Surface Ozone Concentration Variability in Moscow and Kiev

Transcription

1 ISSN , Russian Meteorology and Hydrology, 2010, Vol. 35, No. 12, pp Allerton Press, Inc., Original Russian Text A.M. Zvyagintsev, I.B. Belikov, N.F. Elanskii, I.N. Kuznetsova, Ya.O. Romanyuk, M.G. Sosonkin, O.A. Tarasova, 2010, published in Meteorologiya i Gidrologiya, 2010, No. 12, pp Surface Ozone Concentration Variability in Moscow and Kiev A. M. Zvyagintsev a, I. B. Belikov b, N. F. Elanskii c, I. N. Kuznetsova d, Ya. O. Romanyuk e, M. G. Sosonkin e, and O. A. Tarasova f a Central Aerological Observatory, Pervomaiskaya ul. 3, Dolgoprudny, Moscow oblast, Russia b AOZT Atmosfera, Pyzhevskii per. 3, Moscow, Russia c Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Pyzhevskii per. 3, Moscow, Russia d Hydrometeorological Research Center of the Russian Federation, Bolshoi Predtechenskii per. 9 13, Moscow, Russia e Main Astronomical Observatory, National Academy of Sciences of the Ukraine, ul. Akademika Zabolotnogo 27, Kiev, Ukraine f World Meteorological Organization, 7bis, avenue de la Paix, Case postale No. 2300, CH-1211 Geneva 2, Switzerland Received October 13, 2009 Abstract The comparison is represented of the results of surface ozone concentration measurements in two megalopolises, Moscow and Kiev. A temporal course of ozone concentration and temperature in both cities is close by the shape and is typical of medium-polluted plain stations. In both megalopolises, two maxima are observed within the seasonal ozone concentration variability, in spring and summer, and during the day, a usual ozone concentration maximum (approximately in 2 3 hours after the local noon) and the night one being typical of big cities. An average ozone concentration and an average temperature in corresponding periods are higher in Kiev than in Moscow. Evidently, the summer maximum is associated with photochemical ozone generation processes, and the spring one, with dynamic processes of its transport in the atmosphere. In both megalopolises, the episodes are observed in the warm period under meteorological conditions being unfavorable for the pollutant scattering in the atmosphere when the ozone concentration exceeds the threshold limit value and is dangerous for health. The repeatability of such episodes is the highest one in July August. In Kiev, such episodes are more frequent than in Moscow. An effective statistical model is constructed for both megalopolises in which the observed ozone concentration is represented in the form of regression function of temperature and relative humidity. DOI: /S INTRODUCTION An urgency of the surface ozone concentration (SOC) observations in big megalopolises is associated with the necessity of the air quality control. The unsatisfactory quality of the air in the warm period of the year is almost always caused by exceeding the threshold limit value of ozone [14]. Recently, a number of papers has published dealing with the peculiarities of the temporal SOC course in Moscow region [4, 5, 9, 11, 12] and in Botanical gardens in Kiev [1]. It is demonstrated that this course generally corresponds to the SOC course in midlatitudes at continental rural stations of Western Europe [17, 19] with the peculiarity in the nighttime in Moscow being typical of big cities only [5, 19]. The first SOC observations in Moscow are described in [2], the regular SOC observations have been carried out in woodland park zones of Moscow since 1991 [11] and in Botanical garden of Kiev since 1995 [1]. The SOC monitoring quality in Moscow has become corresponding to the world level since 2002 [4, 5]. This paper considers the comparison of the SOC observation results in rather low-polluted districts of Moscow and Kiev that enables to judge about the regularities in the temporal SOC course in the megalopolises of the countries of Eastern Europe needed, in particular, to estimate the possibility of formation of surface ozone concentration being dangerous for health in big southern cities of Russia where such observations are not carried out. 806

