Evaporation duct is an abnormal refractive phenomenon in the marine atmosphere boundary layer. It has been generally accepted that the evaporation duct prominently affects the performance of the electronic equipment o...Evaporation duct is an abnormal refractive phenomenon in the marine atmosphere boundary layer. It has been generally accepted that the evaporation duct prominently affects the performance of the electronic equipment over the sea because of its wide distribution and frequent occurrence. It has become a research focus of the navies all over the world. At present, the diagnostic models of the evaporation duct are all based on the Monin-Obukhov similarity theory, with only differences in the flux and character scale calculations in the surface layer. These models are applicable to the stationary and uniform open sea areas without considering the alongshore effect. This paper introduces the nonlinear factor a and the gust wind item wg into the Babin model, and thus extends the evaporation duct diagnostic model to the offshore area under extremely low wind speed. In addition, an evaporation duct prediction model is designed and coupled with the fifth generation mesoscale model （MMS）. The tower observational data and radar data at the Pingtan island of Fujian Province on May 25-26, 2002 were used to validate the forecast results. The outputs of the prediction model agree with the observations from 0 to 48 h. The relative error of the predicted evaporation duct height is 19.3% and the prediction results are consistent with the radar detection.展开更多
A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics proc...A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics process, and by means of reducing the height of Yunnan-Guizhou Plateau and cutting off the middle-east of the Yunnan-Guizhou Plateau on the simulated tests, the question as how the ladder terrain on the west of Yunnan-Guizhou Plateau impact on the rainstorm of Guizhou was studied. The analysis results showed that the second ladder terrain of Yunnan-Guizhou Plateau only affected the development of convective clouds on its backward position,and hardly affected the rain on its upward. The whole terrain of the Yunnan-Guizhou Plateau had a distinct impact not only on the windward slope rainfall of the west of the plateau, but also on the rainfall distribution, intensity and continuing time of the convective clouds on the middle-east of the plateau.展开更多
In this study, singular vectors related to a heavy rainfall case over the Korean Peninsula were calculated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Mo...In this study, singular vectors related to a heavy rainfall case over the Korean Peninsula were calculated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model （MM5） adjoint modeling system. Tangent linear and adjoint models include moist physical processes, and a moist basic state and a moist total energy norm were used for the singular-vector calculations. The characteristics and nonlinear growth of the first singular vector were analyzed, focusing on the relationship between the basic state and the singular vector. The horizontal distribution of the initial singular vector was closely related to the baroclinicity index and the moisture availability of the basic state. The temperature-component energy at a lower level was dominant at the initial time, and the kinetic energy at upper levels became dominant at the final time in the energy profile of the singular vector. The nonlinear growth of the singular vector appropriately reflects the temporal variations in the basic state. The moisture-component energy at lower levels was dominant at earlier times, indicating continuous moisture transport in the basic state. There were a large amount of precipitation and corresponding latent heat release after that period because the continuous moisture transport created favorable conditions for both convective and nonconvective precipitation. The vertical propagation of the singular-vector energy was caused by precipitation and the corresponding latent heating in the basic state.展开更多
The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dim...The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dimensional variational data assimilation technology (4DVAR) can effectively assimilate all kinds of observed data, including rainfall data at the observed stations, so that the initial fields and the precipitation forecast can both be greatly improved. The non-hydrostatic meso-scale model (MM5) and its adjoint model are used to study the development of the mei-yu front rainstorm from 1200 UTC 25 June to 0600 UTC 26 June 1999. By numerical simulation experiments and assimilation experiments, the T106 data and the observed 6-hour rainfall data are assimilated. The influences of many factors, such as the choice of the assimilated variables and the weighting coefficient, on the precipitation forecast results are studied. The numerical results show that 4DVAR is valuable and important to mei-yu front rainfall prediction.展开更多
