An Eigenfrequency Analysis of Mixed Rossby-Gravity Waves on Barotropic Vortices
- 作者：WEI ZHONGDA-LIN ZHANG
- 会议时间：2014-09-10
- 作者单位：WEI ZHONG(Key Laboratory of Mesoscale Severe Weather, Nanjing University, and Nanjing Institute of Mesoscale Meteorology, Nanjing, China)DA-LIN ZHANG(Department of Atmospheric and Oceanic Science, University of Maryland, College Park, College Park, Maryland)
- 母体文献：第八届全国优秀青年气象科技工作者学术研讨会论文集
- 会议名称：第八届全国优秀青年气象科技工作者学术研讨会
- 会议地点：江苏宜兴
- 主办单位：中国气象学会
- 语种：chi
摘要
In this study, the linearized, f-plane, shallow-water equations are discretized into a matrix eigenvalue problem to examine the full spectrum of free waves on barotropic (monopolar and hollow) vortices.A typical wave spectrum for weak vortices shows a continuous range between zero and an advective frequency asso ciated with vortex Rossby waves (VRWs) and two discrete ranges at both sides associated with inertio-gravity waves (IGWs).However, when the vortex intensity reaches a critical value, higher-frequency waves will be "red shifted" into the continuous spectrum, while low-frequency waves will be "violet shifted" into the discrete spectrum, leading to the emergence of mixed vortex Rossby-inertio-gravity waves (VRIGWs).Results show significant (little) radial wavelike structures of perturbation variables for IGWs (VRWs) with greater (much smaller) divergence than vorticity and the hybrid IGW-VRW radial structures with equal amnlitudes of vorticitv and divergence for mixed VRIGWs.In addition.VRWs only occur within a critical radius at which the perturbation azimuthal velocity is discontinuous.As the azimuthal wavenum her increases.lower-frequency waves tend to exhibit more mixed-wave characteristics, whereas higher-frequency waves will be more of the IGW type.Two-dimensional wave solutions show rapid outward energy dispersion of IGWs and slower dispersion of VRWs and mixed VRIGWs in the core region.These solutions are shown to re semble the previous analytical solutions, except for certain structural differences caused by the critical radius.It is concluded that mixed VRIGWs should be common in the eyewall and spiral rainbands of intense tropical cyclones.Some different wave behaviors associated with the monopolar and hollow vortices are also discussed.