In this study,the authors introduce a new bogus data assimilation method based on the dimension-reduced projection 4-DVar,which can resolve the cost function directly in low-dimensional space.The authors also try a ne...In this study,the authors introduce a new bogus data assimilation method based on the dimension-reduced projection 4-DVar,which can resolve the cost function directly in low-dimensional space.The authors also try a new method to improve the quality of samples,which are the base of dimension-reduced space projection bogus data assimilation (DRP-BDA).By running a number of numerical weather models with different model parameterization combinations on the typhoon Sinlaku,the authors obtained two groups of samples with different spreads and similarities.After DRP-BDA,the results show that,compared with the control runs,the simulated typhoon center pressure can be deepened by more than 20 hPa to 30 hPa and that the intensity can last as long as 60 hours.The mean track error is improved after DRP-BDA,and the structure of the typhoon is also improved.The wind near the typhoon center is enhanced dramatically,while the warm core is moderate.展开更多
A bogus typhoon scheme,designed for the initialization of a typhoon track prediction model,is developed in thispaper.This scheme includes both effects of axisymmetric wind and asymmetric wind.Experimental forecasts us...A bogus typhoon scheme,designed for the initialization of a typhoon track prediction model,is developed in thispaper.This scheme includes both effects of axisymmetric wind and asymmetric wind.Experimental forecasts using atwo-way interactive movable nested mesh model show that the forecast skill of typhoon tracks has clearly improvedafter introducing the bogus typhoon into the initial fields.展开更多
Critical functionality and huge infuence of the hot trend/topic page(HTP)in microblogging sites have driven the creation of a new kind of underground service called the bogus traffic service(BTS).BTS provides a kind o...Critical functionality and huge infuence of the hot trend/topic page(HTP)in microblogging sites have driven the creation of a new kind of underground service called the bogus traffic service(BTS).BTS provides a kind of illegal service which hijacks the HTP by pushing the controlled topics into it for malicious customers with the goal of guiding public opinions.To hijack HTP,the agents of BTS maintain an army of black-market accounts called bogus trafic accounts(BTAs)and control BTAs to generate a burst of fake trafic by massively retweeting the tweets containing the customer desired topic(hashtag).Although this service has been extensively exploited by malicious customers,little has been done to understand it.In this paper,we conduct a systematic measurement study of the BTS.We first investigate and collect 125 BTS agents from a variety of sources and set up a honey pot account to capture BTAs from these agents.We then build a BTA detector that detects 162218 BTAs from Weibo,the largest Chinese microblogging site,with a precision of 94.5%.We further use them as a bridge to uncover 296916 topics that might be involved in bogus trafic.Finally,we uncover the operating mechanism from the perspectives of the attack cycle and the attack entity.The highlights of our findings include the temporal attack patterns and intelligent evasion tactics of the BTAs.These findings bring BTS into the spotlight.Our work will help in understanding and ultimately eliminating this threat.展开更多
Observational and bogus satellite data are directly assimilated into the Weather Research and Forecast- ing （WRF） model in simulations of Typhoon Kalmaegi （2008）. The data assimilation is performed using the Radia...Observational and bogus satellite data are directly assimilated into the Weather Research and Forecast- ing （WRF） model in simulations of Typhoon Kalmaegi （2008）. The data assimilation is performed using the Radiative Transfer for TIROS-N Operational Vertical Sounder （RTTOV） model and the three-dimensional variational data assimilation （3DVAR） technique, with satellite observations taken from the National Oceanic and Atmospheric Administration-16 （NOAA-16） Advanced TIROS Vertical Sounder （ATOVS） system com- posed of the High-resolution Infrared Radiation Sounder （HIRS）, the Advanced Microwave Sounding Unit-A （AMSU-A）, and the Advanced Microwave Sounding Unit-B （AMSU-B）. Data assimilation experiments are initialized at three different times. Improvements in the numerical simulation of the typhoon are discussed in the context of wind, temperature, pressure, and geopotentiM fields. The results indicate that assimilation of satellite data can improve both the representation of the initial conditions and the subsequent simulation of the typhoon. Different satellite data have different impacts on the typhoon track. In these simulations, data from AMSU-A play a greater role in improving the simulation of the typhoon than data from AMSU-B or HIRS. Assimilation of satellite data significantly affects the sim- ulation of the subtropical high and the steering of the typhoon by the environmental flow. The subtropical high is enhanced and extends westward in the data assimilation experiments. The background flow therefore steers the typhoon more westward, improving the simulated typhoon track. Although direct assimilation of satellite brightness temperature improves the simulated environmental conditions, it does not significantly improve the simulated intensity of the typhoon. By contrast, initializing the typhoon simulation using bogus data in tandem with satellite data improves not only the environmental conditions but also the simulated inner-core structure of the typhoon. Assimilation of both types of data therefore improves the simulation of both the typhoon track and the typhoon intensity. The results of these experiments offer new insight into improving numerical simulations of typhoons.展开更多