In this study,fog simulations were conducted using the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) in and around the Yodo River Basin,Japan.The purpose is to investigate the MM5 performance of fog simulatio...In this study,fog simulations were conducted using the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) in and around the Yodo River Basin,Japan.The purpose is to investigate the MM5 performance of fog simulation for long-term periods.The simulations were performed for January,February,March,and July,2005 with a coarse 3-kin and a nested fine 1-km grid domains. Results of the simulations were compared with data from ten meteorological observatories,fog sampling site in Mt.Rokko,and visibility measurem...展开更多
Using the NCEP reanalysis at 1“X“resolution in conjunction with satellite imagery,a studyis undertaken of easterly wave related rainstorm events on August 3~4,2001 in seaboards betweenno rthern Fujian and southern Z...Using the NCEP reanalysis at 1“X“resolution in conjunction with satellite imagery,a studyis undertaken of easterly wave related rainstorm events on August 3~4,2001 in seaboards betweenno rthern Fujian and southern Zhejiang,expounding the sc heme for computing helicity,and exploring therainstorm evolution and the genesis of the Yandang mountains-triggered a meso-vortex(Duan and Chen,2005)by means of helicity and Q vector diver gence.Be sides,MM5V2 is emplo yed to simulate the ea ster-ly wave caused me so-vwrtex.Results show that the development of the central intensity and location ofthe high-valued helicity is well indicative of the fallout area and the genesis of the me so-vortex,discove-ring that the space/time evolutio ns of helicity serve as indica tors of so me utility for the rainf all occur-rence;it is revealed that the calculated helicity is of higher precision than MM5V2 simulations in predic-ting the initial position and the track of the me so-vortex,wit h their combination contributing to the im-provement of predic ting the meso-vortex,al so,the space/time evolutions in the superimposition of thezone of largevalue helicity gradient s upon that of highr-value Q vector diver gence gradients can be used toaccurately foreca st the rainstorm happening and initial position of the me so-wrtex,thereby illustratingthe higher ability of dia gno sing the precipitation and it s system in the superimpose d re gion.展开更多
There is distinct difference in the tangential wind profile between different typhoons in the western North Pacific. At present, only two parameters, maximum wind and radius of maximum wind, are used in NCAR-AFWA bogu...There is distinct difference in the tangential wind profile between different typhoons in the western North Pacific. At present, only two parameters, maximum wind and radius of maximum wind, are used in NCAR-AFWA bogus for MM5 mesoscale numerical model. As a result, sometimes the outer structure of typhoon cannot be described accurately. The tangential wind profile of NCAR-AFWA bogus is improved by introducing radii of 25.7 m/s and 15.4 m/s, and then the track and intensity of Typhoon Nockten (No.0425) are simulated. The results show that the simulations of track and intensity of typhoon both have been improved by simultaneously introducing the radii in the tangential wind profile of typhoon bogus. At the same time, there is improvement in the gale wind range of the typhoon simulated.展开更多
In nested nonhydrostatic mesoscale model MM5,the characteristic quantities of atmospheric turbulence,i.e.,the standard deviations of the turbulent fluctuated speeds for three directions in PBL are computed by Mellor-Y...In nested nonhydrostatic mesoscale model MM5,the characteristic quantities of atmospheric turbulence,i.e.,the standard deviations of the turbulent fluctuated speeds for three directions in PBL are computed by Mellor-Yamada's level 2.5 closure scheme.The magnitudes and the vertical profiles of these quantities computed from the model are closely connected with temperature and wind speed profiles as well as the type of the ground with a significant diurnal variation,and are in agreement with known magnitudes and regularities in different stratification conditions.Hence the method in this paper is reasonable and convincible.Their horizontal distribution depends on the horizontal distribution of the stratification.The method of predicted characteristic quantities of turbulence from mesoscale model in this paper can be used in the problem of atmospheric diffusion and atmospheric environment.展开更多
Based on some advanced urban parameterization schemes for mesoscale model,a new urban canopy parameterization (UCP) for MM5 is developed.The UCP takes into account the impacts of urban infrastructure and anthropogenic...Based on some advanced urban parameterization schemes for mesoscale model,a new urban canopy parameterization (UCP) for MM5 is developed.The UCP takes into account the impacts of urban infrastructure and anthropogenic activity on the dynamic,thermal structures of urban surface layer and the urban surface energy budget in a more rational way according to conformation of MMS.The UCP is implemented in MM5 and validated by IOP data in 2001 winter BECAPEX and automatic meteorological station data in Beijing area.The results illustrate that UCP versus traditional urban parameterization in MM5,it can make MM5 reproduce main characteristics of winter UBL in Beijing,which include urban heat island and its diurnal evolvement,nocturnal elavated inversion in downtown area,and some dynamic stuctures such as TKE peak at the top of urban canopy,lower wind speed in urban surface layer and so on.展开更多
