Prediction of surface ozone exceedance days using PCA with a non-parametric T 2 control limit.

Abstract: It is noted that the data for ozone precursors and meteorological variables exhibit non-normal distributions. Thus, to detect surface ozone exceedance days, we propose a principal component analysis (PCA) model with a non-parametric T 2 control chart. The input variables include concentrations of ozone (O3), nitrogen oxide (NO), and nitrogen dioxide (NO2), wind speed (WS), relative humidity (RH), solar radiation (SR), surface and aloft temperatures (T). In addition, process variation indicators of meteorological factors are proposed to capture dynamic weather patterns. Ozone precursors and meteorological measurements of non-exceedance days during extended summers (May 16th–Oct. 15th) from 2000 to 2007, which include 1153days, are used to train a PCA model for the Livermore Valley, CA. Data of ozone exceedance days for the same period are used for validation of the model. Summer data from 2008 to 2009, which include 11 exceedance days, are used to test this prediction model. An ozone exceedance day is triggered when any T 2 value of this day exceeds the non-parametric T 2 control limit. Compared to a conventional PCA with a Hotelling T 2 control chart, the true prediction rate (TPR) of ozone exceedance days using this PCA model with a non-parametric T 2 control chart is increased from 45.45% to 72.73%. When process variation indicators (PVIs) are introduced into the PCA model with a non-parametric T 2 control chart, the TPR of ozone exceedance days is shown to increase to 100%. [Copyright &y& Elsevier]