The development and application of atmospheric modeling systems to determine the environmental impact of regional scale and local emissions on complex mountain terrain and coastal-urban areas

This dissertation details the development and application of advanced numerical simulation methods in complex mountain terrains (the Lake Tahoe basin, CA-NV) and coastal-urban (San Diego, CA) areas to address the air quality impacts on the environment. In the first phase of the study, multiple land use and land cover scenarios were developed to assess the environmental impact from future emissions in the fast growing urban area of northern San Diego, CA. Based on a novel assessment method known as alternative futures, the employed methodology combined advanced interactive atmospheric chemistry modeling system coupled with a GIS (Geographical Information System) framework. Through a series of simulations, the most beneficial future growth pattern that will bear the same number of population with the least harm on the environment was determined. The tool developed as part of this work appears to be very successful and effective in response to the need to design sustainable environments.; In the second phase of the study, we investigated the sources of nitric acid (HNO3) in the Lake Tahoe basin, located in the Sierra Nevada mountains on the border of California and Nevada. Lake Tahoe has been experiencing declining water clarity over the last few decades. This eutrophication has been attributed to the excess nutrient and sediment loading to the lake. Previous studies have found atmospheric nitrogen (N) deposition to be the predominant path of total N input, and that HNO3 was the major N-containing gas in the basin. In order to develop an effective strategy to reduce N deposition, there is a need to determine the sources of atmospheric N. The simulation results indicated that for an observed high concentration event, total predicted HNO3 concentrations accounted for 81% of the observed HNO 3 concentrations, and local emission sources comprised approximately 70% of the total predictions. In addition, the cause of elevated levels of ambient HNO3 concentrations in the basin is closely related to the meteorological conditions that emerge from the development of terrain-induced local flows. These results indicate that control of in-basin sources of N will be the most effective approach for reducing N deposition in the Lake Tahoe basin.