Photochemical Air Pollution Modeling
275
(EC, 2001). This directive obliges each member state to develop and to implement a
strategic National Program (PTEN) to comply with the emission ceilings until 2010
for the most critical acidifying air pollutants, namely, sulfur dioxide (SO 2 ), nitrogen
oxides (NO x ), non-methane volatile organic compounds (NMVOC), and ammonia
(NH 3 ), responsible for noxious effects on the environment.
In this context, Portugal has developed technical studies aimed at setting up a
reference scenario by 2010 and at evaluating the compliance with the emission ceilings established for this target year. In addition to this reference scenario, high and
low emission reduction scenarios have also been defi ned (IA, 2004a,b,c). Within
this perspective, it is important to evaluate the trends in atmospheric ozone precursor emissions, and consequently predict ozone levels in the near future, taking into
account this kind of national reduction strategy. The objective of this case study was
to evaluate the impact of these national emission reduction scenarios on ozone levels
in continental Portugal and in the main agglomerations of Lisbon and Porto, verifying the fulfi llment of the air quality thresholds for 2010, using atmospheric modeling
techniques.
10.3.1 METHODOLOGY
Photochemical simulations for continental Portugal (not considering Madeira and
the Azores) and for two urban areas were carried out using the comprehensive air
quality model (CAMx) regional CTM with the meteorological forcing coming from
the meteorological model MM5. The analysis of typical synoptical and meteorological conditions associated with ozone exceeding episodes in Portugal for 2001 led to
the selection of the period May 27–29 as the study period.
The air quality photochemical model CAMx (ENVIRON, 2004) is an offl ine
CTM based on the integration of the continuity equation for the concentrations of
several chemical species in each cell of a given 3D grid domain. This model has been
used for several research applications covering short- and long-term photochemical
and aerosol simulations (Soong et al., 2005; Morris et al., 1997). CAMx has also
been applied in sensitivity analysis to grid resolution, chemical mechanisms, and
emissions including source apportionment techniques (Bedogni et al., 2005; Ferreira
et al., 2003; Morris et al., 1998).
The meteorological input variables come from MM5 (Dudhia, 1993), which was
initialized with reanalysis data from the European Centre for Medium Range Weather
Forecasting (ECMWF) with 2.5° of resolution and applied to fi ve domains that make
up a large part of Europe, the Iberian Peninsula, Portugal, Lisbon, and Porto with a
spatial resolution of 90, 30, 10, and 2 km, respectively (see Figure 10.4).
Besides the meteorological input, the CAMx model needs initial and boundary
conditions, emission data, and land-use and topography characterization. In order
to evaluate the impact of the emission reduction scenarios on air quality, numerical
simulations with the CAMx model were performed for continental Portugal and the
urban areas of Porto and Lisbon, fi rst for the 2001 baseline period and then compared with the 2010 scenarios, using the same 2001 meteorological conditions. The
national total emission data for each simulated year (2001 and 2010) were disaggregated according to a top-down methodology (Monteiro et al., 2005b). Therefore,
© 2010 by Taylor and Francis Group, LLC
275
(EC, 2001). This directive obliges each member state to develop and to implement a
strategic National Program (PTEN) to comply with the emission ceilings until 2010
for the most critical acidifying air pollutants, namely, sulfur dioxide (SO 2 ), nitrogen
oxides (NO x ), non-methane volatile organic compounds (NMVOC), and ammonia
(NH 3 ), responsible for noxious effects on the environment.
In this context, Portugal has developed technical studies aimed at setting up a
reference scenario by 2010 and at evaluating the compliance with the emission ceilings established for this target year. In addition to this reference scenario, high and
low emission reduction scenarios have also been defi ned (IA, 2004a,b,c). Within
this perspective, it is important to evaluate the trends in atmospheric ozone precursor emissions, and consequently predict ozone levels in the near future, taking into
account this kind of national reduction strategy. The objective of this case study was
to evaluate the impact of these national emission reduction scenarios on ozone levels
in continental Portugal and in the main agglomerations of Lisbon and Porto, verifying the fulfi llment of the air quality thresholds for 2010, using atmospheric modeling
techniques.
10.3.1 METHODOLOGY
Photochemical simulations for continental Portugal (not considering Madeira and
the Azores) and for two urban areas were carried out using the comprehensive air
quality model (CAMx) regional CTM with the meteorological forcing coming from
the meteorological model MM5. The analysis of typical synoptical and meteorological conditions associated with ozone exceeding episodes in Portugal for 2001 led to
the selection of the period May 27–29 as the study period.
The air quality photochemical model CAMx (ENVIRON, 2004) is an offl ine
CTM based on the integration of the continuity equation for the concentrations of
several chemical species in each cell of a given 3D grid domain. This model has been
used for several research applications covering short- and long-term photochemical
and aerosol simulations (Soong et al., 2005; Morris et al., 1997). CAMx has also
been applied in sensitivity analysis to grid resolution, chemical mechanisms, and
emissions including source apportionment techniques (Bedogni et al., 2005; Ferreira
et al., 2003; Morris et al., 1998).
The meteorological input variables come from MM5 (Dudhia, 1993), which was
initialized with reanalysis data from the European Centre for Medium Range Weather
Forecasting (ECMWF) with 2.5° of resolution and applied to fi ve domains that make
up a large part of Europe, the Iberian Peninsula, Portugal, Lisbon, and Porto with a
spatial resolution of 90, 30, 10, and 2 km, respectively (see Figure 10.4).
Besides the meteorological input, the CAMx model needs initial and boundary
conditions, emission data, and land-use and topography characterization. In order
to evaluate the impact of the emission reduction scenarios on air quality, numerical
simulations with the CAMx model were performed for continental Portugal and the
urban areas of Porto and Lisbon, fi rst for the 2001 baseline period and then compared with the 2010 scenarios, using the same 2001 meteorological conditions. The
national total emission data for each simulated year (2001 and 2010) were disaggregated according to a top-down methodology (Monteiro et al., 2005b). Therefore,
© 2010 by Taylor and Francis Group, LLC