C. Borrego*, O. Tchepel*, N. Barros*, M. Lopes*, M. Conceição*, M.J.Valinhas*, A.I.Miranda* and S. Lemos**
* Dep. of Environment and Planning, University of Aveiro, 3810
Aveiro, PORTUGAL
**Institute of Environment and Development, Campus Universitario,
3810, Aveiro, Portugal
The activity developed under the EXP working group was the data processing of results obtained from the field campaign LisbEx97, on the Lisbon Region. These processing included the preparation of meteorological, air quality and emissions databases.
Under VAL working group the main actions were related to the analysis of the data obtained from LisbEx97 and long-term data for the same region. A statistical analysis of long-term meteorological and air quality data was performed, as well as time and spatial variation analysis of data from the field campaign. Other line of work, which is described in more detail on the following items of this report, was the development of data processing methodologies in order to establish a specific emission inventory with high temporal and spatial resolution.
The other activity performed during the year was the linkage between
a Gaussian model and a photochemical model with the CBM-IV mechanism, as
a contribution to INT working group.
The generation of an emission inventory for Lisbon Region is based on
two different approaches: a top-down approach for disaggregation of CORINAIR
inventory, and a bottom-up estimation considering emission factors and
a local data set *Borrego, 1998*. These methodologies were applied to road
traffic emissions. Validation of emissions inventory was performed by inter-comparison
of results obtained by different approaches.
As a next step, population data were used as a criteria for downscaling
of emissions to sub-municipal level ("freguesia"). This data was obtained
from Census 91 of the National Institute of Statistics.
Annual emissions have been downscaled to daily emissions, considering
a Summer period between April and September (183 days) and a Winter period
between October and March (182 days). Those daily emissions have also been
broken down to hourly emissions, assuming that the diurnal period corresponds
to 16 hours and the nocturnal period to 8 hours.
In the scope of this work road traffic hot emissions have been estimated for four vehicle categories: light-duty gasoline vehicles (or passengers cars), light-duty diesel vehicles, heavy-duty vehicles and two-wheeled vehicles. A distinction was also made concerning driving modes. Three modes were considered: urban, rural and highway.
Main roads were processed as line sources and their emissions were calculated
on the basis of emission factors, mean daily traffic and road length, according
to the following equation:
where: E i – daily emission of pollutant i for road segment; eij - emission factor for pollutant i and vehicle type j; DMT - daily mean traffic; L - road segment length.
Highway emission factors have been applied for highways, principal and complementary itineraries. For other roads rural emission factors were applied. Data related to the DMT from 57 measurement points were considered.
A Geographical Information System was used for road segments length calculation. Line sources have been subdivided, taking into account the existing crossroads. Traffic data applied to each segment resulted from measurements along each segment or, in its absence, along the nearest one.
The results obtained by the application of this methodology are presented
on figure 1. The figure shows the considered line sources, the measurements
points and the NOx emission rate (kg/km) for a typical summer day for each
road.
Daily pollutants emissions associated to main roads outside the city were aggregated for each NUT III and compared with the emissions from CORINAIR. Emissions estimated for line sources do not represent all traffic emissions and, therefore, only the magnitude of the data should be compared.
There are no sufficient traffic data to apply the bottom-up approach
for the entire city. Therefore only two "freguesias" were selected. Comparison
of the obtained emission data with disaggregated CORINAIR inventory indicates
that emissions for this area are underestimated.
Actions for 1999 include the definition of model scales and overlapping
grid extension, the definition of parameters to exchange between scales
and the development of the linkage process. This linkage will consist in
a two-way transfer information, using a complete exchange of physical variables.
Another line of work will be the processing of data obtained during a field
campaign, to be used for model validation, and wind tunnel experiments
planned for the evaluation of model performance in describing flow and
dispersion over complex geometry, such as street canyons.
Borrego C., N. Barros, M.Lopes, M. Conceição, M.J Valinhas,
O. Tchepel, C. Ferreira, M. Coutinho and S. Lemos – Emission inventory
for simulation and validation of mesoscale models. In: EUROTRAC CORINAIR90
- Inventario Nacional de Emissões Atmosféricas,
Lisboa, 1994.