The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36 h from 0000 UTC 31 July to 1200 UTC 1 August 1996 were simulated by using the ...The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36 h from 0000 UTC 31 July to 1200 UTC 1 August 1996 were simulated by using the non-hydrostatic mesoscale model MM5. This period covered the process of typhoon HERB landfall at Taiwan and Fujian Provinces. Results show that the model successfully simulated the landfall process of typhoon HERB, revealed the most important characteristics of the mesoscale dynamic and thermodynamic and cloud-rain physical structure during its landfall. The simulated typhoon track was close to the observation. The center of cyclonic circulation simulated at 0000 UTC on 1 August 1996 (24 h integration) was located in shore near Fuqing, Fujian Province at which the typhoon was reported to landfall two hours later. It shows that strong upward motion formed by low level convergence existed in the eye-wall and subsidence at the eye. The wind field shows clear asymmetrical structure near the typhoon center. The cloud and rainband was screw-typed distributed around typhoon center, and consisted of meso-β scale rain cores. During the period of typhoon HERB staying near and passing over Taiwan, the lower cloud was developed in the eye region so that the previous clear typhoon eye on the satellite pictures became fuzzy. Observation shows that the typhoon center was 'warm', but the model simulations with higher space resolution show that in the mid-troposphere the region of eye-wall with stronger upward motion and more cloud-and rain- water was warmer than the eye. During the period of typhoon passing over Taiwan and its following landfall at Fujian, the track of model typhoon deviated about 30 km northward (i. e., rightward) because of the orographic effects of Taiwan Island, but the strength of the typhoon was not affected remarkably. The amount of rainfall on Taiwan in the 36 h simulations was enhanced more than six times by the orographic lifting of Taiwan Mountain.展开更多
A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An a...A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An air-sea model system （MM5 and Princeton Ocean Model（POM））was built to simulate meteorological dynamics and ocean circulation in the South China Sea（SCS）.In the POM the output of MM5 was used as the input data.With an increased number of vertical levels,a high-resolution planetary boundary layer scheme and updated landuse/vegetation data,the accuracy of computing wind,temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations.The simulated trajectory and wind speed of Utor are close to the observed results.The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta（PRD）area.At different meteorological stations in Hong Kong,the wind,temperature and sea surface pressure are well simulated.The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor,and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track.The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C.展开更多
The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show t...The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show that the numerical model can successfully simulatethe urban heat island effect and the wind and temperature fields which are affected by thecomplicated topography and urban heat island. The results show that: (1) the west area (from Haidianto Fengtai Districts) is always the high temperature center of Beijing, where the surfacetemperature is about 6 K higher than the other suburbs; and (2) due to the unique topography thewind of Beijing area during the daytime is southern anabatic wind and at the night is northernkatabatic wind. The results comparing well with the data from surface observation stations validatethe accuracy of the simulation.展开更多
By means of a three-dimensional meteorological model(MM5)and a chemical model,the distributions of tropospheric ozone and its precursors over China have been simulated in summer and winter time,16—18 August 1994 and ...By means of a three-dimensional meteorological model(MM5)and a chemical model,the distributions of tropospheric ozone and its precursors over China have been simulated in summer and winter time,16—18 August 1994 and 7—9 January 1995.The distribution of ozone over the Tibetan Plateau in summer time is deeply discussed.The simulated results indicate that the distributions of surface ozone and NO_x are in good agreement with observed results,and human activities and photochemical reactions are the main factors controlling the surface ozone and NO_x concentrations.In addition,higher ozone concentrations are coincided with the air convergence, and the lower concentrations are related to the air divergence.In summer,over the Tibetan Plateau the strong flow convergence results in higher ozone concentrations in the lower troposphere:and the strong flow divergence results in lower ozone concentrations in the upper troposphere.In winter time ozone concentrations show Iarge-scale characteristics controlled by westerly flow,and in the jet area they are lower than those outside the jet.展开更多
