The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and w...The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are studied.The results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow fields.The lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.展开更多
With the definition of generalized potential temperature, a new generalized frontogenesis function, which is expressed as the Lagrangian change rate of the magnitude of the horizontal generalized potential temperature...With the definition of generalized potential temperature, a new generalized frontogenesis function, which is expressed as the Lagrangian change rate of the magnitude of the horizontal generalized potential temperature gradient, is derived. Such a frontogenesis function is more appropriate for a real moist atmosphere because it can reflect frontogenesis processes, in which the atmosphere in a frontal zone is typically characterized by neither completely dry nor uniform saturation. Furthermore, by derivation, the expression of generalized frontogenesis function includes both temperature and humidity gradients, which is different from and superior to the traditional frontogenesis function in moist processes, which also uses equivalent potential temperature. Diagnostic studies of real cases are performed and show that the generalized frontogenesis function in non- uniformly saturated moist atmosphere indeed provides a useful tool for frontogenesis, compared to using the traditional frontogenesis function. The new frontogenesis function can be used in situations involving either a strong temperature or moisture gradient and is closely correlated with precipitation.展开更多
A new frontogenesis function is developed and analyzed on the basis of a local change rate of the absolute horizontal gradient of the resultant deformation. Different from the traditional frontogenesis function, the n...A new frontogenesis function is developed and analyzed on the basis of a local change rate of the absolute horizontal gradient of the resultant deformation. Different from the traditional frontogenesis function, the newly defined deformation frontogenesis is derived from the viewpoint of dynamics rather than thermodynamics. Thus, it is more intuitive for the study of frontogenesis because the compaction of isolines of both temperature and moisture can be directly induced by the change of a flow field. This new frontogenesis function is particularly useful for studying the mei-yu front in China because mei-yu rainbands typically consist of a much stronger moisture gradient than temperature gradient, and involve large deformation flow. An analysis of real mei-yu frontal rainfall events indicates that the deformation frontogenesis function works remarkably well, producing a clearer mei-yu front than the traditional frontogenesis function based on a measure of the potential temperature gradient. More importantly, the deformation frontogenesis shows close correlation with the subsequent(6 h later) precipitation pattern and covers the rainband well, bearing significance for the prognosis or even prediction of future precipitation.展开更多
If the initial fields are not in geostrophic balance, the adjustment and evolution will occur in the stratified fluid. and the frontogenesis will occur under suitable conditions. The evolution is studied here with a n...If the initial fields are not in geostrophic balance, the adjustment and evolution will occur in the stratified fluid. and the frontogenesis will occur under suitable conditions. The evolution is studied here with a nonhydrostatic fully compressible meso-scale model (Advanced Regional Prediction System, ARPS). Four cases are designed and compared: (i) control experiment: (ii) with different initial temperature gradient; (iii) with vapor distribution; (iv) with orographic forcing. The results show that: (1) there is an inertial oscillation in the evolution of the imbalanced flow with the frequency of the local Coriolis f, and with its amplitude decreasing with time. The stationary balanced state can only be approached as it cannot be reached in the limit duration of time. The energy conversion ratio varies in the range of [0, 1; 3]; (2) the stronger initial temperature gradient can make the final energy conversion ratio higher. and vice versa; (3) suitable vapor distribution is favorable for the frontogenesis. It will bring forward the time of the frontogenesis, strengthen the intensity of the cold front, and influence the final energy conversion ratio; (4) the orographic forcing has an evidently strengthening effect on the frontogenesis. The strengthening effect on the frontogenesis and the influence on the final energy conversion ratio depend on the relative location of the mountain to the cold front.展开更多
Observational study shows that, in some cases, the frontal structure displays the features of gravitative flows. It seems that the formation of discontinuity is an important problem in the study of the frontogenesis w...Observational study shows that, in some cases, the frontal structure displays the features of gravitative flows. It seems that the formation of discontinuity is an important problem in the study of the frontogenesis which is usually defined as an increasing of the scalar gradient. In this paper, the characteristic features of air flow with initial imbalance between the wind and the density fields are studied. Much attention is paid on the condition for the formation of discontinuity and its time scale. It is found that the initial distribution of density plays an important role in the formation of the discontinuity which happens in short time duration.展开更多
