Megacities in Focus

The project will address, at different levels, practically all major megacities around the globe. Three levels of detail will be used in MEGAPOLI (Figure 4). The lowest level of detail (3rd level in Figure 4) will include all megacities and the corresponding investigation will have a global perspective looking at their effects on global air quality and climate. The corresponding tools will include global Chemical Transport Models (CTMs), Global Climate Models (GCMs) and satellite studies. For cities in the 2nd level a regional perspective will be added to the global one. These cities (Moscow, Istanbul, Mexico City, Beijing, Shanghai, Santiago, Delhi, Mumbai, Bangkok, New York, Cairo, St.Petersburg and Tokyo) have been selected because they are a representative subset of the full megacity set, they have been the locations of air quality studies and there are available observation datasets. The MEGAPOLI team includes local collaborators from these 2nd level megacities (see Section 2.3) who will help in achieving the project objectives and will benefit from our results. MEGAPOLI will combine the available datasets in these megacities with regional models (including selected urban scale model applications) and also apply there the Integrated Modelling Tools that will be developed and evaluated in the project. The tools of the 3rd level will also be applied to the 2nd level megacities. Finally, for the 1st level megacities an urban and street scale perspective will be added to the regional and global ones. These megacities are the four major European Union population areas (Paris, London, Rhine-Ruhr, and Po Valley). New air quality observations will be collected for Paris closing some of the important gaps in the existing measurements. The resulting dataset in Paris together with existing datasets in the other areas will be used for the evaluation and improvement of the modelling tools in MEGAPOLI. Finally our mitigation and policy analysis activities will focus on these 1st level megacities.

Paris and London are the only two cities within the European Union that strictly correspond to the definition of a megacity (i.e. population larger than 5 million people). The Rhine-Ruhr and Po Valley areas have megacity features even if they can be better described as urban conglomerations than as a single metropolitan area (Figure 5). The estimated loss of life expectancy due to air pollution is quite high in these areas (Figure 6) and therefore, attaining the air pollutant concentration limits, imposed by the EC air quality framework, and daughter directives is presently critical for different air pollutants, e.g. PM and NO2.

The pyramid of megacities in focus in MEGAPOLI

Figure 4: The pyramid of megacities in focus in MEGAPOLI.

Paris, with the belt of surrounding suburbs, is the largest metropolitan area in Europe, with a population around 11 million people. The very dense urbanised area is concentrated on a limited surface, a quasi circle with about 20 km diameter, surrounded by rural areas. The city and surroundings are located in flat terrain; regional atmospheric circulation is thus mainly driven by synoptic scale weather patterns. Due to strong and concentrated emissions, several air quality standards are exceeded within the urban agglomeration, especially annual average NO2 and PM10 concentrations. Ozone concentrations reach often very high values in the Paris plume. However, detailed aerosol measurements (chemistry and size distribution) and quantitative knowledge on particulate matter sources in the area is lacking and little information exists about the Paris plume. Moreover, air pollution episodes have been recently very probably accentuated by climate change, as for example during the summer 2003 heat wave. These different reasons led us to the choice to carry out the MEGAPOLI field measurements in and around Paris (WP3). Indeed, the relative isolation of Paris from other major urban areas makes it a suitable location for the investigation of the regional effects of megacities and the physical and chemical evolution of the corresponding pollutants, both in the urban area and in the plume (WP4 and WP5).

The Rhine-Ruhr and Po Valley basins suffer air quality conditions worse than those experienced by Paris and London. This is mainly due to high urban and industrial emissions and to the adverse meteorological conditions that often affect the two regions. The Po River Basin includes six administrative regions, and has a total population of about 16 million people. The Basin accounts for 40% of Italy’s GDP. It is home to 37% of the country’s industry, about 55% of livestock, and 35% of the country’s agricultural production. The Po valley is therefore exposed to substantial emission loads. The atmospheric circulation of the Po valley is characterised by the strong modification of synoptic flow due to the high mountains that surround the valley on three sides. The local atmospheric circulation features, dominated by calms and weak winds, favour the development of critical pollution episodes. Milan city and its surrounding urban area is located in the flat central part of the Po river basin. The core of Milan urban area, roughly coincident with its province, accounts for 3.7 millions inhabitants, while the commuting area includes around 7 million people (OECD, 2006). During the last decades, the urbanisation of the surrounding region has been enhanced by the re-settlement of part of the population from the city core to the surrounding region. The Rhine-Ruhr area is situated in the state of North Rhine-Westphalia, in Germany’s industrial heartland. It is home to cities like Bochum, Bottrop, Dortmund, Duisburg, Essen, Gelsenkirchen, Köln, Leverkusen, Solingen and Wuppertal, covers an area of about 10.000 km2 and has a total population of more than 10 million people. With frequent west and south-west winds, the Rhine-Ruhr region is also downwind of other European megacities (London and Paris) and impacted by emissions from the Netherlands. Therefore, this region is not only exposed to “home made” new emissions but also to aged air from neighbouring regions. Due to the mostly hilly terrain of the region, air pollution and local climate are very heterogeneous and quite locally influenced.

Population density in EU for 2003 (Source Eurostat) Loss in life expectancy (months) attributable to exposure to anthropogenic PM2.5 for year 2000 emissions (Source: EC, IIASA)
Figure 5: Population density in EU for 2003 (Source Eurostat) Figure 6: Loss in life expectancy (months) attributable to exposure to anthropogenic PM2.5 for year 2000 emissions (Source: EC, IIASA)

The four megacity areas identified above have different urban features and cover a wide range of topography, climate and atmospheric circulation conditions, providing a variety of different test cases for the evaluation and application of the MEGAPOLI modelling tools and the assessment of mitigation scenarios.

Many fast-growing cities are located within and nearby Europe (e.g. Moscow, Cairo and Istanbul) and can directly affect European air quality and climate for example in the climate-change sensitive Mediterranean Basin. Moreover, the largest megacities with populations exceeding 20 million and showing continuous growing tendency, are located in developing countries in other continents. In those megacities air pollution abatement policies are still in their infancy and their emissions are expected to have a large effect on regional and global air quality and also climate. For these reasons the analysis of megacities effects at regional scale (WP1, WP4 and WP5) will include the 2nd level megacities listed in Figure 4. Mexico City will be investigated in detail because of the availability of state-of-the-art datasets (the MILAGRO campaign of 2006 and the MCMA-2003 campaign) and the existing links to the MILAGRO team and the Mexico City studies. Specific activities will be devoted to trans-continental transport of megacity pollutants (WP5: influence of Boston/New York/Washington area emissions on Europe). The effects of all the megacities distributed worldwide will be considered to quantify their overall effects on global air quality and climate (WP5 and WP6).


FP7 EC MEGAPOLI, 2008-2011