In ExternE the air quality is estimated by the use of atmospheric dispersion models.
It is important to note that not only local damages have to be considered -
air pollutants are transformed and transported and cause considerable damage hundreds of kilometres away form the source.
So local, European wide, and north hemispheric modelling is considered in EcoSenseWeb.
Local range analysis:
The Industrial Source Complex Model (ISC) is a Gaussian plume model developed by the US-EPA. The ISC is used for transport modelling of primary air pollutants (SO2, NOx, particulates) on a local scale (100 x 100 kmē around the power plant site). EcoSenseWeb provides a short-term version of the model which uses hourly site specific meteorological data. These data are generated within EcoSenseWeb. The user has only to provide longitude and latitude coordinates (in decimal degree).
The tool used to derive local meteorological data was developed within NEEDS, RS1b, WP1.
Regional range analysis:
The regional range analysis is based on the large EMEP-grid cells (50 km x 50 km) and covers the whole of Europe.
Regional impact assessment is done with regional SR-receptor matrices, i.e. parameterised results of model runs with the EMEP/MSC-West Eulerian dispersion model. These model runs are based on certain emission scenarios (including spatial distribution of different sources) and meteorological conditions. A reduction of each pollutant by 15% for each source of emission within a corresponding sub-region is modelled. Europe is divided into 66 regions, i.e. some larger countries are subdivided into sub-regions.
For a 15% reduction of an airborne pollutant (e.g. NOx) within a country / sub-region of Europe (e.g. Belgium) based on meteorological conditions
(e.g. in the year 2000) and background emissions of e.g., the year 2010, a model run was performed by MET.NO.
The result is a matrix covering the resulting concentration of different pollutants in each of the 50 x 50 km2 grid cell of the EMEP grid.
This matrix contains the results in terms of concentrations of a primary (NOx) or secondary (nitrates and ozone, increased sulphates, etc.) air pollutants on
the 50 km x 50 km EMEP grid. The chemical reactions and interactions are quite complex.
For example, a reduction of NOx emissions leaves more background NH3 for reaction with background SO2, and therefore, increases the concentration of sulphates, etc.
Based on meteorological years 1996, 1997, 1998 and 2000 average results have been derived representing typical conditions of the present. The year 2003 was an exceptional warm year in Europe. Therefore, the results based on meteorological year 2003 are used to estimate future conditions, reflecting the influence of climate change.
Hemispheric range analysis:
With introduction of the North Hemispheric range analysis within NEEDS the range of analysis has been expanded. The concept of hemispheric range analysis results from the need of performing an estimation of the intercontinental influence on concentrations of primary and secondary airborne pollutants. Analysis is based on corresponding EMEP/MSC-West Eulerian dispersion model runs which produced source-receptor relationships at the hemispheric scales for 4 regions of the Northern Hemisphere.
The emissions data are based on Edgar (2000) data and within the EMEP area EMEP emissions are used. Meteorological input data correspond to the year 2001.
The methodology is described in more detail in the Technical Paper (MET.NO TP1.1).
The Northern Hemisphere has been divided into four areas:
Far East (FE), Middle East (ME), North America (NA), Europe (EU).
Temporarily, a fifth region (WEU) has been included, where Russia has been excluded from Europe.
The effect of reductions of six different pollutants (NOx, SOx, NMVOC, NH3, PM2.5 and PMco) has been computed.
Each scenario reduces one pollutant from one area by 15%.
Local/Regional and Local/Regional/Hemispheric calculations:
The regional range area overlaps the local range are and the hemispheric range area overlaps the regional range are. Therefore local and regional impacts must not be added up
to calculate the total impact. A routine has been implemented to calculate the total impacts, avoiding a double counting and taking into account the more
detailed results derived on the local and regional range.