The artificial compression method (ACM) that is generally used to capture the contact discontinuity in nonviscous flows is used here in the simulation of quasi-geostrophic ideal frontogenesis in two dimensions. A comp...The artificial compression method (ACM) that is generally used to capture the contact discontinuity in nonviscous flows is used here in the simulation of quasi-geostrophic ideal frontogenesis in two dimensions. A comparison is made among the result of the ACM, the simulation result of Cullen, and the exact solution of the semi-geostrophic equations. The simulated front in this paper is more prominent than Cullen′s and is much closer to the exact solution.展开更多
On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using t...On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using the thermodynamical equation and frontogenetical function. The results show that the outbreak of the severe storm is closely related to the local frontogenesis. In fact, the interaction between the shearing instability of the low-level jet (LLJ) and the topographic forcing generates an gravity-inertia wave as well as local frontogenesis (the ?rst front), which consequently induce the onset of the severe storm. From then on, owing to the horizontal and vertical advection of the potential temperature, the new frontogenesis (the second front) is formed to the northeast side of the severe storm, which initiates the second rain belt. Meanwhile, a two-front structure emerges over the southeastern part of Hubei province. Accompanied with the further intensi?cation of the convection, the rain droplets evaporation cooling strengthens the ?rst front and weakens the second front, resulting in single front structure over the southeastern part of Hubei province in the period of the strong convection.展开更多
Using the PSU/NCAR Mesoscale Model version four(MM4), the frontogenesis and geostrophic adjustment problem in atmosphere with imbalance initial ideal data and conditions are studied. Based on results of experiments,...Using the PSU/NCAR Mesoscale Model version four(MM4), the frontogenesis and geostrophic adjustment problem in atmosphere with imbalance initial ideal data and conditions are studied. Based on results of experiments, it is found that the objective analysis and initialization procedure of the Model are not sensitive to the initial conditions used in this study. The final state of atmosphere, through process of adjustment, depends on the temperature gradient intensity of initial imbalance conditions. The front can be formed with appropriate condition. The processes of the frontogenesis are studied. It is also found that the response of the model to the ideal initial data used in this investigation is sensitive to the selected lateral boundary condition. The time-dependent inflow/outflow lateral boundary condition is the best implemented option for this numerical study. Energetic study of the experiments shows that the front is formed after the initial transient stage when there is no exchange of energy between the kinetic and potential energy. The time needed for the formation of the front is longer than that predicted theoretically. The ratio of kinetic energy to the released potential energy is considered. This ratio varies with the temperature gradient intensity and the type of used wind for computing kinetic energy (geostrophic or geostrophic plus ageostrophic wind). The larger temperature gradient, the larger magnitude of this ratio. A maximum value of energy in either type of computed kinetic energies (geostrophic wind kinetic energy and actual wind kinetic energy) for cases that the fronts are observed whereby, and its magnitude and occurrence time depend on initial data distribution. The variation of the computed kinetic energies with time, after transition time, is reasonable and no significant conversion of the energy between kinetic and potential energy goes on, however, stability within variables is not achieved.展开更多
This paper diagnoses and analyses the developmental mechanism of a process of extratropical transition of a tropical cyclone which occurred over West Pacific Ocean based on a diagnosis method of potential vorticity in...This paper diagnoses and analyses the developmental mechanism of a process of extratropical transition of a tropical cyclone which occurred over West Pacific Ocean based on a diagnosis method of potential vorticity inversion of frontogenesis.The study diagnoses quantitatively the role and effect of dynamic influence of westerly cold troughs,middle-latitude baroclinic frontal zones,cyclone cycles and unbalanced wind fields during the different stages of the extratropical transition of a tropical cyclone,and also discusses the interaction between them and the developmental mechanism.The results show that there are different developmental mechanisms during each stage of the extratropical transition and the processes are also unbalanced.展开更多
