2.3.3. Tropospheric ozone formation (O3)
Traditionally, O3 is a difficult pollutant to deal with due to the
fact that it is not emitted directly, but rather formed from emissions
of other substance. Moreover, the emission-concentration
response of O3 presents important non-linearities, especially
with respect to the emissions of NOx (Rypdal et al., 2005; Amann
et al., 2011). To deal with these issues, AERIS calculates O3
through a non-linear conversion module that correlates the
resulting NO2 concentrations after measures (expressed as the
annual mean concentration of NO2 calculated with Eq. (2)) and
the VOC emissions with the ambient O3 concentration (Carnevale
et al., 2007). The expression for estimating the concentrations of
O3 was adapted from Guariso et al. (2004) and verified with the
use of a surface-regression tool in MATLAB (sftool). The
regression coefficients were calculated following a response
surface methodology according to Chi et al. (2012). Its general
form is shown in Eq. (6), which is subject to the results calculated
with Eq. (7):