In this paper, two snowfall cases under different weather conditions in northern China are simulated by using the meso scale model MM5. Two-way nesting structure of domains is designed for each case. Among the explici...In this paper, two snowfall cases under different weather conditions in northern China are simulated by using the meso scale model MM5. Two-way nesting structure of domains is designed for each case. Among the explicit schemes of MM5, the Reisner graupel scheme is selected to describe the microphysical process. The simulated snow-bands of two cases are basically consistent with observations. The simulated results of microphysical processes are mainly discussed. The hydrometeors and their sources and sinks under different weather backgrounds are described. The feedback effects of microphysical processes on the thermal and dynamic processes are also discussed. Method that outputs the accumulative sources and sinks per hour is used to analyze the distribution characteristics of hydrometeors during the strongest snowfall period. Two sensitivity tests （called heat test and drag test） are conducted to examine the effects of microphysical processes on cloud produced by the latent heat and drag force. Results have shown that the distribution of particles has a close relation with temperature. The temperature of Beijing snowfall is under 0℃ and there exist vapor and solid phase particles, while Liaoning snowfall has vapor, liquid, and solid phase particles due to the warm temperature. The distribution of these particles is not the same at different development stages. From the analyses of the characteristics of sources and sinks, it is found that snow is mainly produced by the deposition and accretion with ice. Cloud water is crucial to graupel. The melting of ice-phase particles enhances the rain production. The results of heat tests and drag tests reveal that the microphysical processes have interacted with the dynamic and thermal processes. Latent heat release of hydrometeors feeds back positively on snowfall while the drag force not. At last, comparisons of simulated results have been done between the two different kinds of snowfall cases. The microphysical processes of Liaoning snowfall case is more complicated than those of Beijing snowfall case. The values of the cloud variables are larger and the interactions between the microphysical processes and the thermal and dynamic processes of Liaoning snowfall case are stronger than those of Beijing snowfall case.展开更多
The response of the South China Sea（SCS） to Typhoon Chanchu（2006） was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the ...The response of the South China Sea（SCS） to Typhoon Chanchu（2006） was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the velocity forcing was introduced in the eastern boundary and the computational schemes of heat fluxes at the surface were introduced. Comparison with the observation data shows that the simulated results are reliable. In the response process of the SCS to Typhoon Chanchu, the influence of the heat fluxes on thermal structure of the SCS was regionally different. Strong wind forcing would lead to upwelling phenomenon in the lateral boundary of deep water basin. Furthermore, the Ekman pumping theory was used to discuss subsurface upwelling and downwelling phenomenon in typhoon forced stage.展开更多
文摘Evaporation duct is an abnormal refractive phenomenon in the marine atmosphere boundary layer. It has been generally accepted that the evaporation duct prominently affects the performance of the electronic equipment over the sea because of its wide distribution and frequent occurrence. It has become a research focus of the navies all over the world. At present, the diagnostic models of the evaporation duct are all based on the Monin-Obukhov similarity theory, with only differences in the flux and character scale calculations in the surface layer. These models are applicable to the stationary and uniform open sea areas without considering the alongshore effect. This paper introduces the nonlinear factor a and the gust wind item wg into the Babin model, and thus extends the evaporation duct diagnostic model to the offshore area under extremely low wind speed. In addition, an evaporation duct prediction model is designed and coupled with the fifth generation mesoscale model （MMS）. The tower observational data and radar data at the Pingtan island of Fujian Province on May 25-26, 2002 were used to validate the forecast results. The outputs of the prediction model agree with the observations from 0 to 48 h. The relative error of the predicted evaporation duct height is 19.3% and the prediction results are consistent with the radar detection.
