This paper presents a study on drag coefficients under typhoon wind forcing based on observations and numerical experiments. The friction velocity and wind speed are measured at a marine observation platform in the So...This paper presents a study on drag coefficients under typhoon wind forcing based on observations and numerical experiments. The friction velocity and wind speed are measured at a marine observation platform in the South China Sea. Three typhoons: SOULIK(2013), TRAMI(2013) and FITOW(2013) are observed at a buoy station in the northeast sea area of Pingtan Island. A new parameterization is formulated for the wind drag coefficient as a function of wind speed. It is found that the drag coefficient(Cd) increases linearly with the slope of 0.083′10^(-3) for wind speed less than 24 m s^(-1). To investigate the drag coefficient under higher wind conditions, three numerical experiments are implemented for these three typhoons using SWAN wave model. The wind input data are objective reanalysis datasets, which are assimilated with many sources and provided every six hours with the resolution of 0.125?×0.125?. The numerical simulation results show a good agreement with wave observation data under typhoon wind forcing. The results indicate that the drag coefficient levels off with the linear slope of 0.012′10^(-3) for higher wind speeds(less than 34 m s^(-1)) and the new parameterization improvese the simulation accuracy compared with the Wu(1982) default used in SWAN.展开更多
As one of the most serious natural disasters,many typhoons affect southeastern China every year.Taking Shenzhen,a coastal city in southeast China as an example,we employed a Monte-Carlo simulation to generate a large ...As one of the most serious natural disasters,many typhoons affect southeastern China every year.Taking Shenzhen,a coastal city in southeast China as an example,we employed a Monte-Carlo simulation to generate a large number of virtual typhoons for wind hazard analysis.By analyzing 67-year historical typhoons data from 1949 to 2015 using the Best Track Dataset for Tropical Cyclones over the Western North Pacific recorded by the Shanghai Typhoon Institute,China Meteorological Administration(CMASTI),typhoon characteristic parameters were extracted and optimal statistical distributions established for the parameters in relation to Shenzhen.We employed the Monte-Carlo method to sample each distribution to generate the characteristic parameters of virtual typhoons.In addition,the Yah Meng(YM)wind field model was introduced,and the sensitivity of the YM model to several parameters discussed.Using the YM wind field model,extreme wind speeds were extracted from the virtual typhoons.The extreme wind speeds for different return periods were predicted and compared with the current structural code to provide improved wind load information for wind-resistant structural design.展开更多
This paper proposes a rain considered geophysical model function （GMF）, to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on r...This paper proposes a rain considered geophysical model function （GMF）, to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency （JMA）. The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section （NRCS） is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective.展开更多
Altimetry data have been widely used in various fiehts of oceanography, including the extreme weather events such as tropical cyclones, typhoons, and hurricanes. The performance of JASON1 in Typhoon Shanshan is assess...Altimetry data have been widely used in various fiehts of oceanography, including the extreme weather events such as tropical cyclones, typhoons, and hurricanes. The performance of JASON1 in Typhoon Shanshan is assessed by examining the sensor geophysical data record and illustrates how the measured return waveform, significant wave height, and backscatter are all affected by various factors associated with the typhoon, with details by the rain are illustrated. The correction method to maintain accurate wave height and wind speed measurements in Typhoon Shanshan and the results are presented. Furthermore, the additional results of rain rate and typhoon eye diameter can be retrieved. Because of the lack of in-situ measurements of wind, wave, and rain rate at Typhoon Shanshan, results are compared with the forecasted typhoon data and a good agreement is found.展开更多
