Orographic Effects on Cold Fronts

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The strength, movement, and associated precipitation of fronts traversing orographic features can be significantly affected by the terrain. Dr. Knight will continue his studies of frontal inter- action with topography via two approaches. A two-dimensional numerical model based on the primitive equations of meteorology will be used to calculate the suite of physical processes involved in the interaction. The model cold front will be formed by the shear flow induced by an evolving non-linear baroclinic Eady wave (the theoretical analogue of a developing midlatitude cyclone). The effect of varying mountain sizes and atmospheric stabilities will be simulated, in both the presence and absence of atmospheric moisture. Under the second approach, the model's simulations will guide the observational analysis of case studies of cold fronts crossing the Appalachians. Observed fronts that are significantly affected by the mountains will be compared with those that are not. In addition to elucidating aspects of the interaction, the case studies will provide a partial check on the verisimilitude of the model simulations. Better understanding of the interaction may lead to improved predictions of precipitation in mountainous terrain, a key aid in water resource management.