Performance Evaluation of the Empirical Kinetic Modeling Approach (EKMA)
The EKMA is a Lagrangian photochemical air quality simulation model that calculates ozone from its precursors: nonmethane hydrocarbons (NMHC) and nitrogen oxides (NOx). This study evaluated the performance of the EKMA when it is used to estimate the maximum ozone concentration that can occur in an urban area and its environs. The evaluation was conducted using data for five U.S. cities. This paper reports the results for St. Louis, Missouri.
A novel statistical evaluation procedure was developed to measure the accuracy of the EKMA ozone estimates. The accuracy parameter is defined as the ratio of observed to estimated ozone. Associated with this ratio is an accuracy probability, which is defined as the probability that the ratio lies within a predefined percent (e.g., ±20 percent) of unity, a unit value of the ratio denoting perfect agreement between observation and prediction. Equations were derived that express the ratio as a function of NMHC and NOx. The evaluation procedure thus uses NMHC and NOx as inputs to calculate the accuracy probability of the EKMA ozone estimate. The full range of accuracy probabilities associated with the EKMA ozone estimates is displayed in graphical form on the NMHC-NOx plane.
KeywordsShade Area Maximum Daily Temperature Accuracy Probability Photochemical Oxidant Maximum Ozone
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