Leveraging the commercial CFD software FLUENT,the fine-scale three-dimensional wind structure over the Paiya Mountains on the Dapeng Peninsula near Shenzhen,a city on the seashore of South China Sea,during the landfal...Leveraging the commercial CFD software FLUENT,the fine-scale three-dimensional wind structure over the Paiya Mountains on the Dapeng Peninsula near Shenzhen,a city on the seashore of South China Sea,during the landfall of Typhoon Molave has been simulated and analyzed.Through the study,a conceptual wind structure model for mountainous areas under strong wind condition is established and the following conclusions are obtained as follows:(1)FLUENT can reasonably simulate a three-dimensional wind structure over mountainous areas under strong wind conditions;(2)the kinetic effect of a mountain can intensify wind speed in the windward side of the mountain and the area over the mountain peak;and(3)in the leeward side of the mountain,wind speed is relatively lower with relatively stronger wind shear and turbulence.展开更多
Diurnal wind （DW） and nonlinear interaction between inertial and tidal currents near the Xisha Islands of the South China Sea （SCS） during the passage of Typhoon Conson （2010） are investigated using observationa...Diurnal wind （DW） and nonlinear interaction between inertial and tidal currents near the Xisha Islands of the South China Sea （SCS） during the passage of Typhoon Conson （2010） are investigated using observational data and a damped slab model. It is found that the DWs, which are dominated by clockwise wind components, are prominent at our observational site. The DWs increase after the passage of the typhoon from 1 to about 4 m/s, which may be due to the decrease of the sea surface temperature caused by the passage of the typhoon. Kinetic energy spectra and bicoherence methods reveal nonlinear interactions between the inertial currents and the 2MK3 tidal constituent at our observational site. The slab damped model reproduces the inertial currents successfully induced by the total observed winds, and it is shown that the inertial currents induced by DWs are positively proportional to the DWs speed. Even though the observed inertial currents are distinct, the proportion of inertial currents induced by DWs to those induced by the total observed winds is just 0.7%/4% before/after the passage of typhoon. This shows that the inertial currents induced by the DWs are unimportant near the Xisha Islands during the typhoon season.展开更多
The Sutong Bridge, a cable-stayed located in the southeast coastal area of China, is vulnerable to the Pacific typhoons. From the data measured by two 3D ultrasonic anemometers at the height of 76 m and 306 m, the win...The Sutong Bridge, a cable-stayed located in the southeast coastal area of China, is vulnerable to the Pacific typhoons. From the data measured by two 3D ultrasonic anemometers at the height of 76 m and 306 m, the wind characteristics （including 10-minute mean wind speed and direction, turbulence intensity and gust factor, power spectral density and integral scale of turbulence） of Typhoon Kalmaegi are analyzed The comparison of 10-minute mean wind velocity from the two anemometers vali- dates the reliability of wind data. The turbulence intensities （Iu, Iv, and Iw） show the decreasing trend as the mean wind speed increases. The mean value of Iv/Iu is 0.94, while that of Iw/Iu is 0.90. Discrepancy exists between field-measured power spectra and code-suggested spectra. Those results can enlarge the wind database of the southeast coastal area of China, and provide references for wind resistance evaluation of the bridge.展开更多
Vertically exploring the characteristics of the typhoon boundary layer（TBL） plays an important role in recognizing typhoon structure. The boundary layer radial direction and tangential wind characteristics of Typhoo...Vertically exploring the characteristics of the typhoon boundary layer（TBL） plays an important role in recognizing typhoon structure. The boundary layer radial direction and tangential wind characteristics of Typhoon Usagi based on the observational data of three boundary layer wind profiler stations along the route of Typhoon Usagi（No. 1319） and by combining with sounding data. The results show that：（1） maximum tangential wind appears in the vicinity of the eye area of Usagi, and it basically maintains a height of around 1 800 m when Usagi keeps a strong typhoon level, with the rapidly decreasing strength of Usagi after it lands, the speed of the maximum tangential wind and its vertical range both decrease;（2） the height of the maximum tangential wind is close to that of the inflow layer top of the typhoon, and is greater than that of the boundary layer estimated on the basis of Richardson number or potential temperature gradient, while the height of mixed layer judged on the basis of the signal-to-noise ratio（SNR） or its gradient is usually low;（3） the the boundary layer height can reach higher than2 100 m before Usagi lands. When the typhoon level or above is achieved, the boundary layer height observed by various stations does not change much, basically staying at between 1 200 and 1 600 m. With the decreasing strength of Usagi after its landfall, the boundary layer height rapidly drops.展开更多
Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds...Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.展开更多
As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed,...As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed, direction and friction are introduced in this study to construct the asymmetric strengthening of the QuikSCAT wind field. Then by adopting a technology of four-dimensional data assimilation, an experiment that includes both the assimilation and forecasting phases is designed to simulate Typhoon Rananim numerically. The results show that with model constraints and adjustment, this technology can incorporate the QuikSCAT wind data to the entire column of the model atmosphere, improve greatly the simulating effects of the whole-column wind, pressure field and the track as well as the simulated typhoon intensity covered by the forecast phase, and work positively for the forecasting of landfall locations.展开更多
[Objective] The research aimed to study the wind vector structure variation of No.1013 strong typhoon 'catfish',and its influence on typhoon pathway mutation.[Method] According to the theory that the asymmetri...[Objective] The research aimed to study the wind vector structure variation of No.1013 strong typhoon 'catfish',and its influence on typhoon pathway mutation.[Method] According to the theory that the asymmetric structure of typhoon vortex had influence on typhoon movement,the center of No.1013 super typhoon 'catfish' was as the coordinate origin,and 850,500 hPa tangential rotation speeds within 300-500 km were decomposed into u and v components.The composite force movement tendency of typhoon was analyzed.The wind vector structure variation of No.1013 strong typhoon 'catfish' and its influence on typhoon pathway mutation were discussed.[Result] At the quick movement stage of No.1013 strong typhoon,the wind vector had obvious asymmetric structure.When the typhoon rotated in situ,the wind vector presented symmetric structure.When ΔU,ΔV and composite wind vector had obvious variations,the composite force of typhoon changed,and the moved direction also would change.The asymmetric structure of wind speed near 300-500 km around 500 and 850 hPa typhoon centers was favorable for tendency of moved pathway.The pointed directions of ΔU,ΔV and composite wind vector could be as the direction of composite force movement of typhoon.[Conclusion] The research provided reference basis for typhoon prevention.展开更多
Based on conventional meteorological observation data, NCEP 1° × 1° reanalysis data, reanalysis data with resolution 0.75° × 0.75° from ECMWF and Doppler weather radar, we analyzed the we...Based on conventional meteorological observation data, NCEP 1° × 1° reanalysis data, reanalysis data with resolution 0.75° × 0.75° from ECMWF and Doppler weather radar, we analyzed the weather conditions and physical characteristics of Super Typhoon Rammasun (1409), which caused special strong wind and severe rainstorm in Guangxi. The results show that: 1) Typhoon Rammasun offshore sudden strengthening in one of the main reasons was that loop pressure ridge superimposed into the westward extension of subtropical high, to making enable rapid strengthening of the subtropical high, so the subtropical high advanced faster than the Rammasun move, Rammasun center of the subtropical high distance reduced and the gradient increased;2) Rammasun northward to south china coast with plenty of vapor following ITCZ, before landing, southwest monsoon and cross-equatorial flow were involved, Rammasun got latent heat of monsoon jet, enabling it to strengthen in offshore;3) Rammasun from the Qiongzhou Strait into the northern Gulf, therefore the Strait of short passages and both sides belong to the low zone, friction consumption smaller, that was the main reason what was able to maintain the strength of the super typhoon, when Rammasun into the Beibu Gulf;4) Diagnostic analysis shows that Rammasun before entering the northern Gulf and into the Beibu Gulf later, vorticity weakened, divergence and vapor flux divergence changed were smaller, meanwhile, vertical ascent speed and latent heat transport both increased, which was important reason of severe rainstorm caused by Rammasun.展开更多
