Abstract
Under the adiabatic, axisymmetric and steady assumption, a relationship between the saturated moist entropy structure and the secondary circulation in a tropical cyclone (TC) is derived from the continuity equation. It is found that the isentropic surfaces coincide with the streamlines, and the streamfunction can be expressed with saturated moist entropy. The secondary circulation and the saturated moist entropy structure depend on each other. Thus, a method for diagnosing the secondary circulation with the structure of saturated moist entropy is proposed. The method is verified with a simulated intense ideal-ized TC with a highly axisymmetric structure. The diagnosed secondary circulation reproduces well the moist inflow in the boundary layer and the moist updraft in the eyewall. This method facilitates secondary circulation diagnosis in theoretical or mature TCs that satisfy the adiabatic, axisymmetric and steady approximations.
摘 要
基于绝热, 轴对称和定常假设, 从连续方程导出热带气旋的饱和湿熵结构与次级环流的关系. 推导结果证明, 在假设条件满足的情况下, 流线与等熵面重合, 流函数可以用饱和湿熵的函数表示, 饱和湿熵结构与次级环流互相关联. 由此提出从饱和湿熵结构诊断次级环流的方法. 利用模拟的具有高度轴对称结构的理想强热带气旋对诊断方法进行验证, 结果表明, 诊断得到的次级环流较好地重现了边界层入流和眼墙上升气流结构. 对于理论的热带气旋或满足绝热, 轴对称和定常近似的成熟热带气旋, 该诊断方法简化了其次级环流的诊断.
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Article Highlights
• With the steady, adiabatic and axisymmetric assumptions, a method for diagnosing the secondary circulation from entropy is proposed.
• The diagnosis method is simpler than the Sawyer-Eliassen equation.
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Huang, Y., Duan, Y., Chan, J.C.L. et al. A Method for Diagnosing the Secondary Circulation with Saturated Moist Entropy Structure in a Mature Tropical Cyclone. Adv. Atmos. Sci. 36, 804–810 (2019). https://doi.org/10.1007/s00376-019-9054-5
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DOI: https://doi.org/10.1007/s00376-019-9054-5