Graduate Thesis Or Dissertation
 

Diagnostic modeling study of a severe narrow cold-frontal rainband

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/r781wj930

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  • A diagnostic modeling study of the cloud and precipitation processes, and also frontogenesis have been analyzed in a severe narrow cold-frontal rainband with the aid of a three-dimensional, diagnostic cloud model. The results of the model simulations indicate that the heavy precipitation just behind the surface cold front was associated with a low-level warm rain process driven by the severe prefrontal updraft. The precipitation well behind the leading edge of cold front resulted from the melting of graupel. The sensitivity studies for the rain water distribution indicated that the Analytical Gamma distribution may be a more suitable functional fit for the raindrop distribution as compared with the Marshall-Palmer distribution. The differential heating due to microphysical processes (condensation and evaporation) at the leading edge of the surface cold frontal region facilitated the required density contrast across the front and thus maintained the propagation of the density current. The leading edge of the cold front was also characterized by frontogenesis for levels above 0.9 kin and frontolysis just ahead and immediately behind the cold front. The low level frontolysis indicated that buoyancy effects were almost negligible at the leading edge of the cold front. Instead the upward motion was created by mechanical lifting (pressure effects). The frontogenetical effects due to diabatic heating were quite important at the 1.2 - 2 km levels where the peak updraft occurred.
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