AN AIR QUALITY STUDY FOR GREECE WITH THE MM5/CAMx MODELLING SYSTEM

Transcription

1 AN AIR QUALITY STUDY FOR GREECE WITH THE MM5/CAMx MODELLING SYSTEM Katragkou E. (1), I. Kioutsioukis (1), A. Poupkou (1), I. Lisaridis (1), K. Markakis (1), S. Karathanasis (2), D. Melas (1), D. Balis (1) (1) Aristotle University of Thessaloniki, Laboratory of Atmospheric Physics, PO Box 149, 54124, Thessaloniki, Greece, (2) Region of Central Macedonia, Directorate of Environment and Land Planning, Thessaloniki, Greece ABSTRACT In the framework of the PROMOTE project the Laboratory of Atmospheric Physics (LAP) has developed an operational forecasting system which provides meteorological and air quality forecasts for a domain covering Greece. The air quality forecasting system operates with the chemical transport model CAMx driven by the meteorological mesoscale meteorological model MM5. Emissions used so far in the operational runs include gaseous pollutants of biogenic and anthropogenic origin. Compilation of an improved emission inventory including additional gaseous species and particulate matter is accomplished. In this work we present results of the LAP air quality modelling system for the year 2006 focusing on ozone and results of a case study to test the new emission inventory including particulate matter and additional gaseous species. The model results are validated with observations from the Monitoring Network of the Greek Ministry of Environment and the Region of Central Macedonia, Directorate of Environment and Land Planning. THE OPERATIONAL MODELLING SYSTEM The operational regional air quality model simulations were performed with the Comprehensive Air quality Model with extensions (CAMx) version CAMx run operationally with coarse grid spacing over Greece in a spatial resolution of 10x10 km The domain s vertical profile contained 5 layers of varying thickness. Layer 1 was 50 m deep while subsequent layer depths increased with height. The uppermost layer extended to about 2.5 km. A more detailed description of the model set up is given in [3]. The meteorological fields were derived from the MM5 prognostic meteorological model PSU/NCAR mesoscale model (MM5 version 3.7). The model domain covered the Balkan area (55x55 grid points with 30 km resolution), the second domain covered Greece (nested domain with 121x121 grid points and 10 km resolution). The vertical profile contained 33 vertical layers extending to 18.5 km. Anthropogenic and biogenic emissions were compiled for a coarse domain covering Greece (110x110 cells, 10x10 km). Emission data for gaseous pollutants (NMVOC, NOx, CO) were estimated for different anthropogenic emission source sectors such as the transport, power plants, the industrial and the central heating sector. Anthropogenic emissions of the neighbouring countries (Albania, Bulgaria and Turkey) were taken from the EMEP emission database. Diurnal biogenic emissions for Greece and neighbouring countries were calculated for every month of the year following the EMEP/CORINAIR methodology [2]. All emissions were ejected in the first model level. The boundary concentrations of the photochemical model are predictions of the European scale Chemistry Transport Model EURAD-CTM ( Proc. Envisat Symposium 2007, Montreux, Switzerland April 2007 (ESA SP-636, July 2007)

2 unikoeln.de/index.html/modell/ctm/index.html). Evaluation of the modelling system has shown that it performs well regarding O 3 and NO 2 while CO concentrations are systematically underestimated. More reliable are daily forecasts for days when it is not raining [3]. In order to examine whether the modeled species exhibit typical seasonal variation we calculated monthly means of ozone using the results produced from last year s runs. Since ozone is a typical photochemical pollutant we would expect a strong seasonal cycle through a year. In Figure 1 are shown the calculated monthly means for ozone for the period February 2006 January It is clear that ozone values are higher during summer months with higher (>70 ppb) concentrations in the surroundings of the two greater urban agglomerations: Athens and Thessaloniki. Concentrations during winter months are as expected lower with minima over industrial/urban regions. A noticeable feature especially during the winter months are the generally higher ozone mixing ratios over the sea in comparison to those over land, probably due to lower deposition rates. IMPROVEMENTS OF THE MODELLING SYSTEM The operational modelling system has been further developed and its performance has been validated with data from the Monitoring Network of the Greek Ministry of Environment and the Region of Central Macedonia, Directorate of Environment and Land Planning. The improvements accomplished so far can be summarized as follows: The emission inventory has been recompiled to include more gaseous aerosol precursors (sulfur dioxide and ammonia). A bottom-up methodology to calculate emissions of particulate matter (PM10) has been developed and applied over Greece with a resolution of 10x10 km and 2x2 km over greater Athens and Thessaloniki areas. The raw data were delivered from different national and European resources. The detailed methodology and validation of the emission inventory is described in detail in [1]. Point sources were introduced to substitute power plant emissions which were so far treated as surface area sources. Emission heights reach up to the fourth vertical level (~200 m). Two nested domains with finer grid resolution (2x2 km) were added over Athens and Thessaloniki greater areas additionally to the master domain over Greece. Meteorological input and emissions are available with finer resolution for the nested domains. The chemistry mechanism invoked was Carbon Bond version 4 (CB4). This mechanism includes 117 reactions 11 of which are photolytic - and up to 67 species (37 state gasses, up to 18 state particulates and 12 radicals). The domain s vertical profile contains 15 layers of varying thickness. Layer 1 is 22 m deep and subsequent layer depths increases with height. The uppermost layer is 1.5 km thick and extends to about 8 km. The latest version of CAMx has been used (v4.40) for a 5-day case study May Model results of the first two days are not shown here, were necessary though, for the initialization of the model. The days from 27 to 29 May 2003 can be considered as typical early-summer weekdays. The results presented in this work are shown in Figure 2. The upper left panel shows modelled and measured SO2 mixing rations for an urban-traffic station in Athens, Patision. Measurements exhibit almost no diurnal variation. On the contrary model results, although they have comparable mean SO2 values with measurements (Table 1) they exhibit a pronounced diurnal variation with higher mixing ratios around morning rush hours (~ 8:00) with maxima modified according to meteorology. Measured SO2 in Galatsi is relatively lower reflecting typical urban-background pollution levels.

