Coastal zones of the United States are crucially important to many aspects of society. More than half of the United States population lives within 80 km of a coastline and greater than 40 million people reside in the Great Lakes region. Great Lakes lake breezes, which occur most often during the spring and summer months, can have large economic, societal, and climatic impacts on coastal regions. Lake-breeze circulations can significantly modify the near coastal environments by providing cooler temperatures, affecting the development of severe thunderstorms, influencing precipitation amounts and locations, and altering air pollution concentrations and transport. Despite considerable research on lake breezes, and to a lesser amount on lake-cooled, stable marine boundary layers, limited fundamental scientific understanding of several important areas remain. <br/><br/>A number of numerical modeling and laboratory studies suggest that urban areas have large impacts on lake-breeze (or similar sea-breeze) circulations, generally resulting in a decrease in inland movement after the lake-breeze front has reached the urban center. At present, there exists very limited observational information on how sea- and lake-breezes typically move in the vicinity of near-shore urban areas as compared to non-urban areas. A preliminary investigation of lake-breeze frontal movement through two urban areas in the Great Lakes suggests that the expected decrease in inland movement occurs infrequently. This research seeks to determine the variability of lake-breeze movement in these areas and examine the environmental conditions that contribute to the spatial and temporal variations. <br/><br/>There has been recent interest within the meteorological community in examining and understanding the connections between mesoscale systems and climate variability. Great Lakes lake breezes provide an exceptional opportunity to examine this issue. Past investigations of lake-breeze occurrence have examined a limited number of locations in the Great Lakes region over varying timescales. These studies have provided important, but incomplete, information about the spatial and temporal variability of lake breezes. This research seeks to quantify the inter-annual, intra-seasonal, and spatial variations in Great Lakes lake-breeze occurrence and determine their impact on near-shore climate conditions. <br/><br/>Few studies have examined the influence of the warm-season marine boundary layers on convective systems and the precipitation distribution in the Great Lakes region. In fact, the forecasting community continues to assert that one of the most significant summer forecast challenges in the Great Lakes region is the impact, if any, that the marine layer will have on an existing convective system as it crosses a lake. This research seeks to address the gap of knowledge on this issue by understanding the relationship between the evolution of convective systems and marine layer stability and environmental conditions.<br/><br/>Intellectual Merit: Results of the studies will provide new insight into several areas of limited and often conflicting scientific understanding: (a) the influence of urban areas on lake-breeze fronts and the impact of environmental conditions on the lake breeze response to urban areas, (b) the inter-annual, intra-seasonal, and spatial variability of lake breezes and their influence on coastal climate conditions, and (c) the interaction of convective systems with lake-cooled marine boundary layers. These studies will address several fundamental aspects of lake breezes and significantly contribute to the understanding of the impact the Great Lakes have on coastal urban areas, severe weather and precipitation systems, and regional climate conditions. <br/><br/>Broader Impacts: Results of the studies will provide an enhanced understanding of coastal meteorology which affects a host of activities related to commerce, industry, transportation, health, safety, recreation, and national defense. As recently recommended to the larger atmospheric science community, the research will examine air-land interactions, the effects of land-sea breezes, and the climatology of mesoscale systems through the use of observational data subsequently allowing for improved evaluation of regional climate simulations. In addition, the research will notably contribute to benefiting the next generation of scientists. Undergraduate students will be involved through participation in the established summer research program at Hobart and William Smith Colleges. Graduate students will benefit by active participation in a successful research program at the University of Illinois and Illinois State Water Survey. Results will be widely communicated to the scientific community through journal articles and conference presentations and to the operational forecast and air quality communities through regional workshops and presentations.
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