A parameterization of the boundary layer of a tropical cyclone |
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| Authors: | L Bode R K Smith |
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| Institution: | (1) Dept. of Applied Mathematics, University of Edinburgh, Edinburgh, Scotland, U.K.;(2) Present address: Department of Mathematics, University of Papua New Guinea, Port Moresby, Papua New Guinea;(3) Present address: Department of Mathematics, Monash University, Melbourne, Australia |
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| Abstract: | In an earlier paper by one of the authors (Smith, 1968), a momentum integral method was developed to parameterize the gross
constraint imposed by the surface boundary layer of a steady, axisymmetric, tropical cyclone on the meridional circulation
within the vortex itself. Specifically, the method provides an effective means of estimating the radial variation of mean
upflow/downflow induced by the boundary layer, compatible with a prescribed radial variation of azimuthal velocity just above
the boundary layer,V
gr. However, it relies on a judicious choice of vertical profiles of radial and azimuthal velocity components within the boundary
layer. An especially suitable set of profiles is discussed herein; these are Ekman-like profiles in which turbulent mixing
is characterized by a vertically constant eddy diffusivityK
M
, matched to a constant stress sublayer just above the sea surface. An attractive feature of the formulation is that a suitable
value forK
M
as a function of radius, which is extremely difficult to extract from observational data, can be calculated when the state
of the sea surface, described by a roughness lengthZ
0, is prescribed. Although observations ofZ
0 at high wind speeds are not yet available, the effect of radial variations in sea surface roughness can be assessed and it
is shown that these affect the upflow to a significant degree. |
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| Keywords: | |
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