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J. Benavides et al.
on December 2020. In the literature, little evidence of the positive impact of LEZs
on decreasing NO 2 levels has been found in part due to the limited understanding of
diesel emission factors under real-world driving conditions [6]. To evaluate episodic
and structural impact on air quality derived from LEZ implementation, a modelling
system coupling regional to street scales can provide the necessary information of
background pollutant levels and meteorological data to estimate local pollutant concentration gradients using a street-scale dispersion model. In this work, we evaluate
CALIOPE-Urban system that combines CALIOPE [7] with R-LINE [8] adapted to
Barcelona street geometrical conditions and we explore the sensitivity of NO 2 street
concentration levels to a reduction of NO x emissions as a prior step to analyze the
impact of Barcelona LEZ.
27.2 Methodology
27.2.1 CALIOPE Air Quality System
The CALIOPE system integrates the Weather Research and Forecasting meteorological model (WRF), the BSC-CNS in-house High-Elective Resolution Modelling
Emission System (HERMESv2.0; [5]), the Community Multiscale Air Quality Modeling System (CMAQ) and the mineral Dust REgional Atmospheric Model (BSCDREAM8b). The mesoscale system runs over Europe at a 12-km horizontal resolution, Iberian Peninsula at 4-km, and the Barcelona domain at 1-km. CMAQ vertical
levels are collapsed from the 38 WRF levels to 15 layers up to 50 hPa with six layers
falling within the PBL. CMAQ version 5.0.2 with CB05 chemical mechanism and
AERO5 aerosol scheme is used.
27.2.2 CALIOPE-Urban
The combination between CALIOPE and R-LINE, CALIOPE-Urban, requires the
use of CMAQ for background concentration data and WRF for meteorological
inputs. WRF bottom layer over the street of interest is used as boundary conditions for R-LINE local meteorology module. With respect to background concentrations, the upwind urban background scheme is applied. The upwind background
scheme chooses CMAQ grid cell values depending on wind speed and direction.
R-LINE hourly emissions inputs for each road segment are provided by HERMES
that produces specific hourly emissions for each street segment. R-LINE is run using
the numerical integration approach to solve Gaussian dispersion equations and the
Generic Reaction Set (GRS) for NO–NO 2 –O 3 chemical reactions [3]. Receptors are
located at 3 meters (m) above ground level forming a regular grid of 10 m horizon-
J. Benavides et al.
on December 2020. In the literature, little evidence of the positive impact of LEZs
on decreasing NO 2 levels has been found in part due to the limited understanding of
diesel emission factors under real-world driving conditions [6]. To evaluate episodic
and structural impact on air quality derived from LEZ implementation, a modelling
system coupling regional to street scales can provide the necessary information of
background pollutant levels and meteorological data to estimate local pollutant concentration gradients using a street-scale dispersion model. In this work, we evaluate
CALIOPE-Urban system that combines CALIOPE [7] with R-LINE [8] adapted to
Barcelona street geometrical conditions and we explore the sensitivity of NO 2 street
concentration levels to a reduction of NO x emissions as a prior step to analyze the
impact of Barcelona LEZ.
27.2 Methodology
27.2.1 CALIOPE Air Quality System
The CALIOPE system integrates the Weather Research and Forecasting meteorological model (WRF), the BSC-CNS in-house High-Elective Resolution Modelling
Emission System (HERMESv2.0; [5]), the Community Multiscale Air Quality Modeling System (CMAQ) and the mineral Dust REgional Atmospheric Model (BSCDREAM8b). The mesoscale system runs over Europe at a 12-km horizontal resolution, Iberian Peninsula at 4-km, and the Barcelona domain at 1-km. CMAQ vertical
levels are collapsed from the 38 WRF levels to 15 layers up to 50 hPa with six layers
falling within the PBL. CMAQ version 5.0.2 with CB05 chemical mechanism and
AERO5 aerosol scheme is used.
27.2.2 CALIOPE-Urban
The combination between CALIOPE and R-LINE, CALIOPE-Urban, requires the
use of CMAQ for background concentration data and WRF for meteorological
inputs. WRF bottom layer over the street of interest is used as boundary conditions for R-LINE local meteorology module. With respect to background concentrations, the upwind urban background scheme is applied. The upwind background
scheme chooses CMAQ grid cell values depending on wind speed and direction.
R-LINE hourly emissions inputs for each road segment are provided by HERMES
that produces specific hourly emissions for each street segment. R-LINE is run using
the numerical integration approach to solve Gaussian dispersion equations and the
Generic Reaction Set (GRS) for NO–NO 2 –O 3 chemical reactions [3]. Receptors are
located at 3 meters (m) above ground level forming a regular grid of 10 m horizon-