2 SURFACE OZONE CONCENTRATION VARIABILITY IN MOSCOW 807 Fig. 1. Average seasonal diurnal course of (a, b) ozone concentration (ppb) and (c, d) temperature ( C) in (a, c) Moscow in and in (b, d) Kiev in USED DATA In the paper, the hourly average data are used of the stations of Institute of Atmospheric Physics of the Russian Academy of Sciences and of Moscow State University at Vorob evy Gory in Moscow (56 N, 38 E, 190 m above the sea level) [4] for and of the Main Astronomical Observatory of the National Academy of Sciences of the Ukraine at the southern outskirts of Kiev (51 N, 31 E, 120 m above the sea level) for An error of the SOC observations carried out using the optical ozone gas analyzers, Dasibi-1008AN in Moscow and Termoelektron model 49i in Kiev, does not exceed ±2 ppb. Other characteristics of the used observation means are described in [5]. In addition, the observational data are used at the stations of the world meteorological network No (Moscow) and No (Kiev). For comparison, the data are also used of continuous measurements of concentration of ozone and primary atmospheric pollutants (NO, NO 2, and CO) obtained at the rural (background) stations of Western Europe and represented in the archive of the World Data Center on Greenhouse Gases ( as well as in London ( SEASONAL DIURNAL COURSE OF OZONE AND OF PRIMARY ATMOSPHERIC POLLUTANTS Ozone comes to the surface layer due to the vertical mixing which favors its transport from higher tropospheric levels where its mixing ratio is larger; also it is formed as a result of photochemical transformations; ozone is destroyed both during chemical reactions on the Earth s surface ( dry and wet deposition) and during gas- and heterophase reactions in the air [13, 17, 19]. A photochemical ozone generation occurs with participation of so-called ozone s predecessors: nitrogen oxides (NO and NO 2 ) acting as catalysts as well as volatile organic compounds (first of all, from the class of nonmethane hydrocarbons) and carbon monoxide (CO) consumed during chemical reactions. A fraction of stratospheric and photochemically generated ozone is estimated in models. It differs at various altitudes in the troposphere [18]. The SOC dynamics during the year is most fully characterized by the average long-term seasonal diurnal course within which its main peculiarities are most clearly revealed [18]. Such SOC and temperature course for both megalopolises is represented in Fig. 1. In Moscow, among all meteorological variables, the ozone has the strongest relationship with temperature, the smaller one, with relative humidity, still smaller one, with wind speed [9]. Among the physical reasons for the influence of maximum diurnal temperature in the warm period on the maximum diurnal ozone concentration (the latter one determines to a large degree the average daily ozone concentration as well [13]; in the cold period, this influence is clearly weakened), the most clear ones are its relations with the vertical mixing intensity (at small time intervals, up to one month,

3 808 ZVYAGINTSEV et al. the maximum diurnal temperature correlates with temperature difference in the daytime and at the nighttime and, hence, with the intensity of vertical mixing in the daytime) and with the concentrations of ozone s predecessors in the air of both natural and anthropogenic origin participating in photochemical ozone generation. It is clear from Fig. 1 that during the whole year, the average SOC and average temperature in corresponding periods of time are considerably higher in Kiev than in Moscow. To a first approximation, both seasonal and diurnal courses correlate well with the average temperature course. At the same time, the differences are also seen: while the temperature within both seasonal and diurnal courses has only one maximum, the diurnal SOC course maxima are observed before the temperature maximum and after it and there is no analog to the nighttime SOC maximum within the diurnal temperature course. The seasonal and diurnal SOC variations in both megalopolises are similar by shape. Within the seasonal SOC variability, in spring and summer, two localized maxima are observed of average daily and maximum diurnal SOC. In both megalopolises, two maxima are observed during the day: a usual SOC maximum observed approximately in 2 3 hours after the local noon and pseudomaximum at the nighttime. Such nighttime SOC pseudomaximum is observed in all big European cities, is absent at all rural and distant stations, and is associated with the nighttime ozone destruction rate decrease due to the reduction of anthropogenic emissions of nitrogen monoxide (NO) [17, 19]. It is clear from Fig. 1 that the nighttime maximum is less pronounced in Kiev than in Moscow that is evidently caused by the smaller level of anthropogenic emissions here. According to the classification [18], the seasonal SOC course in both megalopolises can be considered as typical of medium-polluted (by ozone s predecessors) plain stations. In this classification, the pollution level is estimated on the basis of ratio of maximum hourly average SOC values in spring and summer maxima. The ratio of maximum hourly average SOC values in summer to their values in spring in Moscow and Kiev is less than the same ratio at rural stations in the north of Germany, in Poland, etc., but is higher than the ratio at the stations in the south of Germany, in the north of