spring tide condition rather than middle tide and neap tide conditions.Further study of the distribution of wave induced current at different stages of collision,inundation and ebb shown that the stronger current under spring tide condition would increase the sediment transport rate and reduce the deposition volume at profiles S3 and S6~S8,and the total amount of sediment involved in transportation had increased for the whole beach,leading to the reduction of net erosion volume at profiles S1,S2,S4 and S5.展开更多
本文对海洋气象漂流观测仪实测、CMA最佳路径数据集、第5代全球气象再分析产品(ERA5)、交叉检验多平台融合矢量风场(CCMP)四种资料的海面风在超强台风“利奇马”期间的变化特征进行分析。ERA5、CCMP两种分析/再分析风资料与实测风的对...本文对海洋气象漂流观测仪实测、CMA最佳路径数据集、第5代全球气象再分析产品(ERA5)、交叉检验多平台融合矢量风场(CCMP)四种资料的海面风在超强台风“利奇马”期间的变化特征进行分析。ERA5、CCMP两种分析/再分析风资料与实测风的对比分析表明:(1)风速:当风力<10级时,漂流观测仪轨迹上的ERA5、CCMP风速较漂流观测仪实测风速偏小;将漂流观测仪实测风速订正到10 m高度,风力≤5级时偏差(Bias)绝对值最小,ERA5(CCMP)为4.3 m s^(-1)(4.6 m s^(-1)),风力为7~9级时Bias绝对值最大,约9.2~10.2 m s^(-1);“利奇马”近中心海域ERA5、CCMP最大风速较CMA最佳路径数据集偏小,ERA5(CCMP)偏小约10.7 m s^(-1)(4.6 m s^(-1));ERA5(CCMP)最大风速极值较CMA最佳路径数据集偏低54.5%(12.7%)。(2)风向:ERA5、CCMP与漂流观测仪实测风向相关系数接近于0;风力≤5级时风向较实测偏右,风力>5级时偏左。(3)ERA5、CCMP风向、风速在“利奇马”近中心海域偏差明显,远离中心海域二者吻合度较高。通过对ERA5、CCMP资料进一步分析发现:CCMP能清楚描述热带气旋风场结构及演变过程,“利奇马”为超强台风时结构参数η=Vr/Vmax分布上有闭合环状结构,表明该区域有环状大风速带;“利奇马”强迫时间T_f分布于移动路径两侧,ERA5(CCMP)最大强迫时间为45 h(54 h)。展开更多
文摘Air-sea interaction usually affects the distribution of precipitation during typhoon period, but whether typhoon precipitation distribution is affected by ocean eddies is still unclear. In this study, based on a multi-source satellite database, reanalysis data and in-situ data were used to study the precipitation characteristics of Typhoon Lekima (2019) as well as its physical causes. The results showed that the precipitation of Lekima presents an asymmetric structure, exhibiting heavier precipitation on the left side of the typhoon path before 7 August, and with the typhoon strengthened, precipitation was evenly distributed around the typhoon center. The typhoon cloud system, characteristics of the typhoon, and ocean factors could be responsible for the asymmetric structure of precipitation during the typhoon period. The change in the typhoon cloud system during the typhoon influenced the distribution of precipitation. And there have been some oceanic processes that influenced the distribution of precipitation. Anticyclonic eddies and thick mixing level depths (MLDs) play important roles in typhoon precipitation. The anticyclonic eddies with thick MLD exist to reduce the mixing of the upper ocean to maintain the SST. Therefore, the SST and air-sea exchange can be sustained to influence typhoon precipitation. This study provides a new understanding of the impact of ocean processes on typhoon precipitation distribution.
基金Supported by Bohai Rim Regional Science and Technology Collaborative Innovation Fund(QYXM202004)Hebei Provincial Science and Technology Plan(19275420D)"Cloud Precipitation Physics Aircraft Detection and Application Innovation Team"Project of Hebei Province Weather Modification Office.