In this paper, we first analyzed cloud drift wind(CDW) data distribution in the vertical direction, and then reassigned the height of every CDW in the research domain in terms of background information, and finally, c...In this paper, we first analyzed cloud drift wind(CDW) data distribution in the vertical direction, and then reassigned the height of every CDW in the research domain in terms of background information, and finally, conducted contrast numerical experiments of assimilating the CDW data before and after reassignment to examine the impacts on the forecast of the track of Typhoon Chanthu(1003) from 00:00(Coordinated Universal Time) 21 July to 00:00 UTC23 July, 2010. The analysis results of the CDW data indicate that the number of CDWs is mainly distributed in the midand upper-troposphere above 500 h Pa, with the maximum number at about 300 h Pa. The height reassigning method mentioned in this work may update the height effectively, and the CDW data are distributed reasonably and no obvious contradiction occurs in the horizontal direction after height reassignment. After assimilating the height-reassigned CDW data, especially the water vapor CDW data, the initial wind field around Typhoon Chanthu(1003) became more reasonable, and then the steering current leading the typhoon to move to the correct location became stronger. As a result, the numerical track predictions are improved.展开更多
In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN （Simulating WAves Nearshore） model. T...In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN （Simulating WAves Nearshore） model. The three experiments adopt the Komen, Janssens, and Westhuysen expressions for wind input and whitecapping dissipation, respectively. Besides the above-mentioned source tems, other parameterization schemes in these experiments are the same. It shows that the experiment with the Westhuysen expression result in the least simulation errors while that with the Janssens expression has the most. The results from the experiments with Komen and Westhuysen expressions show that the differenees in significant wave height （SWH） have a good correlation with the differences in dissipation energy caused by whiteeapping. This indicates that the whitecapping dissipation source term plays an important role in the resultant differences of the simulated SWH between the two experiments.展开更多
基金supported by the National Natural Science Foundation of China(Nos.41276015,51509226)the Fundamental Research Funds for the Central Universities(No.201513040)Open Science Foundation of Key Laboratory of Digital Ocean,SOA(No.KLD0201404)
文摘This paper presents a study on drag coefficients under typhoon wind forcing based on observations and numerical experiments. The friction velocity and wind speed are measured at a marine observation platform in the South China Sea. Three typhoons: SOULIK(2013), TRAMI(2013) and FITOW(2013) are observed at a buoy station in the northeast sea area of Pingtan Island. A new parameterization is formulated for the wind drag coefficient as a function of wind speed. It is found that the drag coefficient(Cd) increases linearly with the slope of 0.083′10^(-3) for wind speed less than 24 m s^(-1). To investigate the drag coefficient under higher wind conditions, three numerical experiments are implemented for these three typhoons using SWAN wave model. The wind input data are objective reanalysis datasets, which are assimilated with many sources and provided every six hours with the resolution of 0.125?×0.125?. The numerical simulation results show a good agreement with wave observation data under typhoon wind forcing. The results indicate that the drag coefficient levels off with the linear slope of 0.012′10^(-3) for higher wind speeds(less than 34 m s^(-1)) and the new parameterization improvese the simulation accuracy compared with the Wu(1982) default used in SWAN.
基金Supported by the National Key Research and Development Program of China(Nos.2016YFC1402004,2016YFC1402000,2018YFC1407003)the National Natural Science Foundation of China(Nos.U1706216,U1606402,41421005)
文摘As one of the most serious natural disasters,many typhoons affect southeastern China every year.Taking Shenzhen,a coastal city in southeast China as an example,we employed a Monte-Carlo simulation to generate a large number of virtual typhoons for wind hazard analysis.By analyzing 67-year historical typhoons data from 1949 to 2015 using the Best Track Dataset for Tropical Cyclones over the Western North Pacific recorded by the Shanghai Typhoon Institute,China Meteorological Administration(CMASTI),typhoon characteristic parameters were extracted and optimal statistical distributions established for the parameters in relation to Shenzhen.We employed the Monte-Carlo method to sample each distribution to generate the characteristic parameters of virtual typhoons.In addition,the Yah Meng(YM)wind field model was introduced,and the sensitivity of the YM model to several parameters discussed.Using the YM wind field model,extreme wind speeds were extracted from the virtual typhoons.The extreme wind speeds for different return periods were predicted and compared with the current structural code to provide improved wind load information for wind-resistant structural design.
