II.5 Evaluation of the Smog warning and regulatory system in the territory of the Czech Republic in 2012

Introduction
The Czech Hydrometeorological Institute (CHMI) authorized by the Ministry of the Environment operates the Smog warning and regulatory system (SVRS). Data provided by the system serve both for informing on the occurrence of the situation with increased concentrations of ambient air pollutants and for the regulation (limitation) of pollutants� release from the sources that markedly influence ambient air quality in the given territory. The monitored pollutants include PM₁₀ suspended particles, sulphur dioxide (SO₂), nitrogen dioxide (NO₂) and ground-level ozone (O₃).

Legislation
Starting from 1 September 2012 the operation of SVRS is newly regulated by Act No. 201/2012 Coll. on Clean Air Protection (further on the Act) and by the Bulletin of the Ministry of the Environment No. 9/2012. Formerly the legislative framework was set by the Act No. 86/2002 Coll., Decree No. 553/2002 Coll., as amended (mainly by the Decree No. 373/2009 Coll.), and by the Bulletin of the Ministry of the Environment No. 2/2010.

The new act replaced the term alert thresholds for the announcement of the warning signal and regulation with the terms informative threshold value and regulation threshold value. (As concerns ground-level ozone the warning threshold value instead of the regulation threshold value was set.) In order to stress the health risks connected with high concentrations of pollutants in the ambient air the smog situation is newly announced already on the exceedance of the informative threshold value.

Further change is connected with the territorial validity of SVRS. Smog situations and regulations are newly announced in the whole territory of the Czech Republic, which is divided for this purpose into areas tracing the territories of individual regions and agglomerations. The SVRS areas and the respective representative stations for SO₂, NO₂ and PM₁₀ were specified in the Bulletin of the Ministry of the Environment No. 9/2012. For the ground-level ozone they are set in the CHMI internal directive for the operation of the Smog warning and regulatory system in the territory of the Czech Republic (furtheron CHMI ID).

As compared with the old act, the relation between the source and the station is not regarded any more. Regulation is newly announced for all sources in the area, in which special operating conditions are established whenever the regulation threshold value is exceeded.

The new act brought stricter conditions mainly for the announcement of regulation caused by high PM₁₀ concentrations: the regulation for the given territory is announced when the 24-hour average concentration of PM₁₀ suspended particles exceeded at least at half of the stations representative for the given area the value 150 μg.m^-3 in three subsequent days, i.e. (according to the CHMI ID) the running 24-hour average concentration of PM₁₀ was exceeded in 49 subseqent hours. Simultaneously, at least one half of the stations representative for the given territory must record the increasing trend of 12-hour concentrations of PM₁₀ during the past 6 hours.

On the contrary, the conditions for the announcement of smog situations and warning due to high concentrations of ground-level ozone are now milder: for the announcement of the smog situation and warning it is sufficient if one station representative for the given period exceeds the average hourly ozone concentration 180 μg.m^-3 or 240 μg.m^-3, respectively.

The term smog situation will be used within the following text both for the smog situation according to the new legislation, and for the warning signal according to the old legislation. The term regulation should be understood both as the regulation according to the new legislation and the regulation signal according to the old legislation.

PM₁₀, SO₂ and NO₂
In 2012 smog situations were announced only due to high concentrations of suspended PM₁₀ particles. The smog situation was not announced neither for SO₂ nor for NO₂.

In total 16 smog situations were announced for PM₁₀ in 2012 lasting in total 80 days, and 5 regulations lasting 38 days (Table II.5.1). Smog situations wer most frequently announced in the territory of the agglomeration Ostrava/Karviná/Frýdek-Místek (O/K/F-M). The most extensive announcement as concerns the territory (including Bohemia) occurred in the first half of February, when smog situation was announced in 5 areas at the same time. The last smog situation of the year 2012 ended on 24 December (Fig. II.5.1). The overview of the detailed times of the announcement of smog situations and regulations is presented in Table II.5.2.

