The number and size of urban conurbations, which comprise megacities and different urban agglomerations, collectively known as major population centres (MPC), has increased dramatically. By 2050, the population is predicted to rise to ~10 billion with about 75% being urban dwellers. MPCs require power, mostly generated from fossil fuel combustion for their transport systems, industry and domestic heating, cooling etc. MPCs are globally a growing and significant source of emissions of trace gases and aerosols into the troposphere. The air quality in the MPC and the transformation of the emitted pollutants is also often influenced by the transport of biomass burning and pollution plumes. Because of the variability of the naturally occurring emissions of trace constituents, the different characteristics of MPC, the mixing and interaction of the outflow from MPC with those from the surrounding areas, and the need to account for the local topography and meteorology, the assessment and prediction of the impact of pollution from MPC on tropospheric chemistry is challenging. The current knowledge of the effect of this anthropogenic pollution on the air quality and the regional tropospheric chemical composition, and its interaction with climate in a warming world is inadequate.
The trace constituent of interest from MPC emissions are short-lived climate pollutants, their precursors, and long lived greenhouse gases. To assess and better understand the local and regional impact of these pollutants, experimental and modelling investigations of the transformation of MPC emissions during their transport are required. This necessitates the consistent interpretation of observational data sets, having different spatial and temporal resolutions, generated from ground-based networks, airborne campaigns and satellite measurements. This further requires a hierarchy of model studies.
The purpose of this session is to present and discuss results from recent national and international projects studying the emissions from megacities and MPC and their transport and transformation. The session welcomes presentations about relevant observations, data interpretation and modelling studies. One focus is on the studies of MPC emissions from different continents, experiencing different meteorological conditions and the resultant local and regional impacts.