Meteorological Potential of the Diffusing Capacity of the Atmosphere

Presented are the results from investigating the atmospheric self-purification capacity over the cities of Irkutsk, Beijing and Ulaanbaatar for the summer and winter seasons of 2017-2018. The meteorological potential of the atmosphere (MPA) was used as the criterion for assessing the atmospheric self-purification. It is shown that in the summer season of 2017 the favorable meteorological conditions for the dispersion of air pollutants were dominant over the territory of Irkutsk and Ulaanbaatar. In the summer, MPA was 0.99 and 0.78 in Irkutsk and in Ulaanbaatar, respectively. MPA varied from 2.14 to 4.66 in Beijing in the summer. For the winter months in the three cities, MPA > 1, which indicates an accumulation of pollutants in the atmosphere for that season. In Ulaanbaatar there were unfavorable conditions for self-purification: the maximum MPA index (9.5) was observed in December. The largest contribution to impairment of the atmospheric diffusing capacity over Ulaanbaatar in the wintertime was made by wind velocities of 0-1 m/s. It was found that the maximum accumulation of pollutants in the atmosphere over Beijing occurs in the winter. MPA varied from 15.0 in February to 19.0 in December, averaging 16.68. Fogs made the largest contribution to the unfavorable meteorological conditions of Beijing in December-February. The characteristic properties of the atmospheric circulation, wind regime, fog and atmospheric precipitation were responsible for MPA of Irkutsk, Ulaanbaatar and Beijing for the period under consideration.