基金The National Natural Science Foundation of China under contract Nos 41005029,41105012 and 41105063the National Public Benefit (Meteorology) Research Foundation of China under contract No.GYHY201106004
文摘This paper proposes a rain considered geophysical model function （GMF）, to be noted as GMF plus Rain. GMF plus Rain is based on the basic raidative transfer model with attenuation and scattering effects of rain on radar signal considered. Combined with the NSCAT2 GMF and the rain correction model, the GMF plus Rain model is used to retrieve the ocean wind vectors from the collocated QuikSCAT and SSM/I rain rate data for typhoon Melor. The resulting wind speed estimates of typhoon Melor show improved agreement with the wind fields derived from the best track analysis of Japan Meteorological Agency （JMA）. The results imply that compared with the GMF model, the GMF plus Rain model can improve the precision of wind retrieval under the rain condition. Then, a new general algorithm of locating the eye of typhoon through the normalized radar cross section （NRCS） is proposed. The implementation of this algorithm in the ten QuikSCAT observations of typhoon Melor suggests that this algorithm is effective.
基金The National Natural Science Foundation of China under contract No. 30671619
文摘Altimetry data have been widely used in various fiehts of oceanography, including the extreme weather events such as tropical cyclones, typhoons, and hurricanes. The performance of JASON1 in Typhoon Shanshan is assessed by examining the sensor geophysical data record and illustrates how the measured return waveform, significant wave height, and backscatter are all affected by various factors associated with the typhoon, with details by the rain are illustrated. The correction method to maintain accurate wave height and wind speed measurements in Typhoon Shanshan and the results are presented. Furthermore, the additional results of rain rate and typhoon eye diameter can be retrieved. Because of the lack of in-situ measurements of wind, wave, and rain rate at Typhoon Shanshan, results are compared with the forecasted typhoon data and a good agreement is found.
基金National Natural Science Foundation of China(91215302,51278308)Open Project for State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics(LAPC)
文摘Leveraging the commercial CFD software FLUENT,the fine-scale three-dimensional wind structure over the Paiya Mountains on the Dapeng Peninsula near Shenzhen,a city on the seashore of South China Sea,during the landfall of Typhoon Molave has been simulated and analyzed.Through the study,a conceptual wind structure model for mountainous areas under strong wind condition is established and the following conclusions are obtained as follows:(1)FLUENT can reasonably simulate a three-dimensional wind structure over mountainous areas under strong wind conditions;(2)the kinetic effect of a mountain can intensify wind speed in the windward side of the mountain and the area over the mountain peak;and(3)in the leeward side of the mountain,wind speed is relatively lower with relatively stronger wind shear and turbulence.
基金The Knowledge Innovation Program of the Chinese Academy of Sciences under contract No.SQ201206the Innovation Group Program of State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences,under contract No.LTOZZ1201+1 种基金the National Basic Research Program under contract No.2013CB956101the National Natural Science Foundation of China under contract No.41025019
文摘Diurnal wind （DW） and nonlinear interaction between inertial and tidal currents near the Xisha Islands of the South China Sea （SCS） during the passage of Typhoon Conson （2010） are investigated using observational data and a damped slab model. It is found that the DWs, which are dominated by clockwise wind components, are prominent at our observational site. The DWs increase after the passage of the typhoon from 1 to about 4 m/s, which may be due to the decrease of the sea surface temperature caused by the passage of the typhoon. Kinetic energy spectra and bicoherence methods reveal nonlinear interactions between the inertial currents and the 2MK3 tidal constituent at our observational site. The slab damped model reproduces the inertial currents successfully induced by the total observed winds, and it is shown that the inertial currents induced by DWs are positively proportional to the DWs speed. Even though the observed inertial currents are distinct, the proportion of inertial currents induced by DWs to those induced by the total observed winds is just 0.7%/4% before/after the passage of typhoon. This shows that the inertial currents induced by the DWs are unimportant near the Xisha Islands during the typhoon season.
