By employing the energy-Casimir method, a three-dimensional virtual pseudoenergy wave-activity relation for a moist atmosphere is derived from a complete system of nonhydrostatic equations in Cartesian coordinates. Si...By employing the energy-Casimir method, a three-dimensional virtual pseudoenergy wave-activity relation for a moist atmosphere is derived from a complete system of nonhydrostatic equations in Cartesian coordinates. Since this system of equations includes the effects of water substance, mass forcing, diabatic heating, and dissipations, the derived wave-activity relation generalizes the previous result for a dry atmosphere. The Casimir function used in the derivation is a monotonous function of virtual potential vorticity and virtual potential temperature. A virtual energy equation is employed （in place of the previous zonal momentum equation） in the derivation, and the basic state is stationary but can be three-dimensional or, at least, not necessarily zonally symmetric. The derived wave-activity relation is further used for the diagnosis of the evolution and propagation of meso-scale weather systems leading to heavy rainfall. Our diagnosis of two real eases of heavy precipitation shows that positive anomalies of the virtual pseudoenergy wave-activity density correspond well with the strong precipitation and are capable of indicating the movement of the precipitation region. This is largely due to the cyclonic vorticity perturbation and the vertically increasing virtual potential temperature over the precipitation region.展开更多
Taking into account moisture in virtue of general potential temperature,the author derive a three-dimensional(3D) pseudomomentum wave-activity relation for the moist atmosphere from the primitive equations in Cartesia...Taking into account moisture in virtue of general potential temperature,the author derive a three-dimensional(3D) pseudomomentum wave-activity relation for the moist atmosphere from the primitive equations in Cartesian coordinates using the Momentum-Casimir method.Since the wave-activity relation is constructed in an ageostrophic and non-hydrostatic dynamical framework,it may be applicable to diagnosing the evolution and propagation of mesoscale systems leading to heavy rainfall.The theoretical analysis shows that,besides the local change of wave-activity flux divergence and source or sink,the wave-activity relation includes two additional forcing terms.The first is the zonal gradient of difference between general potential temperature and potential temperature perturbations,and the second is the covariance of the solenoid and gradient of water vapor,denoting the direct influence of moisture on wave-activity density.The wave-activity density was applied to a heavy precipitation event occurring in the Jianghuai region of China.The calculation showed that the wave-activity density was consistent with 6-h accumulated precipitation observations,in terms of both spatial distribution and temporal tendency.This suggested that the disturbance represented by wave-activity density was closely related to the heavy precipitation.Although the wave-activity flux divergence and the covariance of the solenoid and gradient of water vapor made the primary contribution to the local change of wave-activity density,the covariance was more remarkable.The zonal gradient of difference between general potential temperature and potential temperature perturbations made a weaker contribution to the waveactivity density.展开更多
On the basis of the general potential vorticity theorem(GPV),a new wave-activity relation is derived in an ageostrophic and nonhydrostatic dynamic framework.When the Reynolds average is taken,the wave-activity relatio...On the basis of the general potential vorticity theorem(GPV),a new wave-activity relation is derived in an ageostrophic and nonhydrostatic dynamic framework.When the Reynolds average is taken,the wave-activity relation shares an exchange term with the equation of the basic-state GPV.Thus,the two equations are capable of presenting the dynamic process of the wave-basic flow interaction.Unlike the E-P flux theory which can only be used in large-scale atmosphere,the corresponding derivation provides a useful tool to analyze the feedback of waves to basic states and the forcing of basic states to waves simultaneously,and it can be used in mesoscale systems,such as heavy rainfall processes.The theory was initially applied to the landfalling Typhoon Mujigae(2015) by assigning the scalar φ to the generalized potential temperature(GPT).The results showed that the newly-derived wave-activity density is able to describe the wave activities associated with strong precipitation in Typhoon Mujigae(2015),including the eyewall and spiral rainbands.However,the interaction between the basic-state vortex and mesoscale waves denoted by the exchange term between basic-state GPV and wave-activity density mainly occurs in the eyewall in Typhoon Mujigae(2015).A comparison of the exchange term with other forcing terms in the newly-derived wave-activity relation indicates that the basic state-wave interaction plays a significant role in enhancing wave activities in the high-precipitation eyewall.By a magnitude analysis of the interaction term,it is found that the strong interaction between basic-state vortex and mesoscale waves is mainly attributed to two factors:the vertical vorticity intensity of the basic-state vortex and the averaged perturbation advection of perturbation GPT which is an exchange between the basic-state GPT and perturbation GPT.展开更多