文摘A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics process, and by means of reducing the height of Yunnan-Guizhou Plateau and cutting off the middle-east of the Yunnan-Guizhou Plateau on the simulated tests, the question as how the ladder terrain on the west of Yunnan-Guizhou Plateau impact on the rainstorm of Guizhou was studied. The analysis results showed that the second ladder terrain of Yunnan-Guizhou Plateau only affected the development of convective clouds on its backward position,and hardly affected the rain on its upward. The whole terrain of the Yunnan-Guizhou Plateau had a distinct impact not only on the windward slope rainfall of the west of the plateau, but also on the rainfall distribution, intensity and continuing time of the convective clouds on the middle-east of the plateau.
基金funded by the Korea Meteorological Administration Research and Development Program (Grant No.RACS 2010-2016)supported by Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education,Science and Technology (MEST) (2010-00715)the Brain Korea 21Project
文摘In this study, singular vectors related to a heavy rainfall case over the Korean Peninsula were calculated using the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model （MM5） adjoint modeling system. Tangent linear and adjoint models include moist physical processes, and a moist basic state and a moist total energy norm were used for the singular-vector calculations. The characteristics and nonlinear growth of the first singular vector were analyzed, focusing on the relationship between the basic state and the singular vector. The horizontal distribution of the initial singular vector was closely related to the baroclinicity index and the moisture availability of the basic state. The temperature-component energy at a lower level was dominant at the initial time, and the kinetic energy at upper levels became dominant at the final time in the energy profile of the singular vector. The nonlinear growth of the singular vector appropriately reflects the temporal variations in the basic state. The moisture-component energy at lower levels was dominant at earlier times, indicating continuous moisture transport in the basic state. There were a large amount of precipitation and corresponding latent heat release after that period because the continuous moisture transport created favorable conditions for both convective and nonconvective precipitation. The vertical propagation of the singular-vector energy was caused by precipitation and the corresponding latent heating in the basic state.
基金This work was supported by the National Natural Science Foundation of China under Grant Nos.40105012,49928504,and 40221503“973”Project under Grant No.G1999032801the Key Innovation Direction Project of the Chinese Academy of Sciences under Grant No.KZCX2208.The authors warmly thank Wu Rongsheng and Wang Yuan of N anjing University for their valuable advice.
文摘The numerical forecasts of mei-yu front rainstorms in China has been an important issue. The intensity and pattern of the frontal rainfall are greatly influenced by the initial fields of the numerical model. The 4-dimensional variational data assimilation technology (4DVAR) can effectively assimilate all kinds of observed data, including rainfall data at the observed stations, so that the initial fields and the precipitation forecast can both be greatly improved. The non-hydrostatic meso-scale model (MM5) and its adjoint model are used to study the development of the mei-yu front rainstorm from 1200 UTC 25 June to 0600 UTC 26 June 1999. By numerical simulation experiments and assimilation experiments, the T106 data and the observed 6-hour rainfall data are assimilated. The influences of many factors, such as the choice of the assimilated variables and the weighting coefficient, on the precipitation forecast results are studied. The numerical results show that 4DVAR is valuable and important to mei-yu front rainfall prediction.
文摘In this study,fog simulations were conducted using the Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) in and around the Yodo River Basin,Japan.The purpose is to investigate the MM5 performance of fog simulation for long-term periods.The simulations were performed for January,February,March,and July,2005 with a coarse 3-kin and a nested fine 1-km grid domains. Results of the simulations were compared with data from ten meteorological observatories,fog sampling site in Mt.Rokko,and visibility measurem...