Italy, in Hungary, etc. Evidently, the summer ozone maximum is associated with its photochemical generation taking place in the presence of sufficient values of solar radiation flux and concentration of ozone s predecessors [18, 19]. The spring SOC maximum is sooner associated not with photochemical processes but with the seasonal peculiarities of its transport in the atmosphere. The diurnal nighttime SOC pseudomaximum is observed on rather small territory around big cities (the typical size is several tens of kilometers). Episodes with increased SOC values in the warm period are observed on the territories with the typical size of several hundreds of kilometers [8, 10] that indicates the influence of general regional level of ozone s predecessors on the SOC. It is interesting to compare the averaged seasonal diurnal SOC course and concentrations of ozone s predecessors in big cities (Figs. 2 and 3; for Kiev, such data are absent). The data for London are given for North Kensington Chelsea district being one of the most ecologically pure regions and situated near the center of London. Automated observations of pollutant concentration in London have been carried out since 1993 and seem to be reliable enough. It is clear from the comparison of Figs. 2 and 3 that average concentrations of NO and NO2 in North Kensington Chelsea district in London correspond to those observed near Moscow State University (MSU) in Moscow, and for CO, considerably less. As well as in Moscow [4], concentrations of NO, NO 2, and CO in different districts of London differ by several times, the ozone concentration at the levels of more than 50 ppb, by not more than 1.5 times; the shape of its seasonal diurnal course in different districts is similar. The similarity of the shapes of seasonal diurnal course of primary atmospheric pollutants in Moscow and London represented in Figs. 2 and 3 indicates evidently that they are similar to those observed in other big cities of Europe, the difference is only in the concentration values. Moreover, the seasonal and diurnal variations of concentration of ozone, NO 2, and CO at European background stations have the analogous shape as well. The concentration of primary pollutants here is less than that given in Figs. 2 and 3 by from several times (for example, in Payerne in Switzerland) to tens of times (Kosetice in Czech Republic). The small differences in the seasonal diurnal course are determined both by the intensity of local and regional emission sources and, not to a lesser degree, by the peculiarities of meteorological conditions, in the first place, by the vertical mixing in the atmospheric boundary layer. The comparison of seasonal and diurnal variations of concentration of considered minor gas atmospheric components at different observation points reveals that their diurnal course in Moscow, Kiev, and London is evidently caused to a considerable degree by the vertical mixing, one of the most important processes for the scattering of primary pollutants. The above does not rule out that the photochemical ozone generation process becomes dominant in the warm period at infrequent meteorological conditions being unfavorable for the scattering of atmospheric pollutants. Due to relatively small chemical activity and, therefore, due to the long existence time (about one month), CO is considered to be an effective marker of main anthropogenic emissions. Seasonal and diurnal

4 SURFACE OZONE CONCENTRATION VARIABILITY IN MOSCOW 809 Fig. 2. Average seasonal diurnal course of concentration of (a) ozone (ppb), (b) NO (ppb), (c) NO 2 (ppb), and (d) CO (ppm) in Moscow (MSU area) in Fig. 3. The same as in Fig. 2 for London, North Kensington Chelsea district, variations of concentrations of CO and NO x (the sum of concentrations of NO and NO 2 ) in Moscow in every separate year are qualitatively close to the average ones represented in Fig. 2 but slightly differ from each other by the time of the extrema, first of all, of the maximum at the late fall early winter. During the year, two minima of average diurnal concentrations of NO x and CO are observed: in the warm period, from May to July, caused by the removal of pollutants in the daylight from the atmospheric boundary layer due to the intensive vertical mixing, and in the cold period, from October to January. During the day from February to October, the minimum concentrations of NO x and CO are observed at the nighttime (00:00 06:00) and in the daytime (12:00 18:00). The interval between the morning and evening maxima is proportional to the duration of the daylight. In fall, the time interval between the maxima decreases to hardly discernible one and in the period up to January February only one maximum in the daytime and one minimum at the nighttime are observed within the diurnal course of concentrations of NO x and CO. Owing to the seasonal course of