文摘During the period of the super typhoon"Lekima"(No.1909)landed on the coast of North China,a high-resolution numerical simulation study was carried out with the WRF model on the clouds microphysical process of heavy precipitation.The results showed that(1)the water vapor convergence tended to develop and strengthen on the way forward of typhoon center,and the evolution of water vapor convergence zone was closely related to the development of typhoon asymmetric structure,and had a good corresponding relationship with the falling zone of the rainstorm.(2)The eastern coast of Hebei was located in the big-value area of water vapor transport belt in the northwest quadrant of the typhoon.Below 850 hPa,northeast wind appeared,and warm humid water vapor was transported from marine area to terrestrial by typhoon.Affected by upper-level westerly trough,westerly wind was dominated above 700 hPa,and water vapor convergence was transported from low level to upper level,and several rainstorm center appeared.(3)In the spiral rain bands of typhoon,the big-value center of graupel particles cooperated with the warm cloud enriched with water content,and the ground would produce a center of heavy precipitation,and the precipitation center of pure warm cloud appeared in 117.5°E.This phenomenon rarely occurred during continental cloud precipitation.Therefore,the contribution of warm cloud precipitation mechanism to the typhoon spiral rain belt should be emphasized.
基金supported by the National Key R&D Program of China(No.2018YFB1501104)Key Program for International S&T Cooperation Projects of China(No.2017YFE0107700)+1 种基金National Natural Science Foundation of China(Grant No.41805088)Natural Science Foundation of Shanghai(No.18ZR1449100).
文摘This study undertook verification of the applicability and accuracy of wind data measured using a WindCube V2 Doppler Wind Lidar(DWL).The data were collected as part of a field experiment in Zhoushan,Zhejiang Province(China),which was conducted by Shanghai Typhoon Institute of China Meteorological Administration during the passage of Super Typhoon Lekima(2019).The DWL measurements were compared with balloon-borne GPS radiosonde(GPS sonde)data,which were acquired using balloons launched from the DWL location.Results showed that wind speed measured by GPS sonde at heights of<100 m is unreliable owing to the drift effect.Optimal agreement(at heights of>100 m)was found for DWL-measured wind speed time-averaged during the ascent of the GPS sonde from the ground surface to the height of 270 m(correlation coefficient:0.82;root mean square(RMS):2.19 m·h^(-1)).Analysis revealed that precipitation intensity(PI)exerts considerable influence on both the carrier-to-noise ratio and the rate of missing DWL data;however,PI has minimal effect on the wind speed bias of DWL measurements.Specifically,the rate of missing DWL data increased with increasing measurement height and PI.For PI classed as heavy rain or less(PI<12 mm·h^(-1)),the DWL data below 300 m were considered valid,whereas for PI classed as a severe rainstorm(PI>90 m·h^(-1)),only data below 100 m were valid.Up to the height of 300 m,the RMS of the DWL measurements was nearly half that of wind profile radar(WPR)estimates(4.32 m·s^(-1)),indicating that DWL wind data are more accurate than WPR data under typhoon conditions.
基金supported by the National Key Research and Development Program of China(No.2018YFC1508903)the Science Technology Department of Zhejiang Province(No.2022C03107)the International Center for Collaborative Research on Disaster Risk Reduction。
文摘The typhoon is one major threat to human societies and natural ecosystems, and its risk perception is crucial for contextualizing and managing disaster risks in different social settings. Social media data are a new data source for studying risk perception, because such data are timely, widely distributed, and sensitive to emergencies.However, few studies have focused on crowd sensitivity variation in social media data-based typhoon risk perception. Based on the regional disaster system theory, a framework of analysis for crowd risk perception was established to explore the feasibility of using social media data for typhoon risk perception analysis and crowd sensitivity variation. The goal was to quantitatively analyze the impact of hazard intensity and social and geographical environments on risk perception and its variation among population groups. Taking the Sina Weibo data during Typhoon Lekima of 2019 as an example, we found that:(1)Typhoon Lekima-related Weibo public attention changed in accordance with the evolution of the typhoon track and the number of Weibo posts shows a significantly positive correlation with disaster losses, while socioeconomic factors,including population, gross domestic product, and land area, are not explanatory factors of the spatial distribution of disaster-related Weibo posts;(2) Females, nonlocals with travel plans, and people living in areas with high hazard intensity, low elevation, or near waterbodies affected by Lekima paid more attention to the typhoon disaster;and(3)Descriptions of rainfall intensity by females are closer to the meteorological observation data.
基金supported in part by Key Program for International S&T Cooperation Projects of China(No.2017YFE0107700)the National Natural Science Foundation of China(Grant No.41875080)+1 种基金Scientific Research Program of Shanghai Science and Technology Commission(No.19dz1200101)in part by Shanghai Talent Development Fund and Fujian Key Laboratory of Severe Weather Open Foundation(2020TFS01).
