Three-dimensional numerical study of thunderstorm downdrafts and associated outflow boundaries /
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | Link to ProQuest copy Link to OAKTrust copy |
| Abstract: | Thunderstorm downdrafts and their associated outflow boundaries are numerically simulated using a high-resolution, time-dependent, three-dimensional model. The initial downdraft is initiated by specifying a distribution of precipitation at the top of the domain which initially has no vertical motion. Two initial thermodynamic profiles are used to represent the pre-environmental conditions for a Mesoscale Convective Complex (MCC). Several different initial and ambient conditions are used to simulate the effects of vertical shear, the type of precipitation falling through the storm and the radius of the precipitation core. The simulations indicate that the outflows and downdrafts are sensitive to 1) the vertical profile of temperature and humidity, 2) vertical wind shear, 3) low-level inflow speeds, 4) the type of precipitation and 5) the radius of the precipitation shaft. One interesting result of the study relates to the formation and life cycle of the ring vortex associated with the downdraft. When a low-level shear is imposed against the forward outflow boundary the vortex in this region dissipates while the vortex on the rear flank of the storm is enhanced. As the shear in the lower levels is increased, the ring vortex on the front flank of the storm is slower in its downward propagation to the surface from its initiation point. The ring vortex in these simulations always formed in the region where the temperature profile first becomes adiabatic. In the simulations where the radius of the precipitation core is varied it is found that the buoyancy term in the vertical equation of motion is always the key in the calculation of the vertical motion. The results show that the growth rate of the downdraft is slow for large radius and fast for small radius. This is consistent with the theory of scale dependence. |
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| Item Description: | "Major subject: Meteorology." Typescript (photocopy). Vita. |
| Physical Description: | xviii, 154 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |