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A time‐dependent Lagrangian eyewall
Author(s) -
Rutherford Blake,
Dangelmayr Gerhard,
Kirby Michael
Publication year - 2012
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.1920
Subject(s) - eye , ridge , lagrangian , geology , tropical cyclone , meteorology , mechanics , mathematics , geometry , physics , climatology , mathematical analysis , paleontology
The structure of a tropical cyclone eye and eyewall plays an important role in intensification. While the eyewall is usually defined in terms of instantaneous velocity and derived quantities such as vorticity, or thermodynamic variables such as equivalent potential temperature, or pressure, a Lagrangian eyewall definition is based on the transport of particles. In this paper, we analyse a Lagrangian eye–eyewall interface (LEEI), which is defined as a surface that acts as barrier to particle motion. The surface is identified with a maximal ridge of a hyperbolic Lagrangian field, and varies with the initial time at which particles are seeded. Our study extends a previous LEEI construction (Rutherford B, Dangelmayr G. 2010. Q. J. R. Meteorol. Soc. 136: 1931–1944) as follows. First, the ridge extraction algorithm used in our previous work is fully automated over time and z ‐levels, and smoothed by representing the ridge curves on z ‐slices in terms of Fourier descriptors. Secondly, the ridge curves for varying z ‐levels are matched to vertical basis functions leading to a 3D spatially continuous and low‐dimensional representation of the LEEI, by truncating the combined azimuthal and vertical expansion. The surface is then analysed over varying initial time, and structural differences in time and height show that differences in Lagrangian structure and the degree of axisymmetry correspond to changes in intensity. Copyright © 2012 Royal Meteorological Society