P. Thunis

Effect of Sea Breeze on Air Pollution in the Greater Athens Area. Part I: Numerical Simulations and Field Observations

Abstract Numerical simulations compared with field measurements are used to explain the effect of sea breezes on photochemical smog episodes in Athens during the Mediterranean Campaign of Photochemical Tracers on 12–14 September 1994. The numerical simulations, performed using a nonhydrostatic vorticity mesoscale model coupled to the Lurmann–Carter–Coyner photochemical module, are compared with ground-based lidar and aircraft measurements. The current analysis shows that the three selected days include the two main summertime flow patterns characteristic of the Athens peninsula, each of which lead to significantly different pollution amounts. On 12 and 13 September, a strong, northerly synoptic wind reduces the inland penetration of the sea breeze so that ozone concentrations within the greater Athens area remained low. In contrast, the weaker synoptic forcing on 14 September allowed the development of sea breezes over the whole peninsula and high ozone concentrations were found north and east of the city...

An integrated assessment tool to define effective air quality policies at regional scale

In this paper, the Integrated Assessment of air quality is dealt with at regional scale. First the paper describes the main challenges to tackle current air pollution control, including economic aspects. Then it proposes a novel approach to manage the problem, presenting its mathematical formalization and describing its practical implementation into the Regional Integrated Assessment Tool (RIAT). The main features of the software system are described and some preliminary results on a domain in Northern Italy are illustrated. The novel features in RIAT are then compared to the state-of-the-art in integrated assessment of air quality, for example the ability to handle nonlinearities (instead of the usual linear approach) and the multi-objective framework (alternative to cost-effectiveness and scenario analysis). Then the lessons learned during the RIAT implementation are discussed, focusing on the locality, flexibility and openness of the tool. Finally the areas for further development of air quality integrated assessment are highlighted, with a focus on sensitivity analysis, structural and non technical measures, and the application of parallel computing concepts.

Effect of Sea Breeze on Air Pollution in the Greater Athens Area. Part II: Analysis of Different Emission Scenarios

Abstract The Mediterranean Campaign of Photochemical Tracers–Transport and Chemical Evolution that took place in the greater Athens area from 20 August to 20 September 1994 has confirmed the role of sea-breeze circulation in photochemical smog episodes that had been suggested already by a number of experiments and numerical studies. The meteorological and photochemical modeling of this campaign were discussed in Part I. Part II focuses on the study of the 14 September photochemical smog event associated with a sea-breeze circulation. The objective of the study is to identify and to understand better the nonlinear processes that produce high ozone concentrations. In particular, the effect of land and sea breezes is investigated by isolating the effect of nighttime and daytime emissions on ozone concentrations. The same principle then is used to isolate the effect on ozone concentrations of the two main sources of emissions in the greater Athens area: the industrial area around Elefsis and the Athens urban ...

A tool to evaluate air quality model performances in regulatory applications

This paper describes the details of the DELTA Tool and Benchmarking service for air quality models, recently developed in the framework of FAIRMODE (Forum for Air Quality Modelling in Europe). One of the main objectives of the FAIRMODE activities is the development of a procedure for the evaluation and benchmarking of air quality modelling applications for regulatory purposes. The DELTA Tool is a specific software which provides summary statistics (i.e. BIAS, RMSE, correlation coefficient) as well as scatter-plots, time series plots, Taylor, Target and other diagrams providing an overview of the quality of model results with respect to monitored data. Moreover, the benchmarking service implemented in DELTA produces summary reports containing performance indicators related to a given model application in the frame of the EU Air Quality Directive (AQD, 2008). This work describes the structure of the DELTA tool and template for reporting model performances. Some examples of application are also briefly presented.

Is regional air quality model diversity representative of uncertainty for ozone simulation

We examine whether seven state-of-the-art European regional air quality models provide daily ensembles of predicted ozone maxima that encompass observations. Using tools borrowed from the evaluation of ensemble weather forecasting, we analyze statistics of simulated ensembles of ozone daily maxima over an entire summer season. Although the model ensemble overestimates ozone, the distribution of simulated concentrations is representative of the uncertainty. The spread of simulations is due to random fluctuations resulting from differences in model formulations and input data, but also to the spread between individual model systematic biases. The ensemble average skill increases as the spread decreases. The skill of the ensemble in giving probabilistic predictions of threshold exceedances is also demonstrated. These results allow for optimism about the ability of this ensemble to simulate the uncertainty of the impact of emission control scenarios.