A two-dimensional mesoscale model is used to investigate the effect of background wind field andcharacter of the underlying surface on the coastal frontogenesis along the east continental coast when cold air outbreak....A two-dimensional mesoscale model is used to investigate the effect of background wind field andcharacter of the underlying surface on the coastal frontogenesis along the east continental coast when cold air outbreak. The results of numerical experiments indicate that the coastal frontogenesis mainly appears near ground atnight. When the background wind is easterly, it is favorable to coastal frontogenesis in the lower layer of the atmosphere. When the background wind is westerly, it is unfavorable to coastal frontogenesis in the lower layer of theatmosphere. The vertical shear of the background wind has important influence on the coastal frontogenesis. Thecoastal frontogenesis at lower layer at night is strengthened with increasing temperature difference between sea andair. The effect of coastal sloping terrain on the coastal frontogenesis is little when the topography sloping angle islesser.The analysis of the physical mechanism of frontogenesis shows that the main factor influencing the coastalfrontogenesis is the deformation field of horizontal wind speed.展开更多
This paper improves Bannon's work on the quasi-geostrophic frontogenesis in a horizontal deformation field. By setting the lower boundary condition for the equation of potential temperature on the realistic topogr...This paper improves Bannon's work on the quasi-geostrophic frontogenesis in a horizontal deformation field. By setting the lower boundary condition for the equation of potential temperature on the realistic topography instead of on z = 0, a general solution for the temperature field is derived after applying conformal mapping to the equation for the potential temperature, the vertical velocity and divergence field are also calculated. The general characteristics for the frontogenetic process still are frontolytic for warm front and frontogenetic for cold front in downstream of a mountain and the reverse is true upstream of a mountain, but more fine spatial structure of the temperature field and frontogenetic characteristics than Bannon's are obtained near surface because of the treatment of lower boundary condition. It is concluded that the frontogenetic characteristics are related to the translating speed of the deformation field with respect to the topography.展开更多
A method of linear momentum approximation is proposed that deals with weak nonlinear problems in an approximate manner. A motion of nonlinear nature is obtained in the system by assuming the motion to be in the form o...A method of linear momentum approximation is proposed that deals with weak nonlinear problems in an approximate manner. A motion of nonlinear nature is obtained in the system by assuming the motion to be in the form of linear momentum flow in the corresponding space introduced, followed by the transformation from the specified into a physical space. Significant results have been thereby derived in examining the effects of baroclinic Ekman momentum flow upon Eady-type baroclinic waves and frontogenesis. Also, this technique can be applied to investigate the dynamic characteristics of the weak nonlinear boundary layer including topography, stratification and non-Ekmantype friction for gaining further insight into the influence on the boundary layer inner parameters of terrain, baroclinicity and inhomogeneous process so that the classic theory is revised.展开更多
2020年3月18日中午至夜间,山西、河北、北京、天津和山东等地先后出现阵风10级及以上强风天气。利用风廓线雷达、国家级地面气象观测站和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)第五代大气...2020年3月18日中午至夜间,山西、河北、北京、天津和山东等地先后出现阵风10级及以上强风天气。利用风廓线雷达、国家级地面气象观测站和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)第五代大气再分析数据(ECMWF Reanalysis v5,ERA5)等资料,对强风过程的天气学成因进行了分析。结果表明:强风发生在低空暖脊异常发展的热力环境条件下,冷锋自黄土高原下到华北平原,中层锋消,垂直方向上发生“断裂”,低层冷锋先行侵入热低压,在锋生过程中发生。强风具有显著的非地转瞬变特征,低层强冷平流是强变压梯度产生的主要因素,变压风叠加在快速移动的冷锋系统中诱发大风,变压风是重要组成部分;低空动量下传效应引起低层风速波动,但不足以直接诱发强风。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 92158204, 41506001 and 42076019)a Project supported by the Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (Grant No. 311021005)。
文摘The variations of the frontogenetic trend of a cold filament induced by the cross-filament wind and wave fields are studied by a non-hydrostatic large eddy simulation. Five cases with different strengths of wind and wave fields are studied.The results show that the intense wind and wave fields further break the symmetries of submesoscale flow fields and suppress the levels of filament frontogenesis. The changes of secondary circulation directions—that is, the conversion between the convergence and divergence of the surface cross-filament currents with the downwelling and upwelling jets in the filament center—are associated with the inertial oscillation. The filament frontogenesis and frontolysis caused by the changes of secondary circulation directions may periodically sharpen and smooth the gradient of submesoscale flow fields.The lifecycle of the cold filament may include multiple stages of filament frontogenesis and frontolysis.