基金supported by the National Natural Science Foundation of China(40875025,40875030,40775033,40405009)
文摘Using the NCEP reanalysis at 1“X“resolution in conjunction with satellite imagery,a studyis undertaken of easterly wave related rainstorm events on August 3~4,2001 in seaboards betweenno rthern Fujian and southern Zhejiang,expounding the sc heme for computing helicity,and exploring therainstorm evolution and the genesis of the Yandang mountains-triggered a meso-vortex(Duan and Chen,2005)by means of helicity and Q vector diver gence.Be sides,MM5V2 is emplo yed to simulate the ea ster-ly wave caused me so-vwrtex.Results show that the development of the central intensity and location ofthe high-valued helicity is well indicative of the fallout area and the genesis of the me so-vortex,discove-ring that the space/time evolutio ns of helicity serve as indica tors of so me utility for the rainf all occur-rence;it is revealed that the calculated helicity is of higher precision than MM5V2 simulations in predic-ting the initial position and the track of the me so-vortex,wit h their combination contributing to the im-provement of predic ting the meso-vortex,al so,the space/time evolutions in the superimposition of thezone of largevalue helicity gradient s upon that of highr-value Q vector diver gence gradients can be used toaccurately foreca st the rainstorm happening and initial position of the me so-wrtex,thereby illustratingthe higher ability of dia gno sing the precipitation and it s system in the superimpose d re gion.
基金Experiments on coupling typhoons, waves and storm surges in the South China Sea andpreviews of typhoon-inflicted disasters, a project from the research foundation for the science of tropical andmarine meteorology
文摘There is distinct difference in the tangential wind profile between different typhoons in the western North Pacific. At present, only two parameters, maximum wind and radius of maximum wind, are used in NCAR-AFWA bogus for MM5 mesoscale numerical model. As a result, sometimes the outer structure of typhoon cannot be described accurately. The tangential wind profile of NCAR-AFWA bogus is improved by introducing radii of 25.7 m/s and 15.4 m/s, and then the track and intensity of Typhoon Nockten (No.0425) are simulated. The results show that the simulations of track and intensity of typhoon both have been improved by simultaneously introducing the radii in the tangential wind profile of typhoon bogus. At the same time, there is improvement in the gale wind range of the typhoon simulated.
基金This work was supported by National Natural Science Foundation of China under Grant No.49875005.
文摘In nested nonhydrostatic mesoscale model MM5,the characteristic quantities of atmospheric turbulence,i.e.,the standard deviations of the turbulent fluctuated speeds for three directions in PBL are computed by Mellor-Yamada's level 2.5 closure scheme.The magnitudes and the vertical profiles of these quantities computed from the model are closely connected with temperature and wind speed profiles as well as the type of the ground with a significant diurnal variation,and are in agreement with known magnitudes and regularities in different stratification conditions.Hence the method in this paper is reasonable and convincible.Their horizontal distribution depends on the horizontal distribution of the stratification.The method of predicted characteristic quantities of turbulence from mesoscale model in this paper can be used in the problem of atmospheric diffusion and atmospheric environment.
基金supported by the"Air,Water and Soil Environmental Pollution Mechanism and Its Regulating-Controlling Principles in Beijing and Its Ambient Areas"of the State Plan for Key Basic Research of China (No.G1999045700)
文摘Based on some advanced urban parameterization schemes for mesoscale model,a new urban canopy parameterization (UCP) for MM5 is developed.The UCP takes into account the impacts of urban infrastructure and anthropogenic activity on the dynamic,thermal structures of urban surface layer and the urban surface energy budget in a more rational way according to conformation of MMS.The UCP is implemented in MM5 and validated by IOP data in 2001 winter BECAPEX and automatic meteorological station data in Beijing area.The results illustrate that UCP versus traditional urban parameterization in MM5,it can make MM5 reproduce main characteristics of winter UBL in Beijing,which include urban heat island and its diurnal evolvement,nocturnal elavated inversion in downtown area,and some dynamic stuctures such as TKE peak at the top of urban canopy,lower wind speed in urban surface layer and so on.
