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- Author or Editor: Jacqueline M. Lord x
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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.
Abstract
Results of an axisymmetric, nonhydrostatic hurricane model are analyzed with emphasis on the role of a parameterized ice-phase microphysics Inclusion of ice processes produces dramatic differences in the structure and evolution of the simulated hurricane vortex. Mesoscale convective features are wore plentiful with ice, and the simulated vortex grows more slowly.
Time and space-averaged budgets of key model varibles show that cooling due to melting ice particles can initiate and maintain model downdrafts on a horizontal scale of tens of kilometers. This scale depends critically on both the horizontal advection of the parameterized snow particles detrained from the tops of convective updrafts and the mean fall speed of the particles toward the melting level. In situ0 production of snow particles results from a wide variety of parameterized microphysical processes and is significant factor in maintaining upper-level snow concentration These processes are strongly height-dependent.
Abstract
Results of an axisymmetric, nonhydrostatic hurricane model are analyzed with emphasis on the role of a parameterized ice-phase microphysics Inclusion of ice processes produces dramatic differences in the structure and evolution of the simulated hurricane vortex. Mesoscale convective features are wore plentiful with ice, and the simulated vortex grows more slowly.
Time and space-averaged budgets of key model varibles show that cooling due to melting ice particles can initiate and maintain model downdrafts on a horizontal scale of tens of kilometers. This scale depends critically on both the horizontal advection of the parameterized snow particles detrained from the tops of convective updrafts and the mean fall speed of the particles toward the melting level. In situ0 production of snow particles results from a wide variety of parameterized microphysical processes and is significant factor in maintaining upper-level snow concentration These processes are strongly height-dependent.
Abstract
This paper reports numerical simulations of the hurricane vortex by an axisymmetric, nonhydrostatic numerical model with 2 km maximum horizontal resolution. Moist convection is modeled explicitly using two different microphysical parameterizations. The first simulates liquid water processes only, whereas the second includes ice processes as well.
Although concentric rings of convection associated with local maxima of the tangential wind form in both versions of the model, they are much more common when ice processes are included. As they contract about the vortex center, the outer ones supplant the inner. Their contraction follows the mechanism suggested by balanced-vortex models. Some of the rings appear to form through symmetric instability of the vortex, and others—particularly when ice processes are included—through interactions between precipitation-induced downdrafts and the boundary layer. Both the rings’ evolution and the detailed structure of the vortex core are similar to recent aircraft and radar observations. Among the realistic features are: outward slope of the eyewall updraft and tangential wind maximum; relative location of the updraft, wind maximum, and precipitation maximum; stratiform precipitation and mesoscale downdrafts outside the eye; and midlevel radial inflow.
Abstract
This paper reports numerical simulations of the hurricane vortex by an axisymmetric, nonhydrostatic numerical model with 2 km maximum horizontal resolution. Moist convection is modeled explicitly using two different microphysical parameterizations. The first simulates liquid water processes only, whereas the second includes ice processes as well.
Although concentric rings of convection associated with local maxima of the tangential wind form in both versions of the model, they are much more common when ice processes are included. As they contract about the vortex center, the outer ones supplant the inner. Their contraction follows the mechanism suggested by balanced-vortex models. Some of the rings appear to form through symmetric instability of the vortex, and others—particularly when ice processes are included—through interactions between precipitation-induced downdrafts and the boundary layer. Both the rings’ evolution and the detailed structure of the vortex core are similar to recent aircraft and radar observations. Among the realistic features are: outward slope of the eyewall updraft and tangential wind maximum; relative location of the updraft, wind maximum, and precipitation maximum; stratiform precipitation and mesoscale downdrafts outside the eye; and midlevel radial inflow.
