Surface-level ozone causes serious health impacts in humans and damages crops and terrestrial ecosystems. High concentrations of ozone are due to a combination of photochemistry, dynamics, and background or long range transport of pollutants. As discussed in the NESCAUM report (NESCAUM, 2006), ""Scientific studies have uncovered a rich complexity in the interaction of meteorology and topography with ozone formation and transport."" Different regions have different characteristics, and the situation for the Northeastern United States has been described in the following manner: At nighttime, a temperature inversion forms, isolating ozone above the inversion layer, so it is not chemically destroyed or deposited. Because winds are often much stronger above the inversion layer, this aloft ozone can be transported long distances. The next morning, as the boundary layer breaks up, the aloft ozone can be mixed down to the surface and contribute to rapidly increasing concentrations. We define “nighttime aloft ozone” as the high ozone concentrations that can be found in the region of the atmosphere between the nocturnal boundary layer and the top of the daily mixing layer that serves as an ozone reservoir throughout the night. In polluted environments, the entrainment of nighttime aloft ozone in the morning may be as important as chemical ozone production during the day (Athanassiadis et al., 2002). In national parks close to polluted regions, such as Yosemite and Great Smoky Mountains, the ozone frequently exceeds 90 ppb and overnight transport of ozone substantially contributes to these elevated concentrations (Mueller, 1994; Burley and Ray, 2007). To help protect human health and ecosystems, regional-scale atmospheric chemistry models are used to forecast high ozone events and to design emission control strategies to decrease the frequency and severity of ozone events. Despite the importance of nighttime aloft ozone, regional-scale atmospheric chemistry models do not simulate the surface nighttime ozone concentrations well (Sokhi et al., 2006; O'Neill et al., 2006) and nor do they sufficiently capture the nighttime ozone transport patterns (Gilliland et al., 2008). Fully characterizing the importance of the processes has been hampered by limited measurements of the vertical distribution of ozone and ozone-precursors. The main focus of this proposal is to begin to utilize remote sensing data sets to characterize the impact of nighttime aloft ozone to air quality events. Our specific objectives are: * Characterize nighttime aloft ozone using remote sensing data and sondes. * Evaluate the ability of the Community Multi-scale Air Quality (CMAQ) model and the National Air Quality Forecast Capability (NAQFC) model to capture the nighttime aloft ozone and its relationship to air quality events. * Analyze a set of air quality events and determine the relationship of air quality events to the nighttime aloft ozone. To achieve our objectives, we will utilize the ozone profile data from the NASA Earth Observing System (EOS) Tropospheric Emission Spectrometer (TES) and other sensors, ozonesonde data collected during the Aura mission (IONS), EPA AirNow ground station ozone data, the CMAQ continental-scale air quality model, and the National Air Quality Forecast model. The EOS TES instrument measures in the infrared, allowing it to produce nighttime ozone profiles, unlike other remote sensing ozone measurements. This proposal is a collaborative effort of remote sensing experts, and air quality scientists with knowledge of CMAQ and the NAQFC. Many of the barriers to success in this research area (lack of familiarity between the communities, remote sensing data with appropriate sensitivity, mathematical tools for quantitative comparison of remote sensing measurements and models) have been removed, allowing progress and success of the proposed work. This work is proposed to be conducted as Fundamental Research.