Anti-misinformation groups emerge to patrol the micro-blogosphere As people across China mourned the tragic loss of life in the high-speed train crash on July 23 near Wenzhou, Zhejiang Province, Internet
以WRF(weather research forecasting)模式模拟了登陆后再入海0713号台风韦帕,同时考虑了中纬度过程不变与过程时变的各类SST海温场对模拟效果的作用。试验中重点分析热力影响因子[即模式的两种微物理方案LIN(Purdue Lin scheme)、WSM6(...以WRF(weather research forecasting)模式模拟了登陆后再入海0713号台风韦帕,同时考虑了中纬度过程不变与过程时变的各类SST海温场对模拟效果的作用。试验中重点分析热力影响因子[即模式的两种微物理方案LIN(Purdue Lin scheme)、WSM6(WRF single-moment 6-class scheme)]以及动力影响因子(即模式的台风BOGUS模型)对各类SST海温场的反应。分别并综合研究了热力、动力、及海温因子对再入海台风的路径及强度模拟所产生的影响。多项成组试验显示,台风过程时变的SST场的使用能够更好地诊断和模拟台风区海气相互作用并改善对再入海台风路径与强度的预测。对0713号台风模拟而言,微物理过程WSM6方案给出的结果(包括路径、气压、风力、以及感热和潜热等要素)比LIN方案更好。采用BOGUS模型对再入海台风的路径模拟有较明显改善。在台风再入海阶段,模拟的海气界面感热通量与潜热通量分布显示,正的感热通量高值区为台风生存提供能量,并对台风移动有较好的指示性;台风潜热通量高值区位于台风风力辐合增强区,此处潜热高值区与台风结构配合,对入海台风活动的持续有正贡献。而过程时变的SST场的使用对台风预测是有利的,其中6h时变的SST较日平均SST效果更显著。展开更多
The MM5 and its four dimensional variational data assimilation (4D-Var) system are used in this paper. Based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re...The MM5 and its four dimensional variational data assimilation (4D-Var) system are used in this paper. Based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, the authors generate an optimal initial condition for a typhoon by using the bogus data assimilation (BDA) scheme. BDA is able to recover many of the structural features of typhoons including a warm-core vertex, the correct center position, and the strong circulation. As a result of BDA using a bogus surface low, dramatic improvement is achieved in the 72 h prediction of typhoon Herb. Through several cases, the initialization by BDA effectively generates the harmonious inner structure of the typhoon, but which is lacking in the original analysis field. Therefore the intensity forecast is improved greatly. Some improvements are made in the track forecast, but more work still needs to be done.展开更多
The formation and development of typhoons are closely related to the disturbed low vortexes at the planetary boundary layer(PBL). The effects of five PBL parameterization schemes(PBL schemes hereinafter) on the trajec...The formation and development of typhoons are closely related to the disturbed low vortexes at the planetary boundary layer(PBL). The effects of five PBL parameterization schemes(PBL schemes hereinafter) on the trajectory,intensity, and distribution of physical quantities are studied using the mesoscale WRF model on Super Typhoon Sanba(2012) during its initial stage. Results show that the five PBL schemes exhibit significant different effects on the simulated intensity and path. The results simulated by QNSE and ACM2 without the Bogus method are close to the best track data in the numerical experiments. When the Bogus method is adopted, the simulated trajectories improve significantly because the initial field is close to the true data. Among the five PBL schemes, QNSE and ACM2 with the Bogus method present improved simulated path and intensity compared with the three other schemes. This finding indicates that the two schemes deal with the initial PBL process satisfactorily, especially in the formation and development of disturbed low vortexes. The differences in the treatment methods of the five PBL schemes affect the surface layer physical quantities and the middle and upper atmospheres during the middle to late periods of the typhoon.Although QNSE and ACM2 present better simulation results than other schemes, they exhibit a few differences in the internal structure of the typhoon. The results simulated by MYJ are worse, and this method may be unsuitable for studying the formation and development of typhoons.展开更多
基金the Ministry of Finance of China and the China Meteorological Administration for the Special Project of Meteorological Sector (Grant No. GYHY(QX)200906009)the National Natural Science Foundation of China for the innovation group project (Grant No.40821092)
文摘In this study,the authors introduce a new bogus data assimilation method based on the dimension-reduced projection 4-DVar,which can resolve the cost function directly in low-dimensional space.The authors also try a new method to improve the quality of samples,which are the base of dimension-reduced space projection bogus data assimilation (DRP-BDA).By running a number of numerical weather models with different model parameterization combinations on the typhoon Sinlaku,the authors obtained two groups of samples with different spreads and similarities.After DRP-BDA,the results show that,compared with the control runs,the simulated typhoon center pressure can be deepened by more than 20 hPa to 30 hPa and that the intensity can last as long as 60 hours.The mean track error is improved after DRP-BDA,and the structure of the typhoon is also improved.The wind near the typhoon center is enhanced dramatically,while the warm core is moderate.
