利用波作用理论对台风莫拉克登陆期间的降水进行诊断分析。结果表明:波作用密度异常能在一定程度上指示暴雨雨区发展移动,其异常值的空间分布能够反映雨区上空动力场和热力场的典型垂直结构特征。台风内中尺度波动与暴雨落区宏观上具有...利用波作用理论对台风莫拉克登陆期间的降水进行诊断分析。结果表明:波作用密度异常能在一定程度上指示暴雨雨区发展移动,其异常值的空间分布能够反映雨区上空动力场和热力场的典型垂直结构特征。台风内中尺度波动与暴雨落区宏观上具有一定联系。为了详细研究台风内部的波动特征,利用WRF(Weather Research and Forecasting model)模式模拟的高分辨率资料对台风登陆过程中波动特征进行分析,低波数波动的传播主导强对流的非对称分布,2波在登陆初期对对流分布起着关键作用,中尺度波动中同时存在涡旋罗斯贝波以及重力惯性波的特征,对登陆期间涡旋混合的现象有重要作用。展开更多
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 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
文摘利用波作用理论对台风莫拉克登陆期间的降水进行诊断分析。结果表明:波作用密度异常能在一定程度上指示暴雨雨区发展移动,其异常值的空间分布能够反映雨区上空动力场和热力场的典型垂直结构特征。台风内中尺度波动与暴雨落区宏观上具有一定联系。为了详细研究台风内部的波动特征,利用WRF(Weather Research and Forecasting model)模式模拟的高分辨率资料对台风登陆过程中波动特征进行分析,低波数波动的传播主导强对流的非对称分布,2波在登陆初期对对流分布起着关键作用,中尺度波动中同时存在涡旋罗斯贝波以及重力惯性波的特征,对登陆期间涡旋混合的现象有重要作用。
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 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.
