II.5 Evaluation of the smog regulation systems operation on the territory of the Czech Republic in 2009

The temperatures of the first two and the last two winter months of the year 2009 were slightly variable. In January 2009 the average monthly temperature -4.0 �C was slightly subnormal with the deviation from the normal -1.2 �C, November 2009 with the average monthly temperature 5.5 �C was markedly above the normal, with the deviation +2.8 �C. The months of February and December 2009 with average monthly temperatures 1.0 �C ranged around the long-term normal. As concerns the monthly precipitation amounts, the highest values were recorded in February – 61 mm and in December – 58 mm, which represents 161�% and 122 % of the long-term normal respectively. The average precipitation in January and November 2009 amounted to 25 mm and 43 mm, which represents 60 % and 88 % of the long-term normal respectively. According to the results of the Prague-Libuš station the period from 1.1 to 17.1. 2009 was markedly below the normal, with maximum deviation from the normal -10.9 �C on 9.1.2009; the beginning and the end of the period 18.1.–10.2.2009 were slightly above the normal, with the deviations from the normal up to +3.8 �C. The period from 11.2 to 21.2.2009 was slightly below normal, with the highest deviation from the normal -4.0 �C on 19.2.2009. In the remaining days of February both the temperatures and the deviations increased, the maximum deviation from the normal +4.9 �C was recorded on 28.2.2009. The average daily temperatures from 1.11. to 31.12.2009 can be divided into two periods, one with the markedly plus deviation and the other with the minus deviation from the long-term normal. The period from 12.11. to 1.12.2009 had markedly above-the-normal temperatures, the average daily temperature on 17.11. was 14.1 �C and the deviation from the normal +10,8 �C. Another period with markedly subnormal temperatures was between 12.12. and 22.12.2009; on 20.12. the average daily temperatures was -12.4 �C and the deviation from the normal was -13.1 �C. As regards the long-term normal of precipitation, the maximum amounts were recorded in December – 53 mm, which is 215.4 %, and in February 2009 with the sum of 24.8 mm, i.e. 122.2 % of the long term normal. There follow further months, and namely January with 17 mm, i.e. 47.0 % and November with 22.3 mm, which represents 71.7�% of the long-term normal (Figs. II.5.1 and II.5.2).

Anticyclonic situations in January–February and November–December 2009 occurred in 16.7�% of cases and their relative frequency for the above months was unsteady and ranged between 0 and 29.0 %. The highest relative frequency of the occurrence of anticyclonic situations (29.0 %) was in January 2009, in February 2009 there was no such situation. In November 2009 the anticyclonic situations were recorded in 23.3 % and in December 2009 in 12.9 % of cases. Very high occurrence of cyclonic situations in February and December 2009 resulted in above-the-normal precipitation amounts in the mentioned months.

From 1.1. to 28.2.2009 and from 1.11. to 31.12. 2009 concentrations of SO₂ exceeding 250 μg.m^-3 were recorded in the territory of the Czech Republic in 11 cases, 9 of them in January 2009. There were no episodes lasting for continuous 3 hours and more, only one-hour exceedances were recorded. The most frequent exceedance of this limit value was recorded in the Krušné hory Mts., due to the impacts of smoke plumes from power stations with the terrain in the mountain ridges. The highest SO₂ concentration was measured on 13.1.2009 at the station Rudolice v Horách (675 μg.m^-3).

From 1.1. to 28.2.2009 and from 1.11. to 31.12. 2009 there were recorded concentrations of NO₂ above 200 μg.m^-3 for 3 subsequent hours and more only at the station Prague 2-Legerova, and namely on 4 days: 15.1.2009 from 13:00–17:00 with the maximum value 251 μg.m^-3, on 10.2.2009 from 06:00–08:00 with the maximum value 220 μg.m^-3, on 9.10.2009 from 13:00–17:00 with the maximum value 258 μg.m^-3 and on 21.12.2009 from 14:00–17:00 with the maximum value 248 μg.m^-3 (Figs. II.5.3 and II.5.4). The 1-hour limit value was exceeded also at the station Uherské Hradiště. In all cases the NO₂ concentrations decreased very quickly, the expected significant increase did not occur, and, consequently, the conditions for the announcement of the SRS signals were not fulfilled.