基金supported by the National 973 Fundamental Research Program of the Ministry of Science and Technology of China (Grant No.2013CB430105)the Special Scientific Research Fund of the Meteorological Public Welfare of the Ministry of Sciences and Technology (Grant No.GYHY201406003)+1 种基金the National Natural Sciences Foundation of China (Grant Nos.41375054, 41375052 and 40805001)the Opening Foundation of the State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences (Grant Nos.2012LASW-B02 and 2013LASW-A06)
文摘With the definition of generalized potential temperature, a new generalized frontogenesis function, which is expressed as the Lagrangian change rate of the magnitude of the horizontal generalized potential temperature gradient, is derived. Such a frontogenesis function is more appropriate for a real moist atmosphere because it can reflect frontogenesis processes, in which the atmosphere in a frontal zone is typically characterized by neither completely dry nor uniform saturation. Furthermore, by derivation, the expression of generalized frontogenesis function includes both temperature and humidity gradients, which is different from and superior to the traditional frontogenesis function in moist processes, which also uses equivalent potential temperature. Diagnostic studies of real cases are performed and show that the generalized frontogenesis function in non- uniformly saturated moist atmosphere indeed provides a useful tool for frontogenesis, compared to using the traditional frontogenesis function. The new frontogenesis function can be used in situations involving either a strong temperature or moisture gradient and is closely correlated with precipitation.
基金supported by the National 973 Fundamental Research Program of the Ministry of Science and Technology of China (Grant No. 2013CB430105)the Key Research Program of the Chinese Academy of Sciences (Grant No. KZZD-EW-05-01)+2 种基金the Special Scientific Research Fund of the Meteorological Public Welfare of the Ministry of Sciences and Technology, China (Grant No. GYHY201406003)the National Natural Science Foundation of China (Grant Nos. 41375054, 41375052 and 40805001)the Opening Foundation of the State Key Laboratory of Severe Weather, Chinese Academy of Meteorological Sciences (Grant Nos. 2012LASW-B02 and 2013LASW-A06)
文摘A new frontogenesis function is developed and analyzed on the basis of a local change rate of the absolute horizontal gradient of the resultant deformation. Different from the traditional frontogenesis function, the newly defined deformation frontogenesis is derived from the viewpoint of dynamics rather than thermodynamics. Thus, it is more intuitive for the study of frontogenesis because the compaction of isolines of both temperature and moisture can be directly induced by the change of a flow field. This new frontogenesis function is particularly useful for studying the mei-yu front in China because mei-yu rainbands typically consist of a much stronger moisture gradient than temperature gradient, and involve large deformation flow. An analysis of real mei-yu frontal rainfall events indicates that the deformation frontogenesis function works remarkably well, producing a clearer mei-yu front than the traditional frontogenesis function based on a measure of the potential temperature gradient. More importantly, the deformation frontogenesis shows close correlation with the subsequent(6 h later) precipitation pattern and covers the rainband well, bearing significance for the prognosis or even prediction of future precipitation.
基金the National Natural Science Foundation of China under grants:!49675259 and 49735180, the State Key Basic Program' CHERES.
