National Committee on Ecology and Climate Change of the Republic of Uzbekistan

The first is an increase in heating-related emissions. As temperatures begin to fall in autumn and winter, the demand for heating buildings rises. As a result, the amount of pollutants released into the atmosphere through heating activities also increases. Residential heating is one source of these emissions. In Uzbekistan, heating greenhouses is another significant contributing factor.

In spring and summer, when temperatures are higher, the demand for heating decreases or disappears altogether. Consequently, heating-related emissions are significantly lower during these seasons than in autumn and winter. During the colder months, these emissions become an additional source of air pollution.

The second major factor is the meteorological conditions typical of winter, particularly changes in the movement and mixing of air masses. Atmospheric mixing is generally less effective in winter than in summer. During summer, air layers mix more readily, allowing pollutants to disperse throughout the atmosphere. In winter, however, mixing in the lower atmosphere becomes weaker, limiting the dispersion of pollutants.

During this period, the height of the atmospheric boundary layer decreases. This is the lowest layer of the atmosphere, where the Earth's surface has the greatest influence on air movement and mixing. As a result, pollutants are less likely to rise and disperse over wider areas. Instead, they tend to accumulate close to the ground, in the layer of air that people breathe.

Therefore, in autumn and winter, not only do emissions of air pollutants increase, but conditions for their dispersion also become less favourable. These two factors — increased heating-related emissions and unfavourable meteorological conditions — are the main reasons for the deterioration of air quality during the colder months.