CityZen Objectives

CityZen aims at determining the air pollution distribution and change in and around hotspots over the last decade from extensive satellite and in-situ observations and employs a series of different scale models to analyze the impacts of air pollution hot spots on regional and global air quality, including potential future changes for various climate scenarios. The focus is on ozone and particulate matter (chemical and physical characterization), and their precursors. The Eastern Mediterranean (Istanbul, Athens, Cairo), the Po Valley, the BeNeLux region, the Pearl River Delta in China (including Guangzhou and Hong Kong) and the hot and polluted European summers 2003 and 2007 are chosen for case studies. The consortium includes experts on observations, emission data and modeling. A set of chemical transport models connecting the most important spatial and temporal scales is further developed and used to quantify how the observed air pollution arises. Models and emission inventories are evaluated, errors identified and improved on the urban, regional and global spatial scales. Climate change may cause changes in air pollution in and around hotspots, and hotspot pollution can change precipitation and temperature/albedo. These feedbacks are studied in scale-bridging model systems based on global climate model scenarios, and in a coupled high resolution chemistry-climate model. The model systems evaluated in the project are applied to analyse mitigation options in and around hotpots, also taking into account climate change. Best available technologies and sectoral changes are studied. Several partners have key roles in the technical underpinning of policy. They will ensure that the improved emission inventories, scale-bridging model systems and the systematic observational evidence has a significant, broad and lasting impact.

• Quantify and understand current air pollution distribution and development in and around selected megacities/hot spot regions, including the interaction across the different spatial scales
• Estimate the future impact from emission changes with a focus on the effect of rapid growth in the population of megacities/hot spots and the increasing background of pollutants (concentrate on ozone, particulate matter PM, and their precursors)
• Estimate how megacities/hot spots influence climate change
• Estimate how megacities are responding to climate forcing which can influence transport patterns, chemical oxidation and biogenic emissions (especially biogenic volatile organic compounds BVOC)
• Study mitigation options, e.g. by introducing biofuel, to keep the air pollution load in and around megacities/hot spots within sustainable limits in terms of human health effects and climate impact.
• Develop tools to estimate interactions between different spatial scales (megacities to global)
• Bring the scientific results and methods developed and applied during the course of the project to semi-operational use with those consortium partners that on a more permanent basis provide technical underpinning of policy work, that is, ensure an excellent return on the investment in the project both during and after the project has ended.

• Megacities and hot spots have changed the regional and global distribution of ozone, particulate matter, and their precursors including carbon monoxide CO and other pollutants significantly compared to what would be the case with more evenly distributed emissions.
• Megacities affect the radiative budget and aerosol microphysics such that precipitation and the number of sunlit hours and thus temperature and photochemistry change significantly both locally and over larger regions. This may become more significant in the future as megacities and their emissions grow.
• Climate change will change weather patterns (winds, temperature, stability, precipitation) and surface properties, which affect air quality in megacities and regional hot spots. If more frequent high pressure situations occur, episodes with reduced air quality will become more frequent.
• Climate change will induce episodic and permanent changes in the natural and anthropogenic cycles of atmospheric trace chemicals.
• Changes in frequency and intensity of forest fires and other biomass burning will at times contribute significantly to air pollution in megacities and hot spots.
• Measures can be defined that reduce the adverse effects of megacity/hot spot emissions. The adverse effects relate both to air quality (human health) and climate change/weather modification.
• The effect on air quality in some megacities following the replacement of gasoline in parts by biofuel is to reduce the formation of secondary pollutants: aerosols and ozone.