基金Supported by the Program of "Research on the Formation MechanismPrediction Theory of Severe Synoptic Disasters in China" (G1998040907).
文摘The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36 h from 0000 UTC 31 July to 1200 UTC 1 August 1996 were simulated by using the non-hydrostatic mesoscale model MM5. This period covered the process of typhoon HERB landfall at Taiwan and Fujian Provinces. Results show that the model successfully simulated the landfall process of typhoon HERB, revealed the most important characteristics of the mesoscale dynamic and thermodynamic and cloud-rain physical structure during its landfall. The simulated typhoon track was close to the observation. The center of cyclonic circulation simulated at 0000 UTC on 1 August 1996 (24 h integration) was located in shore near Fuqing, Fujian Province at which the typhoon was reported to landfall two hours later. It shows that strong upward motion formed by low level convergence existed in the eye-wall and subsidence at the eye. The wind field shows clear asymmetrical structure near the typhoon center. The cloud and rainband was screw-typed distributed around typhoon center, and consisted of meso-β scale rain cores. During the period of typhoon HERB staying near and passing over Taiwan, the lower cloud was developed in the eye region so that the previous clear typhoon eye on the satellite pictures became fuzzy. Observation shows that the typhoon center was 'warm', but the model simulations with higher space resolution show that in the mid-troposphere the region of eye-wall with stronger upward motion and more cloud-and rain- water was warmer than the eye. During the period of typhoon passing over Taiwan and its following landfall at Fujian, the track of model typhoon deviated about 30 km northward (i. e., rightward) because of the orographic effects of Taiwan Island, but the strength of the typhoon was not affected remarkably. The amount of rainfall on Taiwan in the 36 h simulations was enhanced more than six times by the orographic lifting of Taiwan Mountain.
文摘A severe typhoon Utor,occurring between July 3 and 8,2001,brought heavy rainfall,strong wind and storm surge.Utor was responsible for tremendous destruction and economic losses in Philippines,Taiwan and Guangdong.An air-sea model system （MM5 and Princeton Ocean Model（POM））was built to simulate meteorological dynamics and ocean circulation in the South China Sea（SCS）.In the POM the output of MM5 was used as the input data.With an increased number of vertical levels,a high-resolution planetary boundary layer scheme and updated landuse/vegetation data,the accuracy of computing wind,temperature and other meteorological fields are improved in near surface and upper levels in MM5 simulations.The simulated trajectory and wind speed of Utor are close to the observed results.The simulated distribution of rainfall is accorded well with measured data in the Pearl River Delta（PRD）area.At different meteorological stations in Hong Kong,the wind,temperature and sea surface pressure are well simulated.The simulated ocean surface current and surface temperature fields have an obvious rightward-biased response to the typhoon Utor,and the maximum velocity and the lowest temperature region appear in the 30 km of the right side of the typhoon track.The typhoon Utor could make the water 50m under the surface ocean unwell to surface and the ocean surface temperature decrease by about 2°C.
基金Project supported by the National Natural Science Foundation of China and Hong Kong under Grant Nos. 40275004,4001161948.
文摘The non-hydrostatic mesoscale model MM5V3 is used to simulate the wind andtemperature fields of the atmospheric boundary layer over Beijing area in summer with the meshresolution of 1 km. The simulation results show that the numerical model can successfully simulatethe urban heat island effect and the wind and temperature fields which are affected by thecomplicated topography and urban heat island. The results show that: (1) the west area (from Haidianto Fengtai Districts) is always the high temperature center of Beijing, where the surfacetemperature is about 6 K higher than the other suburbs; and (2) due to the unique topography thewind of Beijing area during the daytime is southern anabatic wind and at the night is northernkatabatic wind. The results comparing well with the data from surface observation stations validatethe accuracy of the simulation.