3 Figure 1. Monthly means of Ozone calculated for the past year by the operational modelling system CAMx/MM5

4 Figure 2. Time series of PM10 and SO2 for a 3-day case study with the improved modelling system MM5-CAMx

5 The model seems not to reproduce this feature, actually modelled mean SO2 values and diurnal patterns for Patision and Galatsi are quite similar (they are geographically quite close to each other). For Ag.Sofia station in Thessaloniki, a typical street canyon station, diurnal variations are both in observed and modelled time-series evident, however not correlated. Measured mixing ratios peak around noon as expected, while modelled mixing ratios in very early morning hours. Nevertheless, there is a good agreement between mean calculated and measured values (Table 1). Measured SO2 in Kalamaria station (suburban) mixing ratios remain almost unchanged during the three days and the model calculations more or less follow this behaviour, underestimating SO2 somewhat. An overall conclusion concerning SO2 is that mean modelled and observed values are in fairly good agreement, correlation though seems to be a more problematic issue. Modelled pollutant daily variations seem to be more affected by the emission temporal profiles and so the temporal disaggregation should be handled with more caution. In the last 4 panels of Fig. 2 we show the modelled and measured PM10 concentrations in four stations: Likovrisi (sub-urban), Ag.Paraskeui (background, suburban), Zografou (background, suburban) and Panorama (suburban). Evidently model performs better in background suburban stations (Ag. Paraskeui and Zografou stations) suggesting that urban emissions are rather underestimated. Table 1. Comparison of mean 3-day SO2 and PM10 for the period 27-29May 2003 Station, Pollutant Mean values, observed Mean values, modelled Patisia, Athens, SO2 (ppb) Galatsi, Athens, SO2 (ppb) Ag. Sofia, Thessaloniki, SO2 (ppb) Kalamaria, Thessaloniki, SO2 (ppb) Likovrisi, Athens, PM10 (ug/m 3 ) Ag. Paraskeui, Athens, PM10 (ug/m 3 ) Zografou, Athens, PM10 (ug/m 3 ) Panorama, Thessaloniki, PM10 (ug/m 3 ) REFERENCES 1. Markakis K., A. Poupkou, E. Katragkou, D. Melas, (2007), Compilation of an anthropogenic PM10 emission inventory for Greece and the two urban centres of Athens and Thessaloniki, Geophysical Research Abstracts, Vol. 9, European Geophysical Union, General Assembly , Vienna, Austria. 2. Poupkou, A., Symeonidis, P., Lisaridis, I., Pouspourika, E., Yay, O.D., Melas, D., Ziomas, I., Balis, D. and Zerefos, C., (2004), Compilation of an emission inventory for the purpose of studying the regional photochemical pollution in the Balkan Region. In the Proceedings of the Quadrennial Ozone Symposium 2004, Kos, Greece, pp Poupkou A, D. Melas, I. Kioutsioukis, I. Lisaridis, P. Symeonidis, D. Balis, S. Karathanasis, S. Kazadzis, Regional air quality forecasting over Greece within PROMOTE, (2006), European Space Agency, (Special Publication) ESA SP (628).