文摘A bogus typhoon scheme,designed for the initialization of a typhoon track prediction model,is developed in thispaper.This scheme includes both effects of axisymmetric wind and asymmetric wind.Experimental forecasts using atwo-way interactive movable nested mesh model show that the forecast skill of typhoon tracks has clearly improvedafter introducing the bogus typhoon into the initial fields.
文摘Critical functionality and huge infuence of the hot trend/topic page(HTP)in microblogging sites have driven the creation of a new kind of underground service called the bogus traffic service(BTS).BTS provides a kind of illegal service which hijacks the HTP by pushing the controlled topics into it for malicious customers with the goal of guiding public opinions.To hijack HTP,the agents of BTS maintain an army of black-market accounts called bogus trafic accounts(BTAs)and control BTAs to generate a burst of fake trafic by massively retweeting the tweets containing the customer desired topic(hashtag).Although this service has been extensively exploited by malicious customers,little has been done to understand it.In this paper,we conduct a systematic measurement study of the BTS.We first investigate and collect 125 BTS agents from a variety of sources and set up a honey pot account to capture BTAs from these agents.We then build a BTA detector that detects 162218 BTAs from Weibo,the largest Chinese microblogging site,with a precision of 94.5%.We further use them as a bridge to uncover 296916 topics that might be involved in bogus trafic.Finally,we uncover the operating mechanism from the perspectives of the attack cycle and the attack entity.The highlights of our findings include the temporal attack patterns and intelligent evasion tactics of the BTAs.These findings bring BTS into the spotlight.Our work will help in understanding and ultimately eliminating this threat.
基金Supported by the International Scientific and Technological Cooperation Projects(2010DFA24650)National High-Tech Research and Development(863)Program of China(2010AA012304)+1 种基金China Meteorological Administration Special Public Welfare Research Fund(GYHY201106004)National Natural Science Foundation of China(41230421,41105065,and11271195)
文摘Observational and bogus satellite data are directly assimilated into the Weather Research and Forecast- ing （WRF） model in simulations of Typhoon Kalmaegi （2008）. The data assimilation is performed using the Radiative Transfer for TIROS-N Operational Vertical Sounder （RTTOV） model and the three-dimensional variational data assimilation （3DVAR） technique, with satellite observations taken from the National Oceanic and Atmospheric Administration-16 （NOAA-16） Advanced TIROS Vertical Sounder （ATOVS） system com- posed of the High-resolution Infrared Radiation Sounder （HIRS）, the Advanced Microwave Sounding Unit-A （AMSU-A）, and the Advanced Microwave Sounding Unit-B （AMSU-B）. Data assimilation experiments are initialized at three different times. Improvements in the numerical simulation of the typhoon are discussed in the context of wind, temperature, pressure, and geopotentiM fields. The results indicate that assimilation of satellite data can improve both the representation of the initial conditions and the subsequent simulation of the typhoon. Different satellite data have different impacts on the typhoon track. In these simulations, data from AMSU-A play a greater role in improving the simulation of the typhoon than data from AMSU-B or HIRS. Assimilation of satellite data significantly affects the sim- ulation of the subtropical high and the steering of the typhoon by the environmental flow. The subtropical high is enhanced and extends westward in the data assimilation experiments. The background flow therefore steers the typhoon more westward, improving the simulated typhoon track. Although direct assimilation of satellite brightness temperature improves the simulated environmental conditions, it does not significantly improve the simulated intensity of the typhoon. By contrast, initializing the typhoon simulation using bogus data in tandem with satellite data improves not only the environmental conditions but also the simulated inner-core structure of the typhoon. Assimilation of both types of data therefore improves the simulation of both the typhoon track and the typhoon intensity. The results of these experiments offer new insight into improving numerical simulations of typhoons.