文摘If the initial fields are not in geostrophic balance, the adjustment and evolution will occur in the stratified fluid. and the frontogenesis will occur under suitable conditions. The evolution is studied here with a nonhydrostatic fully compressible meso-scale model (Advanced Regional Prediction System, ARPS). Four cases are designed and compared: (i) control experiment: (ii) with different initial temperature gradient; (iii) with vapor distribution; (iv) with orographic forcing. The results show that: (1) there is an inertial oscillation in the evolution of the imbalanced flow with the frequency of the local Coriolis f, and with its amplitude decreasing with time. The stationary balanced state can only be approached as it cannot be reached in the limit duration of time. The energy conversion ratio varies in the range of [0, 1; 3]; (2) the stronger initial temperature gradient can make the final energy conversion ratio higher. and vice versa; (3) suitable vapor distribution is favorable for the frontogenesis. It will bring forward the time of the frontogenesis, strengthen the intensity of the cold front, and influence the final energy conversion ratio; (4) the orographic forcing has an evidently strengthening effect on the frontogenesis. The strengthening effect on the frontogenesis and the influence on the final energy conversion ratio depend on the relative location of the mountain to the cold front.
文摘Observational study shows that, in some cases, the frontal structure displays the features of gravitative flows. It seems that the formation of discontinuity is an important problem in the study of the frontogenesis which is usually defined as an increasing of the scalar gradient. In this paper, the characteristic features of air flow with initial imbalance between the wind and the density fields are studied. Much attention is paid on the condition for the formation of discontinuity and its time scale. It is found that the initial distribution of density plays an important role in the formation of the discontinuity which happens in short time duration.
基金The project was supported by the Nutional Key Planning Development Project for Basic Research (G199903280l)the Key Innovition Project of the Chinese Academy of Sciences (KZCX2-208).
文摘The artificial compression method (ACM) that is generally used to capture the contact discontinuity in nonviscous flows is used here in the simulation of quasi-geostrophic ideal frontogenesis in two dimensions. A comparison is made among the result of the ACM, the simulation result of Cullen, and the exact solution of the semi-geostrophic equations. The simulated front in this paper is more prominent than Cullen′s and is much closer to the exact solution.
基金the National Natural Science Foundation of China (Grant Nos. 40205009, 40175005, 40075011) the Nanjing University Postdoctoral Foundation,the State Key Basic Program (CHERES).
文摘On the basis of the MM5 simulation data of the severe storm that occurred over the southeastern part of Hubei province on 21 July 1998, the interaction of mesoscale convection and frontogenesis is dealt with using the thermodynamical equation and frontogenetical function. The results show that the outbreak of the severe storm is closely related to the local frontogenesis. In fact, the interaction between the shearing instability of the low-level jet (LLJ) and the topographic forcing generates an gravity-inertia wave as well as local frontogenesis (the ?rst front), which consequently induce the onset of the severe storm. From then on, owing to the horizontal and vertical advection of the potential temperature, the new frontogenesis (the second front) is formed to the northeast side of the severe storm, which initiates the second rain belt. Meanwhile, a two-front structure emerges over the southeastern part of Hubei province. Accompanied with the further intensi?cation of the convection, the rain droplets evaporation cooling strengthens the ?rst front and weakens the second front, resulting in single front structure over the southeastern part of Hubei province in the period of the strong convection.
文摘Using the PSU/NCAR Mesoscale Model version four(MM4), the frontogenesis and geostrophic adjustment problem in atmosphere with imbalance initial ideal data and conditions are studied. Based on results of experiments, it is found that the objective analysis and initialization procedure of the Model are not sensitive to the initial conditions used in this study. The final state of atmosphere, through process of adjustment, depends on the temperature gradient intensity of initial imbalance conditions. The front can be formed with appropriate condition. The processes of the frontogenesis are studied. It is also found that the response of the model to the ideal initial data used in this investigation is sensitive to the selected lateral boundary condition. The time-dependent inflow/outflow lateral boundary condition is the best implemented option for this numerical study. Energetic study of the experiments shows that the front is formed after the initial transient stage when there is no exchange of energy between the kinetic and potential energy. The time needed for the formation of the front is longer than that predicted theoretically. The ratio of kinetic energy to the released potential energy is considered. This ratio varies with the temperature gradient intensity and the type of used wind for computing kinetic energy (geostrophic or geostrophic plus ageostrophic wind). The larger temperature gradient, the larger magnitude of this ratio. A maximum value of energy in either type of computed kinetic energies (geostrophic wind kinetic energy and actual wind kinetic energy) for cases that the fronts are observed whereby, and its magnitude and occurrence time depend on initial data distribution. The variation of the computed kinetic energies with time, after transition time, is reasonable and no significant conversion of the energy between kinetic and potential energy goes on, however, stability within variables is not achieved.
