Date of Award
Master of Science
Geological and Atmospheric Sciences
Tsing-Chang (Mike) Chen
Gene S. Takle
The surface cold front is an important phenomenon that influences our weather on a regular basis. Cold fronts have the ability to influence decision-making regarding the growing wind energy industry in Iowa. Despite the abundance of literature and attention directed towards the study of cold fronts, areas of improvement remain in the numerical modeling of cold fronts. One area of improvement lies in the dynamical distinction between the non-outflow boundary cold front (NOCF) and outflow boundary cold front (OCF). Historically, outflow boundaries have been defined as a cold column of air formed by evaporative cooling that reaches the ground and spreads out horizontally. This definition does not explain why some cold fronts with associated precipitation do not produce an outflow boundary. An additional mechanism must exist that can trigger the release of an outflow boundary from a cold front. Comparative analysis of the distinct synoptic and dynamic features of the NOCF compared to an OCF event identified several potential trigger mechanisms, including a low pressure trough that weakened after frontal occlusion and an upper level dipole structure of geopotential height. Thermodynamic and vorticity budget analyses were conducted to explain the important synoptic features for the NOCF and OCF events. The location of adiabatic warming differed between the two events and vortex stretching was more prominent in the OCF case than in the NOCF case. The ability of the NAM model to accurately forecast the NOCF event was assessed, with an emphasis on how wind power operators may use this information to better predict wind surging over Iowa. Results indicated that the NAM model has trouble predicting both the location and magnitude of the wind surge associated with the NOCF. An expansion of this study to include a wind surge forecast advisory is discussed.
Amanda Suzanne Black
Black, Amanda Suzanne, "An investigation of summer season cold fronts unassociated with an outflow boundary" (2014). Graduate Theses and Dissertations. 14092.