The European Nitrogen Assessment: Atmospheric transport and deposition of reactive nitrogen in Europe

Approaches Modelling provides a way of estimating atmospheric transport and deposition of N • r at the European scale. A description of the diff erent model types is provided. Current deposition estimates from models are compared with observations from European air chemistry monitoring networks. • Th e main focus of the chapter is at the European scale; however, both local variability and and intercontinental N • r transfers are also addressed.

A new approach to design source-receptor relationships for air quality modelling

Air quality models are often used to simulate how emission scenarios influence the concentration of primary as well as secondary pollutants in the atmosphere. In some cases, it is necessary to replace these air quality models with source-receptor relationships, to mimic in a faster way the link between emissions and concentrations. Source-receptor relationships are therefore also used in Integrated Assessment Models, when scenario responses need to be known in very short time. The objective of this work is to present a novel approach to design a source-receptor relationship for air quality modeling. Overall the proposed approach is shown to significantly reduce the number of simulations required for the training step and to bring flexibility in terms of emission source definition. A regional domain application is also presented, to test the performances of the proposed approach. A novel approach to design source-receptor relationships for air quality is proposed.It needs a small number of simulations to be implemented.It also brings flexibility in terms of application in Integrated Assessment Models.A case study on a regional domain is presented.

Exploring trade-offs between air pollutants through an Integrated Assessment Model.

When designing air pollution reduction policies, regional decision makers face a limited budget to choose the most efficient measures which will have impacts on several pollutants in different ways. RIAT+ is a regional integrated assessment tool that supports the policy maker in this selection of the optimal emission reduction technologies, to improve air quality at minimum costs. In this paper, this tool is formalized and applied to the specific case of a French region (Alsace), to illustrate how focusing on one single pollutant may exacerbate problems related to other pollutants, on top of conflicts related to budget allocation. In our case, results are shown for possible trade-offs between NO2 and O3 control policies. The paper suggests an approach to prioritize policy maker objectives when planning air pollution policies at regional scale.

A novel approach to screen and compare emission inventories.

A methodology is proposed to support the evaluation and comparison of different types of emission inventories. The strengths and weaknesses of the methodology are presented and discussed based on an example. The approach results in a “diamond” diagram useful to flag out anomalous behaviors in the emission inventories and to get insight in possible explanations. In particular, the “diamond” diagram is shown to provide meaningful information in terms of: discrepancies between the total emissions reported by macro-sector and pollutant, contribution of each macro-sector to the total amount of emissions released by pollutant, and the identification and quantification of the different factors causing the discrepancies between total emissions. A practical example in Barcelona is used for testing and to provide relevant information for the analyzed emission datasets. The tests show the capability of the proposed methodology to flag inconsistencies in the existing inventories. The proposed methodology system may be useful for regional and urban inventory developers as an initial evaluation of the consistency of their inventories.

Performance criteria for the benchmarking of air quality model regulatory applications: the ‘target’ approach

The definition of appropriate performance criteria is one of the key issues for the benchmarking of air quality models in regulatory applications. As part of the FAIRMODE benchmarking activities (Thunis et al., 2010), suitable criteria for air quality modelling in the frame of the EU air quality directive (AQD) 2008 are proposed and tested. The suggested approach builds on the target indicator (Jolliff et al., 2009) as support to the relative directive error, the current official statistical parameter as defined in the AQD (EEA, 2011), for quantitatively estimating model performances in air quality modelling applications. This study describes the advantages of using the target compared to the actual limitations of RDE and addresses the main links between the target and some ‘traditional’ statistical indicators (MFB, R, FAC2, σ ). It also describes the application of this methodology to NO 2 , O 3 and PM 10 concentrations on three different model-observations datasets. Among these datasets two focus on the urban areas of Madrid and London and include modelled results provided by the air quality models CMAQ and ADMS-Urban for years 2007 and 2008 respectively. One other dataset (POMI) covering the Po valley and including multiple model results has also been tested for year 2005.