基金Supported by the Key Project of the National Natural Science Foundation of China (0538020)the National Natural Science Foundation of China for Distinguished Young Scientists (50725828)+1 种基金the National Natural Science Foundation of China (50908046)the Specialized Research Fund for the Doctoral Program of Higher Education (200802861012)
文摘The Sutong Bridge, a cable-stayed located in the southeast coastal area of China, is vulnerable to the Pacific typhoons. From the data measured by two 3D ultrasonic anemometers at the height of 76 m and 306 m, the wind characteristics （including 10-minute mean wind speed and direction, turbulence intensity and gust factor, power spectral density and integral scale of turbulence） of Typhoon Kalmaegi are analyzed The comparison of 10-minute mean wind velocity from the two anemometers vali- dates the reliability of wind data. The turbulence intensities （Iu, Iv, and Iw） show the decreasing trend as the mean wind speed increases. The mean value of Iv/Iu is 0.94, while that of Iw/Iu is 0.90. Discrepancy exists between field-measured power spectra and code-suggested spectra. Those results can enlarge the wind database of the southeast coastal area of China, and provide references for wind resistance evaluation of the bridge.
基金The National Natural Science Foundation of China under contract Nos 41305029 and 41475014the Science and Technology Planning Project of Guangdong Province of China under contract No.2013B020200013+1 种基金the Guangzhou Municipal Science and Technology Planning Project of China under contract No.201604020069the Meteorological Key Technology Integration and Application Projects of China Meteorological Administration under contract No.CMAGJ2015M42
文摘Vertically exploring the characteristics of the typhoon boundary layer（TBL） plays an important role in recognizing typhoon structure. The boundary layer radial direction and tangential wind characteristics of Typhoon Usagi based on the observational data of three boundary layer wind profiler stations along the route of Typhoon Usagi（No. 1319） and by combining with sounding data. The results show that：（1） maximum tangential wind appears in the vicinity of the eye area of Usagi, and it basically maintains a height of around 1 800 m when Usagi keeps a strong typhoon level, with the rapidly decreasing strength of Usagi after it lands, the speed of the maximum tangential wind and its vertical range both decrease;（2） the height of the maximum tangential wind is close to that of the inflow layer top of the typhoon, and is greater than that of the boundary layer estimated on the basis of Richardson number or potential temperature gradient, while the height of mixed layer judged on the basis of the signal-to-noise ratio（SNR） or its gradient is usually low;（3） the the boundary layer height can reach higher than2 100 m before Usagi lands. When the typhoon level or above is achieved, the boundary layer height observed by various stations does not change much, basically staying at between 1 200 and 1 600 m. With the decreasing strength of Usagi after its landfall, the boundary layer height rapidly drops.
基金Projects(51378396,51678452,51708074,2014M560706)supported by General Program of National Natural Science Foundation of ChinaProject(2014M560706)supported by the China Postdoctoral Science Foundation
文摘Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.
基金National Key Fundamental Research and Development Plan of China (2004CB418301)Natural Science Foundation of China (40830958)
文摘As an approach to the technological problem that the wind data of QuikSCAT scatterometer cannot accurately describe the zone of typhoon-level strong wind speed, some objective factors such as the typhoon moving speed, direction and friction are introduced in this study to construct the asymmetric strengthening of the QuikSCAT wind field. Then by adopting a technology of four-dimensional data assimilation, an experiment that includes both the assimilation and forecasting phases is designed to simulate Typhoon Rananim numerically. The results show that with model constraints and adjustment, this technology can incorporate the QuikSCAT wind data to the entire column of the model atmosphere, improve greatly the simulating effects of the whole-column wind, pressure field and the track as well as the simulated typhoon intensity covered by the forecast phase, and work positively for the forecasting of landfall locations.
文摘[Objective] The research aimed to study the wind vector structure variation of No.1013 strong typhoon 'catfish',and its influence on typhoon pathway mutation.[Method] According to the theory that the asymmetric structure of typhoon vortex had influence on typhoon movement,the center of No.1013 super typhoon 'catfish' was as the coordinate origin,and 850,500 hPa tangential rotation speeds within 300-500 km were decomposed into u and v components.The composite force movement tendency of typhoon was analyzed.The wind vector structure variation of No.1013 strong typhoon 'catfish' and its influence on typhoon pathway mutation were discussed.[Result] At the quick movement stage of No.1013 strong typhoon,the wind vector had obvious asymmetric structure.When the typhoon rotated in situ,the wind vector presented symmetric structure.When ΔU,ΔV and composite wind vector had obvious variations,the composite force of typhoon changed,and the moved direction also would change.The asymmetric structure of wind speed near 300-500 km around 500 and 850 hPa typhoon centers was favorable for tendency of moved pathway.The pointed directions of ΔU,ΔV and composite wind vector could be as the direction of composite force movement of typhoon.[Conclusion] The research provided reference basis for typhoon prevention.
