摘要
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.
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.
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
