VI. SMOG WARNING AND REGULATORY SYSTEM
CHMI operates the Smog Warning and Regulation System (SWRS) on behalf of the Ministry of the Environment. Information obtained from this system serves both for warnings about extraordinarily high levels of air pollution (smog situations) and for regulation (reduction) of release of pollutants from selected sources significantly influencing ambient air quality in the given area. The monitored pollutants include the PM10 fraction of suspended particulate matter, sulphur dioxide (SO2), nitrogen dioxide (NO2) and ground-level (tropospheric) ozone (O3). SWRS was defined from 1 September 2012 by Act No. 201/2012 Coll., on protection of the air, and Decree No. 330/2012 Coll. The principal changes compared to the previous legislation were described in the CHMI Yearbook for 2012 (ČHMÚ 2013a) and in the article by Juras and Vlček (2013). Smog situations and regulation (or warning for ozone) are declared on the basis of exceeding of the threshold values. The establishment of SWRS rules (Table VI.1) led to smog situations and regulation for PM10 being declared and withdrawn with delays relative to the actual concentration trends. Consequently, CHMI prepared an amendment to Annex No. 6 of the Act on protection of the air, which was intended to eliminate this inadequacy (Vlček et al. 2015). The amendment came into effect on 1 January 2017 (Juras, Vlček 2017).
The current list of areas and representative stations for PM10, SO2 and NO2 (Fig. VI.1, VI.3, VI.4) is stipulated by the Journal of the Ministry of the Environment and, for O3 (Fig. VI.2), by a directive of the Director of CMHI for implementation of the Smog Warning And Regulation System (SWRS) in the territory of the Czech Republic. The list published in Journal of the Ministry of the Environment No. 10/2015 was valid for PM10, SO2 and NO2 in 2016 and the list in Journal of the Ministry of the Environment1 No. 7/2016 has been valid since October 2016. The list defined by Directive No. 2013/05 of the Director of CHMI was valid throughout the year for O3.
PM10, SO2 and NO2
In 2016, smog situations were declared only because of exceeding of the threshold values for PM10 suspended particulate matter. No smog situation was declared for NO2 and SO2.
Five smog situations were declared in 2016 because of high concentrations of suspended particulate matter PM10 with an overall duration of 387 h (approx. 16 days; Table VI.2, Fig. VI.5). All the smog situations were declared in January, in the O/K/F-M agglomeration without the Třinec area, in the Třinec area, in the central Moravia zone and in the Plzeň Region (Table VI.3). The overall small number of declared smog situations is related to the more favourable dispersion conditions in the colder part of the year, which were a result of the above-normal warm weather and the greater number of frontal systems crossing this country. The regulation threshold value for PM10 was exceeded in 2016 at some representative SWRS stations but, nonetheless, the legal conditions for imposing a regulation system were not met.
In addition to smog situations, all SWRS stations also recorded exceeding of the daily pollution limit value for PM10. The best conditions were in the Karlovy Vary Region (0.5% of days) and in the Vysočina Region (1.4% of days). On the other hand, the greatest number of days on which the daily pollution limit value was exceeded was recorded in the O/K/F-M agglomeration excluding the Třinec area (20.5% of days; Table VI.4).
Although the threshold values for NO2 and SO2 were exceeded at some SWRS stations during the year, further conditions for declaring a smog system and regulation were not met and thus these situations were not declared.
No smog situation was declared for tropospheric ozone in 2016.
Synoptic situation during selected smog situations
1–8 January 2016
The weather in the Czech Republic was influenced by the edge of a high pressure area over the Baltic Republics and the European part of Russia, initially in an unexceptional pressure field with calming winds. The inflow of cold air from the east to northeast, originating in the European part of Russia, gradually strengthened around this high-pressure area. In the first half of 1 January, a marked temperature inversion was present at a height of approx. 1 km, especially in Moravia and Silesia. In the second part of the day, the inversion weakened and the air became colder from the east, especially during 2 January. The air temperature was mostly below zero (Fig. VI.6). During 4 January, warmer air began to flow over the territory of the Czech Republic from the south-east in the higher layers of the atmosphere, leading to the formation of a marked temperature inversion at a height of about 1 km. On subsequent days, the warmer air gradually penetrated to lower altitudes, with a gradual decrease in the height of the inversion layer, which disappeared on 8 January and the dispersion conditions improved.
18 January 2016
On 17 and 18 January, a high-pressure area moved from the west into central Europe. During these days, in the cold air the sky cleared in some places; together with calming of the wind in the high-pressure area, this led to a temperature decrease at night and in the morning with the formation of groundlevel inversion with unfavourable dispersion conditions.