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Megacities: Emissions, urban, regional and Global Atmospheric POLlution and climate effects, and Integrated tools for assessment and mitigation

Periodic Report Summary - MEGAPOLI (Megacities: emissions, urban, regional and global atmospheric pollution and climate effects, and Integrated tools for assessment and mitigation)

MEGAPOLI will contribute to the strategic goal of promoting sustainable management of the environment and its resources by advancing our knowledge on the interactions between air quality, climate and human activities related to large urban centres and hotspots. The main MEGAPOLI objectives are: (i) to assess impacts of megacities and large air-pollution 'hot-spots' on local, regional, and global air quality and climate; (ii) to quantify feedbacks between megacity emissions, air quality, and local, regional and global climate; (iii) to develop and implement improved, integrated tools to assess the impacts of air pollution from megacities on regional and global air quality and climate and to evaluate the effectiveness of mitigation options.%
LThe main scientific results achieved during the reporting period include the following:
1. Two intensive measurement campaigns were performed around Paris during summer and winter month periods. The campaigns aimed at better quantifying primary and secondary organic aerosol (SOA) sources for a European megacity, and included 3 primary and 7 secondary fixed ground measurement sites, an aircraft and 5 mobile vans. More than 25 research laboratories participated. We found that the pollution plume was still well defined at more than 100 km downwind from the agglomeration, which gives a clear framework for later studying SOA build-up in the plume. Significant new particle formation events were frequently observed during the campaigns.
2. Prototype inventories for anthropogenic (base year 2005, 6 km resolution) and natural (e.g. fire, sea salt) emissions was compiled. For the first level megacities (Paris, London, Rhine-Ruhr area, Po Valley) high-resolution emission data have been collected, for integration with the final European scale emission map. An anthropogenic heat flux (AHF) model (0.25 x 0.25 arc-minute resolution) was developed and used to compute the AHF inventories for Europe and London.
3. A morphology database for Paris has been developed, along with a hierarchy of urban canopy and energy budget parameterisations for different scale models, which are being used to evaluate the surface flux balance modelling and urban features needed for climate and air quality models.
4. New physical and chemical parameterisations and sooming approaches have been implemented and are being tested for several megacities, providing information about the relative importance of the various parameterisations when examining megacity air quality and especially its relation to meteorology. Coupled ACT-NWP models with two-way feedbacks were used to classify meteorological patterns favouring development of urban air pollution episodes in European megacities. Urban aerosols were found to significantly affect several meteorological variables (temperature, inversion layers, radiation budget, cloud processes, precipitation, fog, etc.) in and far from the megacities due to the direct and indirect effects.
5. Substantial progress was made in developing and evaluating the satellite-based methods for the measurement of tropospheric gases and aerosols, especially NO2, in and around megacities.
6. The radiative forcing from megacity emissions on the global scale was examined. Generally, megacities contribute about 2% to 5% of the total global annual anthropogenic emission fluxes for various compounds. Megacity pollutants were found to contribute a radiative forcing of +6.3±0.4 mW/m2 from an increase in the osone burden, while the impact on CH4 contributes a forcing of -1.0±0.5 mW/m2. The aerosol forcing from megacity pollutants amounts to -8.0±1.6 mW/m2 under present-day conditions.
7. Progress has been made on producing a European framework for online and offline coupling of meteorological and atmospheric chemical transport models.

The achieved results have been reported in 15 scientific MEGAPOLI reports and in a number of publications (see project website at http://megapoli.info online).

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