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Abstract
The rapid expansion of urbanization has drastically changed regional landscapes around the globe. While only a small percentage of the Earths surface is covered by cities, more than half of the worlds population resides within their boundaries. Urban climate studies have documented temperature, precipitation, and aerosol anomalies near cities. Consequently, cities are simultaneously vulnerable to and the cause of shifts in climate regimes. Urban climate research, however, has largely ignored the aggregate effects of urban clusters, or multiple adjacent cities, on weather and climate at a regional scale. Research shows that cities may impact atmospheric circulation outside of city boundaries as well as precipitation type during winter weather events. Understanding how and where these impacts are prone to occur is valuable in helping communities prepare for weather events and the development of mitigation strategies during continued growth. This dissertation investigates how urban clusters impact regional climate, particularly how winter precipitation type is modified by cities. The overarching goal is to determine, not only these effects but, whether the current observational network, numerical modeling tools, and postprocessing techniques are viable in assessment of urban-scale processesduring transitional precipitation events. Results show that urban environments increase hydrometeor exposure to above freezing temperatures causing increased melting, mixed precipitation events are more likely to occur within cities than in rural areas, and the existence of nearby, but non-adjacent, cities is a factor in the magnitude of other urban heat islands.