In this section you can consult the answers to questions about the Air Quality Modelling Network.
Q. How can I find the appropriate air dispersion model?
A. The Model Tool Guider provides guidance to any model user in the selection of the appropriate model for his application.
Q - Why should the receptors no be more than 10 meters form the kerbside? This distance should be applied in all roadways, even highways, in the rural environment? This should be considered only when we are estimating the impact of the road, or even when the main project is other source?
A - The requirement that a 'traffic monitoring station' be no more than 10 m from the road is in the AQ Directive itself (Annex III.C). It should be noted that the Directive applies basically everywhere people have activities, including on the kerbside. The maximum distance is to ensure that the monitoring, and eventual modelling, represents a kerbside concentration. If there is no access to the kerbside on a road and nobody lives near by (e.g. rural motorway) then this does not need to be assessed (Annex III.A.2).
Q - The Relative Directive Error formula can only be applied to the areas with monitoring points reporting exceedances? And in the other situations, what should we do?
A - The Relative Directive Error can be applied when there are no exceedances because it uses the 'closest' values to the limit value. If these are less than the limit value then the erorr will also normally be less. In this case you will be assessing the uncertainty of the maximum values, compared to the limit value. Note here that the intention of the Directive is to have an uncertainty estimate at the limit value (i.e. it is not so concerned if there is high uncertainty at very low or very high concentrations because that will not affect whether there is an exceedance or not.)
Q - Regarding the point 3.6.4, in the case of the study domain having more than one classification of stations, how can we define the modelling scale? And, how should we make the correspondence between model scale and each type of station?
A - The most important point here is that the model must has a similar spatial representativeness as the monitoring station in order to compare the two. i.e. you cannot assess/validate a model against an observation which has a different spatial representativeness. That is the case when comparing a model to observations. For modelling in general you clearly cannot use a 2km gridded model to represent the concentrations next to a trafficked street. The conclusions would be completely wrong. In regard to the second part of your question, as stated this is an activity of FAIRMODE. Rule of thumb says though that a traffic station requires a model with 1 - 10 m resolution, an urban background station, 1 - 3 km resolution, and a rural background station 5 - 25 km resolution. There is currently no fixed definition of this, which is why FAIRMODE (WG2-SG1) is looking into this aspect.
Q. In the FAIRMODE document "Guide on modelling Nitrogen Dioxide (NO2) for air quality assessment and planning relevant to the European Air Quality Directive" the model CALPUFF is not listed. I wanted to ask if CALPUFF is not accepted for NO2-air quality management in Europe or can we use it also in the future.
A. The list of models in the NO2 Guidance document are only examples and in no way exclude any non-listed models. Any model that has been shown to fulfill the quality objectives in the AQ Directive may be used. It is highly recommended that validation be made by yourself in the environment for which you are applying the model, to guarantee that the model is being used correctly for your application.
Q. The indicator SOMOx is not contained in the AQ Directive (EC, 2008). Is this indicator still retained valid for human health? How it should be calculated? Similar with AOT40? Same proportion of valid data and same adjustment for missing data? (Annex VII of Directive)
A. SOMO00 and SOMO35 are both ozone health indicators, as apposed to AOT40 that is an eco-system indicator. SOMOxx is not included in the Directive as an indicator and so there are no related rules for data coverage, nor any requirements for using reporting. This indicator is however recommended by the world health organisation (WHO) as a suitable health indicator. Perhaps this indicator may be used in the future. You can find the definition for SOMO35 (and AOT40) at: 'http://www.emep.int/SR_data/definitions.pdf'
Q. In the “Guidance on the use of models for the European Air Quality Directive”, what means “-” in Table 6? Model uncertainties does not exist, can be any value or is not yet defined?
A. Model uncertainties indicated by a '-' means that it is not relevant because there are no limit values associated with that time resolution (e.g. there is no limit value for hourly Benzene concentrations, only annual)
Q. How to put together for ozone, the requirements of Annex 1 with Annex VII? For example, for calculating the ozone annual mean can be usde monitoring stations (fixed measurements) with 75% of minimum data capture instead of 90% for summer? This is the proportion of valid data required in Annex VII.
A. Ozone is not covered by Annex I. Annex VII is relevant for ozone only.
Q. In the chapter 7 of the EEA Technical Report: “The application of models under the European Union's Air Quality Directive: A technical reference guide” (No 10/2011), I can’t find Table 9 referred at subchapter 7.2 page 49.
A. 'Table 9' should read 'Table 4.3' which lists a large number of web portals, including air quality forecasts. This is a typographical error in the document.