文摘Anti-misinformation groups emerge to patrol the micro-blogosphere As people across China mourned the tragic loss of life in the high-speed train crash on July 23 near Wenzhou, Zhejiang Province, Internet
文摘以WRF(weather research forecasting)模式模拟了登陆后再入海0713号台风韦帕,同时考虑了中纬度过程不变与过程时变的各类SST海温场对模拟效果的作用。试验中重点分析热力影响因子[即模式的两种微物理方案LIN(Purdue Lin scheme)、WSM6(WRF single-moment 6-class scheme)]以及动力影响因子(即模式的台风BOGUS模型)对各类SST海温场的反应。分别并综合研究了热力、动力、及海温因子对再入海台风的路径及强度模拟所产生的影响。多项成组试验显示,台风过程时变的SST场的使用能够更好地诊断和模拟台风区海气相互作用并改善对再入海台风路径与强度的预测。对0713号台风模拟而言,微物理过程WSM6方案给出的结果(包括路径、气压、风力、以及感热和潜热等要素)比LIN方案更好。采用BOGUS模型对再入海台风的路径模拟有较明显改善。在台风再入海阶段,模拟的海气界面感热通量与潜热通量分布显示,正的感热通量高值区为台风生存提供能量,并对台风移动有较好的指示性;台风潜热通量高值区位于台风风力辐合增强区,此处潜热高值区与台风结构配合,对入海台风活动的持续有正贡献。而过程时变的SST场的使用对台风预测是有利的,其中6h时变的SST较日平均SST效果更显著。
文摘The MM5 and its four dimensional variational data assimilation (4D-Var) system are used in this paper. Based on the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, the authors generate an optimal initial condition for a typhoon by using the bogus data assimilation (BDA) scheme. BDA is able to recover many of the structural features of typhoons including a warm-core vertex, the correct center position, and the strong circulation. As a result of BDA using a bogus surface low, dramatic improvement is achieved in the 72 h prediction of typhoon Herb. Through several cases, the initialization by BDA effectively generates the harmonious inner structure of the typhoon, but which is lacking in the original analysis field. Therefore the intensity forecast is improved greatly. Some improvements are made in the track forecast, but more work still needs to be done.
基金National Natural Science Foundation of China(41375033,41225018)National Basic Research Program of China(973 Program)(2013CB430100)Fundamental Research Funds for Central Universities of Lanzhou University(LZUJBKY-2013-K16)
文摘The formation and development of typhoons are closely related to the disturbed low vortexes at the planetary boundary layer(PBL). The effects of five PBL parameterization schemes(PBL schemes hereinafter) on the trajectory,intensity, and distribution of physical quantities are studied using the mesoscale WRF model on Super Typhoon Sanba(2012) during its initial stage. Results show that the five PBL schemes exhibit significant different effects on the simulated intensity and path. The results simulated by QNSE and ACM2 without the Bogus method are close to the best track data in the numerical experiments. When the Bogus method is adopted, the simulated trajectories improve significantly because the initial field is close to the true data. Among the five PBL schemes, QNSE and ACM2 with the Bogus method present improved simulated path and intensity compared with the three other schemes. This finding indicates that the two schemes deal with the initial PBL process satisfactorily, especially in the formation and development of disturbed low vortexes. The differences in the treatment methods of the five PBL schemes affect the surface layer physical quantities and the middle and upper atmospheres during the middle to late periods of the typhoon.Although QNSE and ACM2 present better simulation results than other schemes, they exhibit a few differences in the internal structure of the typhoon. The results simulated by MYJ are worse, and this method may be unsuitable for studying the formation and development of typhoons.