The exceedances of daily limit values of PM₁₀ occurred in the cold part of the year (January–March and October–December) at all SVRS stations. The best situtuation was in Karlovy Vary Region, South Bohemian Region and Vysočina Region. On the contrary, the highest number of days with daily limit value exceedance was recorded in the agglomeration O/K/F-M, Ústí nad Labem Region and Central Bohemian Region (Table II.5.3).

Meteorological conditions in the cold part of the year
As concerns temperature, the year 2012 in the territory of the Czech Republic was above the average and as concerns precipitation the levels were within the average. The average annual air temperture 8.3 �C was by 0.8 �C higher than the long-term normal of the period 1961–1990, the annual total precipitation 689 mm represents 102 % of the normal of the period 1961–1990.

At the beginning of the year 2012 warm weather prevailed in the territory of the Czech Republic, the average January temperature −0.2 �C was by 2.6 �C above the 1961–1990 normal. February was the coldest month of the year 2012 with average monthly temperature −5.2 �C, which is by 4.3 �C less than the 1961–1990 normal. The marked drop of air temperature caused by the break of arctic air from the east was recorded already in late January, low temperatures continued up to 13 February. The coldest weather was on 6 February when the minimum air temperature dropped in the whole territory of the Czech Republic below −14 �C, locally even below −30 �C. The break of the arctic air is well apparent in Fig. II.5.2; it resulted in extensive announcements of smog situations and regulations (Fig. II.5.1). March was warm in comparison with the normal; its average air temperature 5.1 �C was by 2.6 �C higher than the normal of the period 1961–1990.

October with the average temperature 7.4 �C ranks among the months with normal temperature, the deviation from the normal reached the value −0.6 �C. Strongly above the normal as concerns temperature was the month of November, the average monthly temperature 4.8 �C way by 2.1 �C higer the the normal from 1961–1990. December had also normal temperatures; its average monthly temperature −1.4 �C was only by 0.4 �C lower than the normal.

As concerns precipitation, January was strongly above the normal, the average total precipitation 81 mm represents 193 % of the normal from the period 1961–1990. The highest precipitation was recorded in the Liberec Region (140 mm, i.e. 203 % of the normal) and in the Karlovy Vary Region (121 mm, i.e. 216 % of the normal). The average monthly total precipitation in February 34 mm represents 89 % of the normal from the period 1961–1990. The March precipitation was below the normal, its total precipitation 15 mm represents 38 % of the 1961–1990 normal. The lowest precipitation was recorded in the South Moravian Region, the average March total precipitation reached the value 5 mm, i.e. 17 % of the 1961–1990 normal.
The values of average total precipitation in October, November and December fluctutated around the values of the normal.

Significant synoptic situations in the cold part of the year
27 January–15 February 2012
On 27.1. a massive anticyclone of 1055 hPa with the centre above Arkhangelsk spread up to the central Europe and blocked the move of frontal disturbances towards east. At the end of January 2012 the above anticyclone reached the value of 1065 hPa and its centre was located above the coast of the Barents Sea. During the first week of February the anticyclone of 1060 hPa with the centre above Scandinavia was formed, connected with the anticyclone above Siberia. In the rear of the cyclone 1030 hPa, advacing from the Baltic Sea to the south, the decaying occluded front passed over the territory of the Czech Republic on 9. 2. 2012. It brought about 6 cm of snow and the marked nocturnal radiation and amplification of temperature inversion. The episode ended on 15.2. by the passage of strong frontal system from northwest.