文摘The rainfall forecast performance of the Tropical Cyclone(TC)version Model of Global and Regional Assimilation PrEdiction System(GRAPESTCM)of the China Meteorological Administration for landfalling Super Typhoon Lekima(2019)is studied by using the object-oriented verification method of contiguous rain area(CRA).The major error sources and possible reasons for the rainfall forecast uncertainties in different landfall stages(including near landfall and moving further inland)are compared.Results show that different performance and errors of rainfall forecast exist in the different TC stages.In the near landfall stage the asymmetric rainfall distribution is hard to be simulated,which might be related to the too strong forecasted TC intensity and too weak vertical wind shear accompanied.As Lekima moves further inland,the rain pattern and volume errors gradually increase.The Equitable Threat Score of the 24 h forecasted rainfall over 100 mm declines quickly with the time-length over land.The diagnostic analysis shows that there exists an interaction between the TC and the mid-latitude westerlies,but too weak frontogenesis is simulated.The results of this research indicate that for the current numerical model,the forecast ability of persistent heavy rainfall is very limited,especially when the weakened landing TC moves further inland.
基金supported in part by the National Nature Science Foundation of China(Grant Nos.41875069 and 41975067)the National Key R&D Program of China(Nos.2018YFC1506406 and 2020YFE0201900)the Shanghai S&T Research Program(No.19dz1200101).
文摘The predictions for Super Typhoon Lekima(2019)have been evaluated from official forecasts,global models,regional models and ensemble prediction systems(EPSs)at lead times of 1–5 days.Track errors from most deterministic forecasts are smaller than their annual mean errors in 2019.Compared to the propagation speed,the propagation direction of Lekima(2019)was much easier to determine for the official agency and numerical weather prediction(NWP)models.The National Centers for Environmental Prediction Global Ensemble Forecast System(NCEP-GEFS),Japan Meteorological Agency Global Ensemble Prediction System(JMA-GEPS)and Meteorological Service of Canada Ensemble System(MSC-CENS)are underdispersed,and the Shanghai Typhoon Institute Typhoon Ensemble Data Assimilation and Prediction System(STI-TEDAPS)is overdispersed,while the ensemble prediction system from European Centre for Medium-Range Weather Forecasts(ECMWF)shows adequate dispersion at all lead times.Most deterministic forecasting methods underestimated the intensity of Lekima(2019),especially for the rapid intensification period after Lekima(2019)entered the East China Sea.All of the deterministic forecasts performed well at predicting the first landfall point at Wenling,Zhejiang Province with a lead time of 24 and 48 h.
基金supported by the National Natural Science Foundation of China(Grant No.41975064)the 2015 Jiangsu Program for Innovation Research and Entrepreneurship Groups.
文摘Why does the 1909 typhoon,Lekima,become so destructive after making landfall in China?Using a newly developed mathematical apparatus,the multiscale window transform(MWT),and the MWT-based localized mutliscale energetics analysis and theory of canonical transfer,this study is intended to give a partial answer from a dynamical point of view.The ECMWF reanalysis fields are first reconstructed onto the background window,the TC-scale window,and the convection-scale window.A localized energetics analysis is then performed,which reveals to us distinctly different scenarios before and after August 8–9,2019,when an eyewall replacement cycle takes place.Before that,the energy supply in the upper layer is mainly via a strong upper layer-limited baroclinic instability;the available potential energy thus-gained is then converted into the TC-scale kinetic energy,with a portion to fuel Lekima’s upper part,another portion carried downward via pressure work flux to maintain the cyclone’s lower part.After the eyewall replacement cycle,a drastic change in dynamics occurs.First,the pressure work is greatly increased in magnitude.A positive baroclinic transfer almost spreads throughout the troposphere,and so does barotropic transfer;in other words,the whole air column is now both barotropically and baroclinically unstable.These newly occurred instabilities help compensate the increasing consumption of the TC-scale kinetic energy,and hence help counteract the dissipation of Lekima after making landfalls.
基金sponsored by the National Natural Science Foundation of China(Grant Nos.41705096,41775065)Key Program for International S&T Cooperation Projects of China(No.2017YFE0107700)+2 种基金National Key R&D Program of China(No.2017YFC1501604)Shanghai Science&Technology Research Program(No.19dz1200101)Fundamental Research Funds of the STI/CMA(No.2019JB06).
