Screening for High Emission Reduction Potential on Air

SHERPA is an integrated assessment tool, developed since June 2016 by JRC. It aims at supporting local and regional authorities in preparing air quality plans and assessing their impacts on concentration levels.

The tool is based on simplified emission-concentration relationships that allow for a rapid screening of the impacts of emission reductions plans in any European region, or set of regions.

SHERPA can be used for the formulation, implementation and evaluation of EU policies, legislation and other measures related to air quality. In particular, it can be used in the frame of Impact Assessment procedures to examine potential environmental consequences of perspective regional air quality policies, and evaluate options to improve the effectiveness of the EU action.

SHERPA delivers information on

1. the potential for abatement strategies in a given region/city/country,
2. source allocation in terms of either emission precursor (e.g. Primary Particulate, NOx, …) or activity sector (e.g. transport, energy…) and
3. the key neighboring regions/countries with whom to collaborate to increase the efficiency of air quality plans.

SHERPA currently covers the following pollutants: NO2, PM10 and PM2.5 (yearly averages). For PM2.5, it also computes related health impacts (i.e. premature deaths, Years of Lost Life). Since a full chemistry transport model (CTM) cannot be used online to determine the relationship between emissions and resulting concentrations, simplified relationships are constructed on the basis of pre-elaborated data based on a set of CTM calculations.

Main components:   

• Source allocation module: calculates the contribution of any emission sector/precursor to the concentration levels at one given location
• Governance analysis: calculates the contribution of each region in Europe to the concentration observed at one location for a given sector/precursor 
• Scenario: calculates the impact of a given emission scenario (specified in terms of sector/precursor relative reductions) on concentrations.
• Atlas module: it allows to reproduce the results as presented in the "Urban PM2.5 Air Quality in European Cities", in particular the source of pollution for 150 main cities in Europe.

SHERPA is configured and released with a default dataset covering all Europe. It can however be fed by user data for the same European domain or for a smaller domain, provided the following input data are made available:

• gridded emission inventory,
• emission-concentration relationships (based on a full air quality model)
• shape files defining the areas of interest where emission reductions might take place. 

SHERPA is based on the assumption that emissions and concentrations are linearly related, an assumption that has been shown to be valid for yearly averaged concentrations. SHERPA is therefore limited to the analysis of impacts for yearly concentrations.

The emission-concentrations relationships can be obtained through the use of a CTM (Chemistry transport model) such as CHIMERE.