Motivated by ageostrophic interactions of wave and basic flow,the generalized relationships between 3-dimensional Eliassen-Palm flux and basic flows,which are suitable for small-amplitude and finite-amplitude disturba...Motivated by ageostrophic interactions of wave and basic flow,the generalized relationships between 3-dimensional Eliassen-Palm flux and basic flows,which are suitable for small-amplitude and finite-amplitude disturbances,are derived.The local area-averaged and density-weighted mean flows are chosen as the basic flows.Under the assumption that the steady basic flows vary slowly in time and space,a quasi-conservative law of small amplitude wave activity is derived from Ertel's potential vorticity equation in isentropic coordinates. The expressions of the new 3-D Eliassen-Palm flux and wave activity are presented in terms of Eulerian quantities so that they can be readily calculated by using observation data or model output data.展开更多
A generalized wave-activity density, which is defined as an absolute value of production of three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation, is introduced and...A generalized wave-activity density, which is defined as an absolute value of production of three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation, is introduced and its wave-activity law is derived in Cartesian coordinates. Constructed in an agoestrophic and nonhydrostatie dynamical framework, the generalized wave-activity law may be applicable to diagnose mesoscale weather systems leading to heavy rainfall. The generalized wave-activity density and wave-activity flux divergence were calculated with the objective analysis data to investigate the character of wave activity over heavy-rainfall regions. The primary dynamical processes responsible for disturbance associated with heavy rainfall were also analyzed. It was shown that the generalized wave-activity density was closely correlated to the observed 6-h accumulative rainfall. This indicated that the wave activity or disturbance was evident over the frontal and landfall-typhoon heavy-rainfall regions in middle and lower troposphere. For the landfall-typhoon rainband, the portion of generalized wave-activity flux divergence, denoting the interaction between the basic-state cyclonic circulation of landfall typhoon and mesoscale waves, was the primary dynamic process responsible for the evolution of generalized wave-activity density.展开更多
Taking into account the effect of moisture,we derive a three-dimensional pseudoenergy wave-activity relation for moist atmosphere from the primitive zonal momentum and total energy equations in Cartesian coordinates b...Taking into account the effect of moisture,we derive a three-dimensional pseudoenergy wave-activity relation for moist atmosphere from the primitive zonal momentum and total energy equations in Cartesian coordinates by using the energy-Casimir method.In the derivation,a Casimir function is introduced,which is a single-value function of virtual potential temperature.Since the pseudoenergy wave-activity relation is constructed in the ageostrophic and nonhydrostatic dynamical framework,it may be applicable to diagnosing the stability of mesoscale disturbance systems in a steady-stratified atmosphere.The theoretical analysis shows that the wave-activity relation takes a nonconservative form in which the pseudoenergy wave-activity density is composed of perturbation kinetic energy,available potential energy,and buoyant energy.The local change of pseudoenergy wave-activity density depends on the combined effects of zonal basic flow shear,Coriolis force work and wave-activity source or sink as well as wave-activity flux divergence.The diagnosis shows that horizontal distribution and temporal trend of pseudoenergy wave-activity density are similar to those of the observed 6-h accumulated surface rainfall.This suggests that the pseudoenergy wave-activity density is capable of representing the dynamical and thermodynamic features of mesoscale precipitable systems in the mid-lower troposphere,so it is closely related to the observed surface rainfall. The calculation of the terms in the wave-activity relation reveals that the wave-activity flux divergence shares a similar temporal trend with the local change of pseudoenergy wave-activity density and the observed surface rainfall.Although the terms of zonal basic flow shear and Coriolis force contribute to the local change of pseudoenergy wave-activity density,the contribution from the wave-activity flux divergence is much more significant.展开更多
基金supported by the National Basic Research Program of China(Grant No.2013CB430105)the Key Program of the Chinese Academy of Sciences(Grant No.KZZD-EW-05)+1 种基金the National Natural Science Foundation of China(Grant No.41175060)the Project of CAMS,China(Grant No.2011LASW-B15)
文摘By employing the energy-Casimir method, a three-dimensional virtual pseudoenergy wave-activity relation for a moist atmosphere is derived from a complete system of nonhydrostatic equations in Cartesian coordinates. Since this system of equations includes the effects of water substance, mass forcing, diabatic heating, and dissipations, the derived wave-activity relation generalizes the previous result for a dry atmosphere. The Casimir function used in the derivation is a monotonous function of virtual potential vorticity and virtual potential temperature. A virtual energy equation is employed （in place of the previous zonal momentum equation） in the derivation, and the basic state is stationary but can be three-dimensional or, at least, not necessarily zonally symmetric. The derived wave-activity relation is further used for the diagnosis of the evolution and propagation of meso-scale weather systems leading to heavy rainfall. Our diagnosis of two real eases of heavy precipitation shows that positive anomalies of the virtual pseudoenergy wave-activity density correspond well with the strong precipitation and are capable of indicating the movement of the precipitation region. This is largely due to the cyclonic vorticity perturbation and the vertically increasing virtual potential temperature over the precipitation region.
