"Advisors: Dr. Anne Thompson and Dr. George Young."

"Abstract: The recent change in EPA surface ozone regulation, lowering surface ozone daily maximum 8-hour average (MDA8) exceedance threshold from 75 ppbv to 70 ppbv, poses significant challenges to US air quality (AQ) forecasters responsible for MDA8 ozone forecasts. The forecasters, supplied by only a single operational AQ model known as National Air Quality Forecast Capability (NAQFC), end up relying heavily on self-developed tools.  To help US AQ forecasters, this work develops surface ozone MDA8 forecasting tool based solely on statistical methods and standard meteorological parameters from the numerical weather prediction (NWP) models.  The model combines self-organizing map (SOM), a clustering technique, with a stepwise weighted quadratic regression using meteorological variables as predictors for ozone MDA8.  The SOM method identifies different weather regimes, to distinguish between various modes of ozone variability, and groups them according to similarity.  In this way, when a regression is developed for a specific regime, data from the other regimes are also used, with weights based on their similarity to this specific regime.  This approach, regression in SOM (REGiS), yields a distinct model for each regime taking into account both the training cases for that regime and other similar training cases.  To produce probabilistic MDA8 ozone forecasts, REGiS weighs and combines all of the developed regression models based on the weather patterns predicted by a NWP model. REGiS, evaluated with ozone observations over San Joaquin Valley in California, performs best when trained and adjusted separately for an individual AQ station and its corresponding meteorological site."