P2D.7 Sensitivity of Tropical Cyclone Intensity to the Representation of Ice Microphysics

Thursday, 1 May 2008
Palms ABCD (Wyndham Orlando Resort)
Yi Jin, NRL, Monterey, CA; and J. D. Doyle, J. Schmidt, and S. Wang

Microphysical processes play an important role in intensity and structural changes of tropical cyclones (TC). In order to make skillful forecasts of TC development, it is necessary to accurately describe complex processes involving ice microphysics, such as conversions between ice and other species, latent heating release associated with ice processes, and radiative cooling and heating near ice cloud layers. In this study, high resolution COAMPS simulations are performed to evaluate the impact of different formulations of ice nuclei concentration on TC intensity. It is discovered from our sensitivity experiments that an order of magnitude of difference in ice concentration at upper levels in the hurricane eyewall and anvil clouds results from established parameterizations of ice nuclei concentration. The storm intensity, thermodynamic structure, and turbulence distributions are substantially altered by varying the ice nuclei concentration. The difference between simulations could reach 32 hPa in mean sea level pressure and 40 m s-1 in surface maximum winds. A discussion of model results will include a comparison of simulated ice fields with ice observations obtained in hurricanes. Given the extreme sensitivity of tropical cyclone intensity to ice processes, this study motivates the need for more research in both modeling of ice microphysical processes and observational measurements of ice nuclei concentration in hurricanes.
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