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Vertical Velocity Structures in an Axisymmetric, Nonhydrostatic Tropical Cyclone Model

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  • 1 Hurricane Research Division/AOML/NOAA, Miami, Florida
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Abstract

A statistical analysis of several experiments with different microphysical parameterizations in an axisymmetric, nonhydrostatic tropical cyclone model illustrates the impact of icc-phase microphysics on model vertical velocity structure. The parameterizations are designed to illustrate the effects of 1) thermodynamic input through latent heating, 2) vertical sorting of microphysical species by fallspeed, and 3) different rates of the parameterized microphysical conversion processes. The results confirm previous studies on the thermodynamic effect of melting, but they also show that the other factors, namely, fallspeed and microphysical conversion rates, are important in determining model vertical velocity structure and evolution. Statistical summaries of updrafts and downdrafts show distinct increases in the intensity and horizontal scale of downdrafts near the melting level when parameterized snow is included. Model storms without snow show a greater percentage of convective-scale updrafts and downdrafts; they intensify more slowly but ultimately become stronger than those that have larger scale vertical velocity structures.

Abstract

A statistical analysis of several experiments with different microphysical parameterizations in an axisymmetric, nonhydrostatic tropical cyclone model illustrates the impact of icc-phase microphysics on model vertical velocity structure. The parameterizations are designed to illustrate the effects of 1) thermodynamic input through latent heating, 2) vertical sorting of microphysical species by fallspeed, and 3) different rates of the parameterized microphysical conversion processes. The results confirm previous studies on the thermodynamic effect of melting, but they also show that the other factors, namely, fallspeed and microphysical conversion rates, are important in determining model vertical velocity structure and evolution. Statistical summaries of updrafts and downdrafts show distinct increases in the intensity and horizontal scale of downdrafts near the melting level when parameterized snow is included. Model storms without snow show a greater percentage of convective-scale updrafts and downdrafts; they intensify more slowly but ultimately become stronger than those that have larger scale vertical velocity structures.

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