SPATIO-TEMPORAL ANALYSIS OF FOG RECURRENCE IN THE PERM REGION AND ITS IMPACT ON ATMOSPHERIC POLLUTION

The article presents a spatio-temporal analysis of fog recurrence according to data from 11 weather stations in the Perm region. The effect of fog on air pollution in the cities of the region is also considered. The study period is 1999-2016. Fogs in Perm Krai are observed throughout the year. Their distribution by month and territory is uneven. The maximum number of days with fogs is observed in warm seasons. Fogs are most often observed in Perm Krai in Cherdyn, Vaya and Oktyabrsky weather stations, mainly in August-October. The synoptic situations in which fogs are most often observed in the region include low-gradient field, warm cyclone sector and anticyclone centre. These account for more than 70 % of all synoptic situations in which fogs were observed. The level of air pollution at these synoptic situations was high and low. High level of air pollution on days with fogs was created in Perm at the south-western periphery of the anticyclone and in the centre of the anticyclone, in Gubakha - at the northern, eastern and south-western periphery of the anticyclone. In the towns of Berezniki and Solikamsk, no dangerous air pollution levels were observed on days with fogs. Analysis conducted to identify cases of exceeding Maximum Permissible Concentrations (MPC) of pollutants in fogs showed that cases of exceeding MPC were quite frequent. In Perm, Solikamsk and Gubakha cities MPC exceedances for formaldehyde account for 40 - 77 % of all impurities. In Berezniki, nitrogen dioxide and hydrochloric acid account for 65 % of all MPC exceedances.