Tropical cyclone flow asymmetries induced by a uniform flow revisited

Loading...
Thumbnail Image
Authors
Thomsen, Gerald L.
Smith, Roger K.
Montgomery, Michael T.
Subjects
Advisors
Date of Issue
2015-08-25
Date
Publisher
American Geophysical Union
Language
Abstract
We investigate the hypothesized effects of a uniform flow on the structural evolution of a tropical cyclone using a simple idealized, three-dimensional, convection-permitting, numerical model. The study addresses three outstanding basic questions concerning the effects of moist convection on the azimuthal flow asymmetries and provides a bridge between the problem of tropical cyclone intensification in a quiescent environment and that in the vertical shear over a deep tropospheric layer. At any instant of time, explicit deep convection in the model generates flow asymmetries that ten to mask the induced flow asymmetries predicted by the dry, slab boundary layer of Shapiro, whose results are frequently invoked as a benchmark for characterizing the boundary layer-induced vertical motion for a translating storm. In sets of ensemble experiment in which the initial low-level moisture field is randomly perturbed, time-averaged ensemble mean fields in the mature stage show a coherent asymmetry in the vertical motion rising into the eyewall and in the total (horizontal) wind speed just above the boundary layer. The maximum ascent occurs about 45 degrees to the left of the vortex motion vector, broadly in support of Shapiro's results, in which it occurs ahead of the storm, and consistent with one earlier more complex numerical calculation by Frank and Ritchie. The total wind asymmetry just above the boundary layer has a maximum in the forward right sector, which is in contrast to the structure effectively prescribed by Shapiro based on an inviscid dry symmetric vortex translating in a uniform flow where, in an Earth-relative frame, the maximum in on the right.
Type
Article
Description
The article of record as published may be found at: http://dx.doi.org10.1002/2015MS000477
Series/Report No
Department
Meteorology
Organization
Naval Postgraduate School (U.S.)
Identifiers
NPS Report Number
Sponsors
G.L.T. and R.K.S. were supported in part by grant SM 30/23-1 from the German Research Council (DFG). R.K.S. is supported also by the Office of Naval Research Global under grant N62909-15-1-N021. M.T.M. acknowledges the supports of NSF grants AGS-0733380 and NSF AGS-0851077 and NASA grants NNH09AK561 and NNG09HG031
Funder
Format
10 p.
Citation
Journal of Advances in Modeling Earth Systems, v.7, pp. 1265-1284
Distribution Statement
Approved for public release; distribution is unlimited.
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Collections