... 321 Time( Day)Concntration(ppm)Fig. 1: Time series plots of selected air pollutions (solid line) and fitted regression curves (dashed lines)Concentration (ppm) Time (Day) Time (Day) Time (Day) Time (Day) Time (Day)Concentration ... (SAPI) time series were also calculated to compare fluctuation of different time series with different levels. SAPI time series indicated that NO and NO2, CH4 and non-CH4 have similar time ... associated with air quality datathrough time (Salcedo, et al., 1999). Time series analysis A time series is a set of observations that arearranged chronologically. In time series analysis, theorder...