A) One of the fundamental challenges of a liveable environment today is to ensure adequate urban air quality. Atmospheric pollutants associated with transport, energy and industrial production, as well as solid aerosol particles, pose a serious health risk. Under certain meteorological conditions, these substances may be enriched in the near-surface air layer and may develop smog. In recent decades, urban air quality has improved slightly, but compliance with tighter regulation is very difficult and keeping aerosol concentration below the limit value is almost impossible. Most European countries are therefore subject to infringement proceedings. The identification of air pollution and meteorological factors is an important element in improving air quality and mitigating adverse effects. The interaction between air pollution and meteorological situations may result in severe hazard or economic damage. These include a drastic reduction in visibility, the formation of dense fog, which could, among other things, lead to the impossibility of air transport and major accidents in road transport. One of the conditions for ensuring a sustainable environment is that such situations, which cannot be avoided, can be predicted as accurately as possible. In order to develop reliable atmospheric forecasting models, it is necessary to know the chemical and physical processes that determine the role of airborne and liquid water in the formation and aggravation of air pollution situations. If the planned project is implemented, we will be able to forecast dangerous or unfavourable air conditions on a regional scale with a much higher degree of reliability, taking into account the interaction between air pollution and meteorological situations based on measurements. B) Introduction, air quality in Europe has improved in recent decades, mainly due to reductions in SO2 emissions. However, for other air pollutants (e.g. NOx, dust), this reduction is unclear. These substances may continue to occur at concentrations posing a risk to health. The whole of Europe faces similar air pollution problems, since in addition to local sources, long-distance transport across borders also plays a role in the development of air pollution. The relationship between air quality and weather is a long-known fact. Already at the beginning of the 20th century there was serious air pollution in London, in which the smog, which remained stable for several days, with low air movement and preventing the vertical mixing of the atmosphere, played a significant role. At the beginning of the last century, the winter smog periods were characterised by a high concentration of SO2, various acids and soot in addition to aerosol particles. This has changed today, with a large increase in mass concentrations of PM10 (particles of less than 10µm) being the main problem in winter. Background The limit value for the daily average concentration of PM10 for the protection of human health under the current EU directive is 50 µg/m³ and the limit value must not exceed 35 days per year. In the last 10 years in Budapest, there have been only 2 years when we did not reach this threshold. The mass concentration of aerosol particles is determined by a standardised procedure, the error or environmental sensitivity of which is unclear at international level. Especially in the case of fog, when PM10 concentrations may be increased by adsorption of water present in the atmosphere. Local PM10 sources have a seasonal run, and the formation of smog is mainly due to unfavourable weather and flow conditions, mainly in winter, by long-range transport. These impacts can only be assessed together and the negative air quality situation can only be predicted by a complex model system. A high resolution grid point emission database, meteorological data and appropriate initial and limit conditions are required for the model system to adequately predict the concentration of each pollutant. In Hungary, such air pollution episodes develop mainly in cold-air cushion situations, which is a characteristic of the Carpathian Basin. As the atmospheric conditions that cause the formation of fog also favour the formation of smogs typical of large cities causing health problems (Hu et al, 2105), a number of research projects have been launched to study the processes leading to the formation of fog. Although fog is a common phenomenon that affects our daily lives, there are still a number of problems that need to be solved for its reliable prediction. These include the analysis of the interaction between aerosol particles and the water droplets that make up the mist, chemical reactions in water droplets, and the study of the interaction between the surface and the atmosphere on a scale of a few hundred metres (Gultepe, 2007). Novelty of the project The air pollution