5 810 ZVYAGINTSEV et al. radiation balance of underlying surface being the reason for the stable stratification in the cold season and for the unstable one, in the warm period, and assuming the approximate constancy of pollutant emissions during the year, one should expect the only maximum of average diurnal concentrations of NO x and CO in the cold period and the only minimum, in the warm period. The results of observations on the concentrations NO x and CO correspond to exactly such seasonal course, for example, at the rural stations of Western Europe near which considerable pollutant emissions are absent. At such stations (the Netherlands, Switzerland, etc.) according to the data of the World Data Center on Greenhouse Gases, the diurnal course of concentrations of NO x and CO is small or practically absent, the only seasonal maximum of average diurnal concentrations is considerably lower than in Moscow and is observed in the cold period and the minimum, in the warm period. Therefore, probably, a small winter minimum of concentrations of NO x and CO in Moscow is caused by decrease in the intensity of the motor transport motion in winter period. EPISODES OF HIGH OZONE CONCENTRATION In both megalopolises in the period from May to the early October, the episodes are observed under unfavorable (for the scattering of pollutants) meteorological conditions when the ozone concentration exceeds the maximum permissible value (MPV) and is dangerous for health. In Russia and the Ukraine, such norm is the single (averaged for 20 minutes) ozone concentration being equal to 160 g/m 3 (corresponds to approximately 80 ppb [17]) [3]. In Western Europe, 180 g/m 3 is considered to be the critical ozone concentration [15] at which, according to the legislation, the authorities must inform the population that corresponds approximately to the level of Russian MPV since the background SOC there are 20 g/m 3 higher than in Moscow region [8]. The World Health Organization recommends to Europe to consider the concentration of 100 g/m 3 averaged for eight hours as the safe ozone level [14]. The highest SOC in Moscow was registered in 2002 [7]: average numbers for one and eight hours reached 259 and 183 g/m 3, respectively. The recurrence of such episode is the highest in July August and, by all appearances, there are more of them in Kiev than in Moscow. In Moscow region, such episodes during last 12 years have been observed approximately once per two years (in particular, there were no such episodes in 2008); in Kiev, they were observed in 2007 and In particular, in 2008, there were four episodes in Kiev, all of them were registered in August, the average SOC for one and eight hours amounted to 182 and 159 g/m 3, respectively. MODELS OF TEMPORAL COURSE OF SURFACE OZONE For both megalopolises, rather effective statistical models are constructed representing the observed SOC as the regression function of temperature, relative humidity, average wind speed and its direction in the atmospheric boundary layer [9, 11]. The improved version of such model for Moscow is given in [6]. For the maximum SOC averaged for one hour C max (d) (ppb) in Moscow [6] and Kiev (the subscripts M and K, for Moscow and Kiev, respectively), the model taking account of temperature and relative humidity (wind parameters turned out to be statistically insignificant) has the following form: C maxm (d) =C max0m (d) C max (d 1) + ( cos(2 d/365)) T(d) + + ( cos(2 (d 47)/365)) RH(d); C maxk (d) =C max0k (d) C max (d 1) + ( cos((d 8)2 d/365)) T(d) + + ( cos(2d /365)) RH(d), where C max0 (d) is the norm for the maximum SOC averaged for one hour (ppb) depending on the Julian day d ; C max (d 1) is the deviation of the SOC value at the previous day d 1 from the norm; T(d) and RH(d) are the deviations from the norm of the values of maximum temperature averaged for one hour ( C) and minimum relative humidity averaged for one hour (%) at day d. The presence of periodic component in the coefficients for T(d) and RH(d) indicates the different influence of meteorological variables on the SOC in different seasons. Thus, the largest influence of temperature anomalies is observed in summer and of relative humidity anomalies, in winter; on the contrary, the influence of temperature anomalies in winter and of relative humidity ones in summer is insignificant. The norms for the maximum SOC averaged for one hour in Moscow [7] and Kiev depending on the Julian day are expressed through the relationships (1) C max0m (d) = cos((d 154)2 /365) + 1.9cos((d 46)4 /365) + 4.8cos((d + 21)6 /365); C max0k (d) = cos((d 162)2 /365) + 3.8cos((d 70)4 /365) + 2.7cos((d + 12)6 /365). (2)