文摘Based on conventional meteorological observation data, NCEP 1° × 1° reanalysis data, reanalysis data with resolution 0.75° × 0.75° from ECMWF and Doppler weather radar, we analyzed the weather conditions and physical characteristics of Super Typhoon Rammasun (1409), which caused special strong wind and severe rainstorm in Guangxi. The results show that: 1) Typhoon Rammasun offshore sudden strengthening in one of the main reasons was that loop pressure ridge superimposed into the westward extension of subtropical high, to making enable rapid strengthening of the subtropical high, so the subtropical high advanced faster than the Rammasun move, Rammasun center of the subtropical high distance reduced and the gradient increased;2) Rammasun northward to south china coast with plenty of vapor following ITCZ, before landing, southwest monsoon and cross-equatorial flow were involved, Rammasun got latent heat of monsoon jet, enabling it to strengthen in offshore;3) Rammasun from the Qiongzhou Strait into the northern Gulf, therefore the Strait of short passages and both sides belong to the low zone, friction consumption smaller, that was the main reason what was able to maintain the strength of the super typhoon, when Rammasun into the Beibu Gulf;4) Diagnostic analysis shows that Rammasun before entering the northern Gulf and into the Beibu Gulf later, vorticity weakened, divergence and vapor flux divergence changed were smaller, meanwhile, vertical ascent speed and latent heat transport both increased, which was important reason of severe rainstorm caused by Rammasun.
基金Specialized Science Project for Public Welfare Industries(Metrological Sector)(GYHY201206010,GYHY201406009)Science and Technology Planning Project for Guangdong Province(2012A061400012)+3 种基金Program for the 12th Five-Year Economic Development(2012BAC22B00)Natural Science Foundation of China(41075083)Program for Integration and Application of Key Meteorological Techniques from CMA(CMAGJ2012M36)Project from Guangdong Meteorological Bureau(2013A04)
文摘In this paper, we first analyzed cloud drift wind(CDW) data distribution in the vertical direction, and then reassigned the height of every CDW in the research domain in terms of background information, and finally, conducted contrast numerical experiments of assimilating the CDW data before and after reassignment to examine the impacts on the forecast of the track of Typhoon Chanthu(1003) from 00:00(Coordinated Universal Time) 21 July to 00:00 UTC23 July, 2010. The analysis results of the CDW data indicate that the number of CDWs is mainly distributed in the midand upper-troposphere above 500 h Pa, with the maximum number at about 300 h Pa. The height reassigning method mentioned in this work may update the height effectively, and the CDW data are distributed reasonably and no obvious contradiction occurs in the horizontal direction after height reassignment. After assimilating the height-reassigned CDW data, especially the water vapor CDW data, the initial wind field around Typhoon Chanthu(1003) became more reasonable, and then the steering current leading the typhoon to move to the correct location became stronger. As a result, the numerical track predictions are improved.
基金supported by the National Key Basic Research Project of China(Grant No.2007CB411805)the National Natural Science Foundation of China(Grant No.40675065)
文摘In order to investigate the effect of wind input and whitecapping dissipation on the simulation of typhoon-waves, three experiments are conducted with the latest version of SWAN （Simulating WAves Nearshore） model. The three experiments adopt the Komen, Janssens, and Westhuysen expressions for wind input and whitecapping dissipation, respectively. Besides the above-mentioned source tems, other parameterization schemes in these experiments are the same. It shows that the experiment with the Westhuysen expression result in the least simulation errors while that with the Janssens expression has the most. The results from the experiments with Komen and Westhuysen expressions show that the differenees in significant wave height （SWH） have a good correlation with the differences in dissipation energy caused by whiteeapping. This indicates that the whitecapping dissipation source term plays an important role in the resultant differences of the simulated SWH between the two experiments.
