环境流场垂直切变对热带气旋强度变化的影响研究

The change in tropical cyclone (TC) intensity is the challenge in the area of TC research. The effect of vertical shear of environment flow on the change in TC intensity is most important issue. The TC intensity variation in Northwest Pacific is analysised and some typical cases of TC intensity change are diagnosed using the NCEP re-analysis data. Also the slantwise vorticity development theory is used in the abrupt change in TC intensity. Finally the mechanism is investigated by means of numerical model of TC. . The diagnostic result show that the development of a tropical cyclone in the environmental flow is arrested. A TC could develop further in the environmental of small vertical shear.. A limited-area primitive equation model is used to study the effect of planetary vorticity gradient and uniform current on tropical cyclone (TC) intensity. It is found that TC intensity is reduced in a non-quiescent environment compared with the case of no mean flow. A TC on a beta plane not only intensifies slower than one on an f plane, its rate of intensification also varies with the direction of the mean flow.. The main physical characteristic that distinguishes the experiments is the asymmetric thermodynamic (including convective) and dynamic structures present when either a mean flow or a planetary vorticity gradient is introduced. On the other hand, a fairly symmetric TC structure is simulated on an f-plane...The magnitude of the warm core and the associated subsidence are found to be responsible for such simulated intensity changes. On an f plane, the convection tends to be symmetric, which results in strong upper-level convergence near the center and hence strong forced subsidence and a very warm core. On the other hand, horizontal advection of temperature cancels part of the adiabatic heating and results in less warming of the core, and hence the TC is not as intense. This advective process is due to the tilt of vortex as a result of the beta-effect. A similar situation occurs in the presence of a uniform flow. Thus, the asymmetric horizontal advection of temperature plays an important role in the temperature distribution.. Also based on moist potential vorticity equation and the theory of slantwise vorticity development(SVD), the possible relationaship between the abrupt intensity change of TC and evolution of its equivalent potential temperature structure is studed. The result indicates that because the moist isentropic surface are extremely steep in the eyewall region, the change of moist baroclinity is a main cause for abrupt change of vertical svelocity there. The result also indicates that SVD could be used in the research of change in TC intensity. It means SDV is a new means for TC intensity change study..

. 根据再分析资料和西北太平洋热带气旋（TC）资料，分析环境流场垂直切变对TC强度变化的影响。建立TC强度数值模式，进行环境流场垂直切变对TC强度变化的数值模拟和数值试验，据此分析在垂直切变环境流场中TC的动力和热力结构的变化特征。用倾斜位涡发展理论诊断分析环境流场垂直切变对TC强度变化影响的物理机制，从而认识TC强度变化的某些机理，并为TC强度预报提供理论依据。