6 SURFACE OZONE CONCENTRATION VARIABILITY IN MOSCOW 811 Expressions for the norms of maximum temperature and minimum relative humidity have the same form. According to (2), the main difference in the norms of the maximum SOC averaged for one hour for Moscow and Kiev is in the difference of the first terms in the right part of equations: in the second equation of (2) for Kiev, this term is approximately 10 ppb larger than in the first one for Moscow that is demonstrated in Fig. 1. The difference in the SOC norms in Kiev and Moscow is almost constant during the whole year. Model coefficients for C max (d 1), T(d), and RH(d) in (1) for Moscow and Kiev are similar enough both by the quantity and by the seasonal dependence. Quantitatively, they correspond to the analogous parameters computed for the stations of Western Europe [16]. Thus, the temperature increase by 1 C inthe warm season results in the SOC increase in both cities approximately by 1.5 ppb, and in the cold season, it practically has no effect. In the cold season, the relative humidity decrease by 5% also results in the SOC increase approximately by 1.5 ppb, in the warm season, the effect is considerably smaller. The presence of two maxima in the diurnal course of SOC and of only one maximum in the temperature course explains, in particular, the fact that in (1) not the values of temperature and relative humidity themselves are used but their deviations from the norm: using only the values of meteorological variables it is impossible to obtain two model SOC maxima during the year. The use of the deviations of meteorological variables from their norms in the regression relationship enables to make the model more effective. The models based on relationships (1) and (2) give the satisfactory results at the quantitative SOC description in different periods of the day, first of all, for the maximum diurnal values [6]. Determination coefficients of the SOC in the models described with relationships (1) and (2) are within the range of for both megalopolises. One of the shortcomings of the SOC model described with (1) is the underestimation of model results in the warm season in both megalopolises in the episodes of surface ozone concentration exceeding the MPV. The construction of the models separately for the warm season improves their quality for this period (in so doing, in particular, the temperature influence becomes more significant) but not so much to increase considerably their determination coefficient. CONCLUSIONS As a result of the comparison of the temporal SOC course in Moscow and Kiev, the similarity of their seasonal diurnal course is demonstrated. The surface ozone concentration and the temperature in Kiev in corresponding periods of time are usually higher than in Moscow. For both megalopolises, two maxima are observed within the seasonal SOC variability, in spring and summer. During the day in both megalopolises, a usual ozone concentration maximum (approximately in 2 3 hours after the local noon) and the night one being typical of big cities are registered. The seasonal SOC course in both megalopolises is analogous to the seasonal course at the European medium-polluted plain stations. The summer SOC maximum is evidently associated with photochemical processes of ozone generation and the spring one, with dynamical transport processes in the atmosphere. The recurrence of episodes with the SOC exceeding the maximum permissible value and being dangerous for health is the highest in July August. In Kiev, such episodes were registered more frequently than in Moscow during the observational period. Therefore, one can expect that in the big megalopolises in the south of Russia (Volgograd, Rostov-on-Don, etc.) as well, the episodes with the SOC exceeding MPV are observed more frequently than in Moscow. For both megalopolises, the temporal SOC course can be described effectively enough in the form of statistical model representing the observed ozone concentration as the regression function of temperature, relative humidity, average wind speed and its direction. ACKNOWLEDGMENTS The work was supported by the Russian Foundation for Basic Research (project ofi_ts). REFERENCES 1. O. B. Blyum, I. V. Budak, V. A. Dyachuk, et al., Surface Ozone in Kiev. Conditions of Its Generation and Runoff, Trudy UkrNIGMI, No. 250 (2002) [Trans. Ukrainian Research Institute of Hydrometeorology, No. 250 (2002)]. 2. A. S. Britaev and G. P. Faraponova, Peculiarities of Ozone Concentration Distribution in Moscow, in Atmospheric Ozone (Transactions of the 6th All-Union Symposium) (Gidrometeoizdat, Leningrad, 1987).

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