The Role of β-effect and a Uniform Current on Tropical Cyclone Intensity

• Published in: Advances in atmospheric sciences Vol. 21; no. 1; pp. 75 - 86
• Main Author: 端义宏 伍荣生 余晖 梁旭东 陈仲良
• Format: Journal Article
• Language: English
• Published: Shanghai Typhoon Institute,Shanghai 200030%Department of Atmosphere Science,Nanjing University,Nanjing 210008%Shanghai Typhoon Institute,Shanghai,200030%Dept.of Physics and Materials Science,City University of Hong Kong,Hong Kong 01-01-2004; Department of Atmosphere Science,Nanjing University,Nanjing 210008
• Subjects: 热力学试验; 热带气旋; 物理特征; asymmetric structure; uniform current; β-effect; tropical cyclone intensity change
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/BF02915681

A limited-area primitive equation model is used to study the role of the β-effect and a 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 uniform current. On an f-plane, the rate of intensification of a tropical cyclone is larger than that of the uniform flow. A TC on a β-plane intensifies slower than one on an f-plane. The main physical characteristic that distinguishes the experiments is the asymmetric thermodynamic (including convective) and dynamic structures present when either a uniform flow or β-effect is introduced. But 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 the vortex as a result of the β-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. Dynamically,the asymmetric angular momentum (AM) flux is very small on an f-plane throughout the troposphere. However, the total AM exports at the upper levels for a TC either on a β-plane or with a uniform flow environment are larger because of an increase of the asymmetric as well as symmetric AM export on the plane at radii >450 km, and hence there is a lesser intensification.