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|Title:||The Numerical Simulation of Orographic Storms (Wales, Seeder-Feeder Mechanism, Bergeron)|
|Author(s):||Bradley, Michael Morgan|
|Department / Program:||Atmospheric Sciences|
|Degree Granting Institution:||University of Illinois at Urbana-Champaign|
|Subject(s):||Physics, Atmospheric Science|
|Abstract:||Recent observational studies of winter storms over the Glamorgan Hills of south Wales (Browning et al., 1974, and Hill et al., 1981) have confirmed the importance of the seeder-feeder mechanism of orographic precipitation enhancement, proposed by Bergeron (1965). However, the latter study also indicated that the sensitivity of the enhancement to the low-level wind speed is much greater than predicted by the seeder-feeder model of Bader and Roach (1977), which simulates only the microphysical processes.
A new, dynamic mountain model was used to investigate the hypothesis that mountain wave effects were responsible for this increased wind speed sensitivity. The model, which evolved from the cloud model of Klemp and Wilhelmson (1978), is formulated in terrain-following coordinates. In addition to representing convective and stratiform cloud processes, the model is also capable of accurately simulating moderately nonlinear mountain waves, and is suitable for studying many aspects of orographic storms.
The simulations show that orographic clouds significantly alter the airflow over hills and, conversely, that mountain waves strongly influence the moist processes. Wind speed, wind shear, atmospheric stability, and relative humidity are all important factors in the complex scale interactions which occur during orographic storms. The results strongly support the hypothesis that certain mountain wave effects greatly increase the wind speed sensitivity of the Bergeron seeder-feeder mechanism.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.
|Date Available in IDEALS:||2014-12-16|