Collaborative Research: Persistent Wintertime Temperature Inversions in the Salt Lake Basin

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A three-year research project will be conducted to investigate processes leading to the formation, maintenance and destruction of persistent, multi-day, mid-winter temperature inversions or cold-air pools that form in the Salt Lake basin (SLB). These persistent inversions occur frequently as well in other regions throughout the western US and throughout the world, and their initiation and breakup are quite difficult to forecast. Air pollution can reach unacceptably high levels during persistent inversions in urban basins, and when the inversion breaks the breakup can carry pollution vertically to produce regional-scale air pollution and climate impacts. Because of poor mixing, fog and stratus can build up in the inversion leading to hazardous episodes of persistent freezing rain, drizzle or fog and interfering with ground transportation and aviation.The objectives of the project are to 1) identify the meteorological processes that lead to buildup, maintenance and breakup of persistent inversions, 2) determine the consequences of these processes on air pollution transport and diffusion in urban basins, and 3) determine how meteorological models can be improved to provide more accurate simulations of such persistent inversions.The project includes observations, analysis, and modeling. The initial focus will be modeling of an event in the winter of 2000-2001 using existing meteorological data. The analyses of this recent event study will identify the key physical mechanisms leading to persistent inversion formation and destruction in this case.A field experiment will be conducted in the SLB from 1 Dec 2010 to 7 Feb 2011 to obtain the detailed meteorological data on several more cases needed for further model simulations and analyses. A mesoscale meteorological model will be used to interpret the observations, verify hypotheses, provide further insight into physical mechanisms, and evaluate the air pollution implications of the inversion processes. The simulations will take account of the often-observed fog and stratiform clouds that form and dissipate within the SLB inversions.Intellectual Merit: The project will advance knowledge and understanding of the physical processes that affect persistent inversions. This increase in knowledge is expected to lead to improvements in models and, ultimately, in weather forecasts for the western U.S. and throughout the world. The work uses innovative approaches, employs conceptual models of relevant physical processes resulting from earlier research, and uses a combination of analyses of prior data and collection of new data and numerical modeling to gain understanding.Broader Impacts: Broader societal impacts are promoted through the integration of the research into university teaching, through the support of undergraduate and graduate students and through the promotion of investigator/student diversity. Project results will be widely disseminated through peer-reviewed scientific publications and presentations. The results have potential benefits to society through improved understanding of cold pools with potential applications for better understanding air pollution dispersion, weather forecasting and climate.