基金National Natural Science Foundation of China under Grant 49392200.
文摘By means of a three-dimensional meteorological model(MM5)and a chemical model,the distributions of tropospheric ozone and its precursors over China have been simulated in summer and winter time,16—18 August 1994 and 7—9 January 1995.The distribution of ozone over the Tibetan Plateau in summer time is deeply discussed.The simulated results indicate that the distributions of surface ozone and NO_x are in good agreement with observed results,and human activities and photochemical reactions are the main factors controlling the surface ozone and NO_x concentrations.In addition,higher ozone concentrations are coincided with the air convergence, and the lower concentrations are related to the air divergence.In summer,over the Tibetan Plateau the strong flow convergence results in higher ozone concentrations in the lower troposphere:and the strong flow divergence results in lower ozone concentrations in the upper troposphere.In winter time ozone concentrations show Iarge-scale characteristics controlled by westerly flow,and in the jet area they are lower than those outside the jet.
基金Supported jointly by the Dedicated Research Fund for Public Interest from the Ministry of Science and Technology of China (2002DIA20013 and 2004DIB3J116)the National Natural Science Foundation of China under Grant No.40305001.
文摘In this paper, two snowfall cases under different weather conditions in northern China are simulated by using the meso scale model MM5. Two-way nesting structure of domains is designed for each case. Among the explicit schemes of MM5, the Reisner graupel scheme is selected to describe the microphysical process. The simulated snow-bands of two cases are basically consistent with observations. The simulated results of microphysical processes are mainly discussed. The hydrometeors and their sources and sinks under different weather backgrounds are described. The feedback effects of microphysical processes on the thermal and dynamic processes are also discussed. Method that outputs the accumulative sources and sinks per hour is used to analyze the distribution characteristics of hydrometeors during the strongest snowfall period. Two sensitivity tests （called heat test and drag test） are conducted to examine the effects of microphysical processes on cloud produced by the latent heat and drag force. Results have shown that the distribution of particles has a close relation with temperature. The temperature of Beijing snowfall is under 0℃ and there exist vapor and solid phase particles, while Liaoning snowfall has vapor, liquid, and solid phase particles due to the warm temperature. The distribution of these particles is not the same at different development stages. From the analyses of the characteristics of sources and sinks, it is found that snow is mainly produced by the deposition and accretion with ice. Cloud water is crucial to graupel. The melting of ice-phase particles enhances the rain production. The results of heat tests and drag tests reveal that the microphysical processes have interacted with the dynamic and thermal processes. Latent heat release of hydrometeors feeds back positively on snowfall while the drag force not. At last, comparisons of simulated results have been done between the two different kinds of snowfall cases. The microphysical processes of Liaoning snowfall case is more complicated than those of Beijing snowfall case. The values of the cloud variables are larger and the interactions between the microphysical processes and the thermal and dynamic processes of Liaoning snowfall case are stronger than those of Beijing snowfall case.
基金supported by the National Nature Science Foundation of China(Grant No.40906006)the Fundamental Research Funds for the Central Universities
文摘The response of the South China Sea（SCS） to Typhoon Chanchu（2006） was examined using the MM5 and POM model. In the POM model, sea surface boundary conditions were forced by the simulation wind field from MM5, the velocity forcing was introduced in the eastern boundary and the computational schemes of heat fluxes at the surface were introduced. Comparison with the observation data shows that the simulated results are reliable. In the response process of the SCS to Typhoon Chanchu, the influence of the heat fluxes on thermal structure of the SCS was regionally different. Strong wind forcing would lead to upwelling phenomenon in the lateral boundary of deep water basin. Furthermore, the Ekman pumping theory was used to discuss subsurface upwelling and downwelling phenomenon in typhoon forced stage.