10–28 November 2012
On 10.11. the cyclone above the central Europe moved to the east. On 11 and 12 November the weather in the Czech Republic was influenced by undulated cold front lying in a trough of low pressure of the cyclone over the Norwegian Sea. During the following days the anticyclone progresssed from western Europe to central and eastern Europe and influenced the weather in the Czech Republic until 24.11. For most of the period warm air flowed to the territory of the Czech Republic, especially in higher layers of the atmosphere. The influence of this anticyclone was interrupted on 18.11. by a trough of low pressure of the cyclone above Iceland and the cold front lying in it, and partly also on 22 and 23 November, again by a trough of low pressure of the cyclone above Iceland. On 25.11. the undulated cold front moved from western to central Europe and it influenced the weather until the end of this period.

8–24 December 2012
On 8.12. the weather in the Czech Republic was influenced by a small area of high pressure. On 9.12. the frontal system from Germany moved to the territory of the Czech Republic. On 10 and 11 December the cyclone moved over the territory of the Czech Republic to Saxony and further to the north. On 12.12. the weather in the Czech Republic was influenced by the anticyclone above Bavaria. From 13 to 16 December the weather was influenced by the cyclone above the eastern Atlantic, on 15.12. the frontal system advanced over the territory of the Czech Republic to northeast. On 17 and 18 December the territory of the Czech Republic was influenced by the cyclone moving from the British Islands over France, and on 19 and 20 December by the edge of high pressure of the anticyclone above the European part of Russia. On 21 and 22 December the occluded front moved over Bavaria, Czech Republic and further to the northwest and on 23.12. the frontal system advanced over the territory of the Czech Republic to northeast. On 24.12. the impact of the cyclone over the eastern Atlantic prevailed.

Ground-level ozone
No warning signal was announced due to high ozone concentrations in 2012.

Temperature characteristic of the period
With regard to average daily temperatures measured at the station Prague-Libuš the period from 1. 4. to 30. 9. 2012 was normal with the deviation from the normal +1.4 �C and with slight temperature fluctuations. The daily temperature deviations from the normal ranged from +11.4 �C to −6.8 �C. Normal temperatures were recorded in April, July and September, May and June temperatures were above the normal and August temperatures were strongly above the normal. During the monitored period there occurred 19 days with the temperatures over 30 �C and the highest value 39.6 �C was measured on 20. 8. 2012. From 1. 4. to 30. 9. 2012 the total precipitation amounted to 407.4 mm, out of which 141.2 mm fell from 9. 7. to 30. 7. 2012. (Fig. II.5.4).

Occurrence of ground-level ozone
Increased ozone concentrations are usually expected in high air temperatures, clear or partly clear weather with low wind velocities. In 2012 the first case of the temperature above 30 �C was recorded on 29. 4. and the last one on 22. 8. 2012. According to the measurements at the station Prague-Libuš, between 1. 4. and 30. 9. 2012 there occured two periods with afternoon temperatures above 30 �C for 3 subsequent days as the minimum. The period of tropical temperatures was interrupted by cold air arrivals of various length (the most distinctive one lasted from 11.5. to 15.5, when the maximum daily temperature dropped from 30.7 �C to 10.0 �C). The longest period with tropical temperatures lasted from 19. 8. to 22. 8. (Table II.5.4).

The analysis of the occurrence of the highest average 1-hour concentrations of ground-level ozone in the territory of the Czech Republic from April to September 2012 shows that in April in Bohemia and in May in Moravia the concentration 160 μg.m⁻³ was reached in individual cases only, in June at the stations Beroun-Čertovy schody and Lom the values amounted to 172 μg.m⁻³, in July at 4 stations in Prague and at one station in Moravia they exceeded the alert threshold 180 μg.m⁻³ (Table II.5.5). In August 4 stations in Bohemia and 3 in Moravia recorded the highest values from160 to 164 μg.m⁻³, in September the values up to 150 μg.m−3 were measured in individual cases only.

