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Mesoscale Adjustments within the Planetary Boundary Layer in Tropical and Extratropical Environments
AuthorFearon, Matthew G.
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A series of three papers comprised the research completed for this dissertation study. Each contribution examined mesoscale processes that occurred within the planetary boundary layer in the context of the chosen avenue of research. The premise of paper one centered on the daytime growth of the convective mixed layer over the continental mid-latitudes for the application of smoke management from wildland fire. An evaluation of the most robust practical technique for mixed-layer height estimation was performed using numerical model simulations and space-based lidar retrievals. Results revealed that daytime mixed-layer growth corresponded with the excitation of the turbulent kinetic energy (TKE) and layer height was best determined where the dissipation of TKE occurred in the vertical. Papers two and three were completed as a two-part series where emphasis was placed on the boundary layer dynamics associated with the precursor environment wherein Hurricane Sandy (October 2012) developed. And although greater attention was paid to the localized mesoscale dynamics, evaluation of the larger-scale influence was also examined across the entire northern hemisphere weeks in advance. Results from two mesoscale model simulations, a control run and no-terrain experiment, show that the precursor environment is highly influential to its developmental fate. In the case of Sandy, the surrounding orography imposed constraints on the environmental mass field such that a low-level curved momentum channel was produced upstream of the incipient disturbance (on its southwestern side) wherein vorticity generation was maximized and wrapped into the vortex inflow region. The latter westerly momentum also converged with a secondary low-level southerly jet feature that emanated into the vortex inflow region. Model results were evaluated against a suite of satellite data including composite brightness imagery, scatterometer surface wind data, space-based lidar retrievals, and Best Track data (on storm track, mean sea level pressure, and maximum tangential wind speed) from the National Hurricane Center database.