基金supported by the National Basic Research Program of China (Grant No.2009CB421505)the Key Program of the Chinese Academy of Sciences (Grant No.KZZD-EW-05)+2 种基金the project of Chinese Academy of Meteorological Sciences (Grant No.2011LASW-B15)the Spectial Scientific Research Fund of Meteorological Public Welfare of the Ministry of Sciences and Technology (Grant No.GYHY200906004)and the National Natural Science Foundation of China (Grant Nos.41175060,41075098,and 41005005)
文摘Taking into account moisture in virtue of general potential temperature,the author derive a three-dimensional(3D) pseudomomentum wave-activity relation for the moist atmosphere from the primitive equations in Cartesian coordinates using the Momentum-Casimir method.Since the wave-activity relation is constructed in an ageostrophic and non-hydrostatic dynamical framework,it may be applicable to diagnosing the evolution and propagation of mesoscale systems leading to heavy rainfall.The theoretical analysis shows that,besides the local change of wave-activity flux divergence and source or sink,the wave-activity relation includes two additional forcing terms.The first is the zonal gradient of difference between general potential temperature and potential temperature perturbations,and the second is the covariance of the solenoid and gradient of water vapor,denoting the direct influence of moisture on wave-activity density.The wave-activity density was applied to a heavy precipitation event occurring in the Jianghuai region of China.The calculation showed that the wave-activity density was consistent with 6-h accumulated precipitation observations,in terms of both spatial distribution and temporal tendency.This suggested that the disturbance represented by wave-activity density was closely related to the heavy precipitation.Although the wave-activity flux divergence and the covariance of the solenoid and gradient of water vapor made the primary contribution to the local change of wave-activity density,the covariance was more remarkable.The zonal gradient of difference between general potential temperature and potential temperature perturbations made a weaker contribution to the waveactivity density.
基金Project supported by the Strategic Pilot Science and Technology Special Program of the Chinese Academy of Sciences(Grant No.XDA17010105)the National Key Research and Development Project,China(Grant No.2018YFC1507104)+1 种基金the Key Scientific and Technology Research and Development Program of Jilin Province,China(Grant No.20180201035SF)the National Natural Science Foundation of China(Grant Nos.41875056,41775140,and 41575065)。
文摘On the basis of the general potential vorticity theorem(GPV),a new wave-activity relation is derived in an ageostrophic and nonhydrostatic dynamic framework.When the Reynolds average is taken,the wave-activity relation shares an exchange term with the equation of the basic-state GPV.Thus,the two equations are capable of presenting the dynamic process of the wave-basic flow interaction.Unlike the E-P flux theory which can only be used in large-scale atmosphere,the corresponding derivation provides a useful tool to analyze the feedback of waves to basic states and the forcing of basic states to waves simultaneously,and it can be used in mesoscale systems,such as heavy rainfall processes.The theory was initially applied to the landfalling Typhoon Mujigae(2015) by assigning the scalar φ to the generalized potential temperature(GPT).The results showed that the newly-derived wave-activity density is able to describe the wave activities associated with strong precipitation in Typhoon Mujigae(2015),including the eyewall and spiral rainbands.However,the interaction between the basic-state vortex and mesoscale waves denoted by the exchange term between basic-state GPV and wave-activity density mainly occurs in the eyewall in Typhoon Mujigae(2015).A comparison of the exchange term with other forcing terms in the newly-derived wave-activity relation indicates that the basic state-wave interaction plays a significant role in enhancing wave activities in the high-precipitation eyewall.By a magnitude analysis of the interaction term,it is found that the strong interaction between basic-state vortex and mesoscale waves is mainly attributed to two factors:the vertical vorticity intensity of the basic-state vortex and the averaged perturbation advection of perturbation GPT which is an exchange between the basic-state GPT and perturbation GPT.