Synoptic situation and weather from 22 to 28 July
On 22 July a ridge of high pressure formed from the anticyclone of 1028 hPa with the centre above the Azores which stretched eastwards up to the Moscow area. On the following day a separated anticyclone of 1030 hPa was formed above the central Europe and moved slowly eastwards; on 24. 7. its centre 1020 hPa was located above the Ukraine. On the following day the territory of the Czech Republic was influenced by a trough of low pressure from southwest and a separate cyclone of 1015 hPa was formed with the centre above Germany. On 26. 7. a mild pressure field was located above the central Europe and on the following day the ridge of high pressure reached to our territory from the north; in its rear culminated the inflow of warm air from the south. On 28. 7. at noon hours a strong cold front moved from the west over Bohemia followed by the exchange of air masses and drop of temperatures.

The weather in the Czech Republic: on 22. 7. the weather was mainly cloudy to overcast, with sporadic showers. The highest afternoon temperatures reached 17–21 �C. On 23. 7. the weather was partly cloudy, in Moravia even clear in the afternoon. The afternoon temperatures in the whole territory ranged between 22 and 26 �C, in Bohemia up to 29 �C in several places. On 24. 7. the weather in Bohemia was almost clear, in Moravia cloudy and the afternoon temperatures reached 24–29 �C. The temporary worsening of the weather started on 25. 7. – the sky was almost overcast, with occasional rain in most of the territory and the highest temperatures ranged from 20 to 25 �C. On the following day the weather in Bohemia was partly cloudy to cloudy, in Moravia cloudy to almost overcast, the showers occurred only sporadically. The maximum temperatures in Bohemia were from 26 to 32 �C, in Moravia from 22 to 26 �C. On 27. 7.the weather in Bohemia was almost clear, in Moravia cloudy, the temperatures in Bohemia amounted to 28–33 �C, in Moravia up to 30 �C. On the following day the morning weather was partly cloudy, at noon hours cloudy to overcast on the cold front with showers and storms. The temperatures before the front reached 28–33 �C, after the front passage they decreased by about 10 �C.

In the period 22–24 July 2012 ozone was formed during the days and in night hours it cummulated in the central and upper parts of the mixing layer; this process was interrupted for a short time on 25. 7. On the following two days the concentrations increased again and the maximum values were reached on 27. 7. in the afternoon hours. With regard to wind velocities around 1 m.s^-1 and variable wind direction the highest concentrations were measured in Prague, i.e. in the area of high occurrence of ozone precursors. On the following day there occurred the exchange of air masses and the marked decrease of ground-level ozone concentrations was recorded (Fig. II.5.5). On 19.–22.8. 2012 the highest air temperatures were measured, however the analysis of the synoptic situations shows that during the mentioned period weak cold fronts decayed over the territory of the Czech Republic and thus no exchange of air masses occurred.

Tab. II.5.1 Number and duration of smog situations and regulations due to high PM₁₀ concentrations

Tab. II.5.2 Detailed overview of the announced smog situations and regulations for PM₁₀ in 2012

Tab. II.5.3 Number of days and their share [%] in the periods 1 January–31 March and 1 October–31 December during which at least one station representative for the given SVRS area exceeded the set limit value or the threshold value

Tab. II.5.4 The periods with the maximum daily temperatures exceeding 30 �C on at least three subsequent days and maximum 1-hour concentrations of O₃ during these periods in the Czech Republic

Tab. II.5.5 Occurrence of O₃ concentrations exceeding the alert threshold 180 μg.m^-3 and the length of continuous duration

Fig. II.5.1 PM₁₀ - total overview of the announced smog situations and regulations, 2012

Fig. II.5.2 The average daily air temperature, its long-term normal and daily total precipitation at the station Prague-Libuš for the period 1.–31.3.2012

Fig. II.5.3 The average daily air temperature, its long-term normal and daily total precipitation at the station Prague-Libuš for the period 1.10.–31.12.2012

Fig. II.5.4 The course of temperatures and precipitation at the station Prague-Libuš with the indication of the days with ozone concentrations above 180 μg.m⁻³

Fig. II.5.5 Spatial distribution of maximum daily 1-hour concentrations of ground-level ozone in the territory of the Czech Republic, 25.7.–29.7.2012