The effect of meteorology on air pollution in Moscow during the summer episodes of 2010

Relations between short-term variations in the concentrations of aerosol (PM₁₀) and carbon monoxide (CO) and meteorological characteristics are considered for the episodes of severe atmospheric pollution in the region of Moscow in the summer of 2010. The assumption is made and substantiated that the observed (in late June) severe aerosol pollution of the atmosphere over Moscow was caused by air masses arrived from soil-drought regions of southern Russia. In August, during the episodes of advection of forest-fire products, the maximum surface concentrations of pollutants were observed in Moscow mainly at 11:00–12:00 under a convective burst into the atmospheric boundary layer and at night in the presence of local wind-velocity maxima or low-level jet streams within the inversion layer. On the basis of results from an analysis of these air-pollution episodes before and after fires, it is concluded that the shearing instability of wind velocity favors the surface-air purification under ordinary conditions and an increase in the surface concentrations of pollutants during their advection (long-range transport, natural-fire plumes, etc.). It is shown that the pollution of the air basin over the megapolis with biomass-combustion products in 2010 led to an increase in the thermal stability of the atmospheric surface layer and in the duration of radiation inversions, as well as to an attenuation of the processes of purification in the urban heat island.