The major problem in ambient air duality throughout the Czech Republic is caused by the occurrence of high concentrations of PM10 fraction of particles. In the period of 9.1.–16.1.2009 the air quality in the whole territory of the Czech Republic deteriorated, the worst situation was on 14 and 15 January, when the limit value was exceeded at 54 measuring stations, which is 61 % of the total number. The greatest number of stations with exceedances was recorded in the Ostrava area, Prague, Central Bohemian Region and Ústí nad Labem Region. The analysis of the occurrence of the anticyclonic character of the weather and the mightiness of vertical air temperature inversion during the noon show that the worst dispersion conditions occurred from 7.1. to 17.1.2009. The graphs in Figs. II.5.5 and II.5.6 show clearly that the situation in the Moravian-Silesian Region is critical because the concentrations are very high and they are recorded more frequently than in other parts of the Czech Republic.

The development of synoptic situation from 8.1. to 15.1.2009
Between 8. 1. and 10. 1. 2009 the weather in the Czech Republic was influenced by the anticyclone 1035–1038 hPa, first with the centre above Hungary, later above the Carpathians. From 11.1. to 13.1.2009 the weather above the territory of the Czech Republic was influenced by the anticyclone 1040–1038 hPa, which moved from Hungary to the Black Sea. On 14.1. the influence of this anticyclone markedly declined and there was a flat low over the Czech Republic territory. On 15.1. there occurred the anticyclone 1027 hPa above Scandinavia and cold air began to move from the north on its front side. From 8.1. to 10.1.2009 at the level of 850 hPa (about 1500 m n.m.) there prevailed the advection of cold air, from 11.1. to 13.1. there prevailed the advection of warm air and thus there occurred the increase of the temperature gradient and of the intensity of the temperature inversion. On 12.1. at 12:00 UTC, according to the radiosounding measurement, in the layer from 745 m to 1181 m n.m. the temperature increased by 18.0 �C. The marked temperature inversion lasted from 9.1. till 14.1.2009. On 15.1.2009 at noon there was only weak temperature inversion and the dispersion conditions were much better.

Occurrence of tropospheric ozone from 1.4. to 30.9. 2009
As regards the maximum daily temperatures at the station Prague-Libuš, the period from 1.4. to 30.9.2009 was slightly above the normal with the deviation +2.4 �C, but the temperatures were rather fluctuating. Daily temperature deviations from the normal ranged in the interval from +12.0 �C to -8.8 �C. The highest average monthly temperature deviation in the monitored period was +6.4 �C in April, the lowest one –0.5 �C in June, the deviations in the remaining months ranged from +1.0 �C to +3.6 �C. In the monitored period there were 11 days with the temperatures above 30 �C; the highest value 34.9 �C was measured on 23.7.2009 (Fig. II.5.7).

The increased ozone concentrations can be expected with the occurrence of high air temperatures, when the weather is clear or somewhat clear with low wind velocities. Between 1.4. and 30.9.2008, according to the records of the station Prague-Libuš, there occurred 3 periods during which the afternoon temperatures exceeded 30 �C for two subsequent days.
 

The analysis of the occurrence of the highest average hourly concentrations of tropospheric ozone in the territory of the Czech Republic from April to September 2009 shows that the highest values (201–207 μg.m^-3) were measured in August in the Ústí nad Labem Region, followed by July with the concentrations around 170 μg.m^-3 in the Zlín Region and the Moravian-Silesian Region, May with 169 μg.m^-3 in the Ústí nad Labem Region, April with 153 μg.m^-3 in the Olomouc Region. In the remaining months, in June in the Hradec Králové Region and in September in the Plzeň Region, the values reached 148 μg.m^-3. It can be concluded that in 2009 the highest and most frequent concentrations of troposheric ozone were recorded in the Ústí nad Labem Region.