文摘Typhoon Lekima(2019)struck Zhejiang Province on 10 August 2019 as a supertyphoon,which severely impacted Zhejiang Province.The typhoon killed 45 people and left three others missing,and the total economic loss reached 40.71 billion yuan.This paper reports a postdisaster survey that focuses on the storm precipitation,flooding,landslides,and weather services associated with Typhoon Lekima(2019)along the southeastern coastline of Zhejiang Province.The survey was conducted by a joint survey team from the Shanghai Typhoon Institute and local meteorological bureaus from 26 to 28 August,2019,approximately two weeks after the disaster.Based on this survey and subsequent analyses of the results,we hope to develop countermeasures to prevent future tragedies.
基金supported by the National Natural Science Foundation of China[Grant No.42076178]the Hydrotechnics Project of Zhejiang Province Department of Water Resources[Grant No.RA2004]and[Grant No.RB2033]the Supporting Funds of Scientific Research Institutions in Zhejiang Province[Grant No.HaiAn A21003].
文摘Recent developments in process-based coastal area models such as XBeach provide new opportunities to predict coastal responses to primary forcing mechanisms such as storm hydrodynamic by using 2DH grids.However,due to the lack of measured data,there are few application scenarios of the models.Therefore,more measurement and research are needed.In this paper,the Typhoon Lekima that hitting Zhejiang Province during neap tide period was selected to simulate morphodynamic responses of the Huangcheng Beach by assuming encountering with different tide types.Cross shore measurements with eight cross-shore profiles(named S1~S8 from north to south)of the Huangcheng Beach pre-and post-the Typhoon Lekima respectively were presented.Then a 2DH storm surge and wave coupled model was established with Delft3D Flow/Wave.The model was well calibrated with measured water levels and wave data and provided hydrodynamic boundary conditions of different typhoon and tide types coupling situations for a refined model.The refined model was built using XBeach and simulated the morphological responses of the Huangcheng beach with well verifications.On basis of the numerical results,bed level changes at the eight profiles were analyzed,and the character of erosion and deposition under different tide conditions were illustrated.The net sand volume changes were got smaller under the spring tide condition rather than middle tide and neap tide conditions.Further study of the distribution of wave induced current at different stages of collision,inundation and ebb shown that the stronger current under spring tide condition would increase the sediment transport rate and reduce the deposition volume at profiles S3 and S6~S8,and the total amount of sediment involved in transportation had increased for the whole beach,leading to the reduction of net erosion volume at profiles S1,S2,S4 and S5.
文摘本文对海洋气象漂流观测仪实测、CMA最佳路径数据集、第5代全球气象再分析产品(ERA5)、交叉检验多平台融合矢量风场(CCMP)四种资料的海面风在超强台风“利奇马”期间的变化特征进行分析。ERA5、CCMP两种分析/再分析风资料与实测风的对比分析表明:(1)风速:当风力<10级时,漂流观测仪轨迹上的ERA5、CCMP风速较漂流观测仪实测风速偏小;将漂流观测仪实测风速订正到10 m高度,风力≤5级时偏差(Bias)绝对值最小,ERA5(CCMP)为4.3 m s^(-1)(4.6 m s^(-1)),风力为7~9级时Bias绝对值最大,约9.2~10.2 m s^(-1);“利奇马”近中心海域ERA5、CCMP最大风速较CMA最佳路径数据集偏小,ERA5(CCMP)偏小约10.7 m s^(-1)(4.6 m s^(-1));ERA5(CCMP)最大风速极值较CMA最佳路径数据集偏低54.5%(12.7%)。(2)风向:ERA5、CCMP与漂流观测仪实测风向相关系数接近于0;风力≤5级时风向较实测偏右,风力>5级时偏左。(3)ERA5、CCMP风向、风速在“利奇马”近中心海域偏差明显,远离中心海域二者吻合度较高。通过对ERA5、CCMP资料进一步分析发现:CCMP能清楚描述热带气旋风场结构及演变过程,“利奇马”为超强台风时结构参数η=Vr/Vmax分布上有闭合环状结构,表明该区域有环状大风速带;“利奇马”强迫时间T_f分布于移动路径两侧,ERA5(CCMP)最大强迫时间为45 h(54 h)。
