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Tropical cyclone size: in observations, at equilibrium, and in risk assessment

Speaker: Dan Chavas, MIT
Series: CEE Departmental Seminars
Location: Friend Center 004
Date/Time: Friday, March 1, 2013, 1:30 p.m. - 3:00 p.m.

Abstract:

Dan Chavas
Tropical cyclone size remains an unsolved problem in tropical meteorology, yet size strongly modulates damage risk due to wind, storm surge, and inland freshwater flooding. This work explores the physical determinants of tropical cyclone size and structure at equilibrium in an idealized state of radiative-convective equilibrium (RCE), the simplest representation of an Earth-like tropical climate. We find that the equilibrium radial wind profile is primarily a function of a single non-dimensional parameter given by the ratio of the storm radial length scale to the parameterized eddy radial length scale, with a secondary non-dimensional parameter modulating only the far outer circulation. The storm radial length scale is found to be the ratio of the potential intensity, which is the theoretical upper bound on storm wind speed, to the Coriolis parameter, matching the prediction for the "natural" storm length scale embedded within prevailing axisymmetric tropical cyclone theory. More broadly, this talk will place our understanding of storm size within the context of hurricane risk assessment.