One-day episode of concentrations exceeding the alert threshold value 180 μg.m^-3 was recorded on 2 August 2009, when this value was exceeded for subsequent 3 hours at the stations Lom and Teplice, with the maximum concentration 207 μg.m^-3. The mentioned day was characterized first by the influx of warm air from the south-east, but mainly by the weakening flow in the whole mixing layer (in the morning and late morning hours was very weak, the average velocity at the level 0–500 m above the terrain was 6.7 km.h^-1. Under such conditions there occurred a great accumulation of ozone precursors in the given locality and therefore the O₃ concentrations at the stations of northern Bohemia increased in the average by 27 μg.m^-3 with regard to the previous day, and namely at the stations Teplice (by 65 μg.m^-3) and Lom (by 75 μg.m^-3) which represents the extreme increase. The station Prague-Libuš recorded the increase by 53 μg.m^-3 (Fig. II.5.8).

Synoptic situation and the weather from1 to 3 August 2009
On 1 August 2009 the weather in the Czech Republic was influenced by the anticyclone 1023 hPa with the centre above Poland, which gradually weakened and moved eastwards. On 3 August its centre 1018 hPa was above the eastern coast of the Black Sea. In the same time the filling cyclone 995 hPa with the centre above the northern Ireland moved northwards and at the end of the monitored period its centre of 1005 hPa was over Iceland. On 2 August the warm air inflow to the central Europe culminated at its front side, which was stopped on the same day in late afternoon hours by the passage of the cold front, followed by the ridge of high pressure on 3 August.

On 1.8.2009 the weather in the whole Czech Republic was clear, with the exception of north-eastern Moravia with local cloudy weather. Maximum afternoon temperatures reached 26.9��C. In the morning of the following day the weather in Bohemia was almost clear, in the afternoon gradually cloudy from the west, temporarily overcast with showers. In Moravia, the weather was almost clear for the whole day, in the evening and during the night cloudy, temporarily overcast with showers. The maximum afternoon temperatures in Bohemia reached 30.1 �C, in Moravia 31.0 �C. The average daily precipitation amount in Bohemia was 17.6 mm, in Moravia 5.3 mm. On 3 August the whole territory had almost clear to cloudy weather, temporarily overcast with showers or local rain. The maximum afternoon temperatures reached 22.6 �C in Bohemia and 25.7 �C in Moravia. The average daily precipitation amount in Bohemia was 6.7 mm, in Moravia 1.2 mm.

During this period the stations Lom and Teplice in the Ústí and Labem Region registered the concentrations exceeding 180 μg.m^-3 for three hours, however they decreased very quickly. In connection with the expected transition of the cold front lower values of ozone concentrations were predicted for the following day, without the exceedance of the alert threshold limit. The conditions for the announcement of the warning signal were not fulfilled.

Tab. II.5.1 Overview of the periods with air temperatures above 30 �C for 2 or more days, and of the respective measured maximum ground-level ozone concentrations

Tab. II.5.2 The overview of O₃ concentrations above 180 μg.m^-3 lasting 3 hours and more

Fig. II.5.1 Average daily air temperature, its long-term normal and daily sum of precipitation, Prague-Libuš, 1.1.–28.2.2009

Fig. II.5.2 Average daily air temperature, its long-term normal and daily sum of precipitation, Prague-Libuš, 1.11.–31.12.2009

Fig. II.5.3 Average hourly NO₂ concentrations at the station Prague 2-Legerova, 1.1.–28.2.2009

Fig. II.5.4 Average hourly NO₂ concentrations at the station Prague 2-Legerova, 1.10.–31.12.2009

Fig. II.5.5 Average daily PM₁₀ concentrations at selected stations, 1.1.–28.2.2009

Fig. II.5.6 Average daily PM₁₀ concentrations at selected stations, 1.11.–31.12.2009

Fig. II.5.7 Course of maximum daily air temperatures, their normals and daily sums of precipitation at the station Prague-Libuš. Occurrence of ozone concentrations exceeding 180 μg.m^-3 in the territory of the Czech Republic, 1.4.–30.9.2009

Fig. II.5.8 Spatial distribution of maximum daily concentrations of ground-level ozone in the territory of the Czech Republic, 1.8.–3.8.2009