基金Key National Fundamental Research (2010CB951904)National Science Foundation of China(41075034+1 种基金10871099)Natural Science Foundation of Jiangsu (BK2010128)
文摘This paper diagnoses and analyses the developmental mechanism of a process of extratropical transition of a tropical cyclone which occurred over West Pacific Ocean based on a diagnosis method of potential vorticity inversion of frontogenesis.The study diagnoses quantitatively the role and effect of dynamic influence of westerly cold troughs,middle-latitude baroclinic frontal zones,cyclone cycles and unbalanced wind fields during the different stages of the extratropical transition of a tropical cyclone,and also discusses the interaction between them and the developmental mechanism.The results show that there are different developmental mechanisms during each stage of the extratropical transition and the processes are also unbalanced.
文摘A two-dimensional mesoscale model is used to investigate the effect of background wind field andcharacter of the underlying surface on the coastal frontogenesis along the east continental coast when cold air outbreak. The results of numerical experiments indicate that the coastal frontogenesis mainly appears near ground atnight. When the background wind is easterly, it is favorable to coastal frontogenesis in the lower layer of the atmosphere. When the background wind is westerly, it is unfavorable to coastal frontogenesis in the lower layer of theatmosphere. The vertical shear of the background wind has important influence on the coastal frontogenesis. Thecoastal frontogenesis at lower layer at night is strengthened with increasing temperature difference between sea andair. The effect of coastal sloping terrain on the coastal frontogenesis is little when the topography sloping angle islesser.The analysis of the physical mechanism of frontogenesis shows that the main factor influencing the coastalfrontogenesis is the deformation field of horizontal wind speed.
基金This work was supported by the National Natural Science Foundation of China
文摘This paper improves Bannon's work on the quasi-geostrophic frontogenesis in a horizontal deformation field. By setting the lower boundary condition for the equation of potential temperature on the realistic topography instead of on z = 0, a general solution for the temperature field is derived after applying conformal mapping to the equation for the potential temperature, the vertical velocity and divergence field are also calculated. The general characteristics for the frontogenetic process still are frontolytic for warm front and frontogenetic for cold front in downstream of a mountain and the reverse is true upstream of a mountain, but more fine spatial structure of the temperature field and frontogenetic characteristics than Bannon's are obtained near surface because of the treatment of lower boundary condition. It is concluded that the frontogenetic characteristics are related to the translating speed of the deformation field with respect to the topography.
文摘A method of linear momentum approximation is proposed that deals with weak nonlinear problems in an approximate manner. A motion of nonlinear nature is obtained in the system by assuming the motion to be in the form of linear momentum flow in the corresponding space introduced, followed by the transformation from the specified into a physical space. Significant results have been thereby derived in examining the effects of baroclinic Ekman momentum flow upon Eady-type baroclinic waves and frontogenesis. Also, this technique can be applied to investigate the dynamic characteristics of the weak nonlinear boundary layer including topography, stratification and non-Ekmantype friction for gaining further insight into the influence on the boundary layer inner parameters of terrain, baroclinicity and inhomogeneous process so that the classic theory is revised.
文摘2020年3月18日中午至夜间,山西、河北、北京、天津和山东等地先后出现阵风10级及以上强风天气。利用风廓线雷达、国家级地面气象观测站和欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts, ECMWF)第五代大气再分析数据(ECMWF Reanalysis v5,ERA5)等资料,对强风过程的天气学成因进行了分析。结果表明:强风发生在低空暖脊异常发展的热力环境条件下,冷锋自黄土高原下到华北平原,中层锋消,垂直方向上发生“断裂”,低层冷锋先行侵入热低压,在锋生过程中发生。强风具有显著的非地转瞬变特征,低层强冷平流是强变压梯度产生的主要因素,变压风叠加在快速移动的冷锋系统中诱发大风,变压风是重要组成部分;低空动量下传效应引起低层风速波动,但不足以直接诱发强风。