Previous atmospheric composition studies were based on extensive computer simulations carried out with good resolution using up-to-date modelling tools and detailed and reliable input data. The oncoming climate changes will exert influence on the ecosystems, on the all branches of the international economy, and on the quality of life. Regional climate models (RCMs) are important instruments used for downscaling climate simulations from Global circulation models (GCMs). The air quality (AQ)

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... t on human health and quality of life is an issue of great social significance. Evaluating this impact will give scientifically robust basis for elaborating efficient short term measures and long term strategies for mitigation of the harmful effects of air pollution. The AQ impact is evaluated in the terms of Air Quality Indices (AQI). Some extensive numerical simulations of the atmospheric composition fields in Bulgaria and Sofia have been recently performed. A quite extensive data base was created from simulations which were used for different studies of the atmospheric composition, including the AQ climate. Main aims of the numerical experiment presented in this paper are: (1) Adaptation and tuning of the RegCM model for the Balkan Peninsula and Bulgaria and thus development of a methodology able to predict possible changes of the regional climate for different global climate change scenarios and their impact on spatial/temporal distribution of precipitation, hence the global water budgets, to changes of the characteristics and spatial/temporal distribution of extreme, unfavorable and catastrophic events (drought, storms, hail, floods, fires, sea waves, soil erosion, etc.); (2) Development of a methodology and performing reliable, comprehensive and detailed studies of the impact of lower atmosphere parameters and characteristics on the quality of life (QL) and health risks (HR) for the population.