基金the National Natural Science Foundation of China under Grant No.40175017the Innovation Project of Chinese Academy of Sciences under Grant No.KZCX3-SW-217
文摘Motivated by ageostrophic interactions of wave and basic flow,the generalized relationships between 3-dimensional Eliassen-Palm flux and basic flows,which are suitable for small-amplitude and finite-amplitude disturbances,are derived.The local area-averaged and density-weighted mean flows are chosen as the basic flows.Under the assumption that the steady basic flows vary slowly in time and space,a quasi-conservative law of small amplitude wave activity is derived from Ertel's potential vorticity equation in isentropic coordinates. The expressions of the new 3-D Eliassen-Palm flux and wave activity are presented in terms of Eulerian quantities so that they can be readily calculated by using observation data or model output data.
基金National Basic Research Program of China (2009CB421505)National Natural Sciences Foundations of China (40875032)
文摘A generalized wave-activity density, which is defined as an absolute value of production of three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation, is introduced and its wave-activity law is derived in Cartesian coordinates. Constructed in an agoestrophic and nonhydrostatie dynamical framework, the generalized wave-activity law may be applicable to diagnose mesoscale weather systems leading to heavy rainfall. The generalized wave-activity density and wave-activity flux divergence were calculated with the objective analysis data to investigate the character of wave activity over heavy-rainfall regions. The primary dynamical processes responsible for disturbance associated with heavy rainfall were also analyzed. It was shown that the generalized wave-activity density was closely correlated to the observed 6-h accumulative rainfall. This indicated that the wave activity or disturbance was evident over the frontal and landfall-typhoon heavy-rainfall regions in middle and lower troposphere. For the landfall-typhoon rainband, the portion of generalized wave-activity flux divergence, denoting the interaction between the basic-state cyclonic circulation of landfall typhoon and mesoscale waves, was the primary dynamic process responsible for the evolution of generalized wave-activity density.
基金Supported by the National Basic Research Program of China under Grant No.2009CB421505 the National Natural Sciences Foundation of China under Grant Nos.40875032,40405011 and 40475006
文摘Taking into account the effect of moisture,we derive a three-dimensional pseudoenergy wave-activity relation for moist atmosphere from the primitive zonal momentum and total energy equations in Cartesian coordinates by using the energy-Casimir method.In the derivation,a Casimir function is introduced,which is a single-value function of virtual potential temperature.Since the pseudoenergy wave-activity relation is constructed in the ageostrophic and nonhydrostatic dynamical framework,it may be applicable to diagnosing the stability of mesoscale disturbance systems in a steady-stratified atmosphere.The theoretical analysis shows that the wave-activity relation takes a nonconservative form in which the pseudoenergy wave-activity density is composed of perturbation kinetic energy,available potential energy,and buoyant energy.The local change of pseudoenergy wave-activity density depends on the combined effects of zonal basic flow shear,Coriolis force work and wave-activity source or sink as well as wave-activity flux divergence.The diagnosis shows that horizontal distribution and temporal trend of pseudoenergy wave-activity density are similar to those of the observed 6-h accumulated surface rainfall.This suggests that the pseudoenergy wave-activity density is capable of representing the dynamical and thermodynamic features of mesoscale precipitable systems in the mid-lower troposphere,so it is closely related to the observed surface rainfall. The calculation of the terms in the wave-activity relation reveals that the wave-activity flux divergence shares a similar temporal trend with the local change of pseudoenergy wave-activity density and the observed surface rainfall.Although the terms of zonal basic flow shear and Coriolis force contribute to the local change of pseudoenergy wave-activity density,the contribution from the wave-activity flux divergence is much more significant.
