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On some ozone studies: comparison of model results and measurements over the territory of Bulgaria
K. Georgiev, E. Donev
Institute for Parallel Processing of Bulgarian Academy of Sciences, Acad. G. Bonchev str., Bl. 25-A, 1113 Sofia, Bulgaria
Faculty of Physics of Sofia University, 5, J. Bourchier Blvd., 1126 Sofia, Bulgaria
TM5 model is used to estimate the ozone pollution over the territory of Bulgaria and surrounding countries for year 2000. The model output results are compared with measurements done by two stations in Bulgaria. The rest of the paper is organized as follows. In section 2 some basic principles and description of the TM5 model are presented. Section 3 is devoted to the short description of the measurement stations and their parameters. TM5 output results and comparisons with the measurements can be found in section 4.
Measurements from two measurement stations are used for the comparisons reported in this paper. First station is located almost on the see level (at an altitude of 5 m. above see level) on the Black See cost, near the town of Ahtopol. This station is far from the industrial zones but at the same time is very much depend on the breeze circulations of the wind. As is reported in some papers the breeze circulations lead to recirculation of the air which is reach of ozone of the previous days. The last process can lead to dangerous concentrations of ozone in the areas closed to the see.
The second station is located in the mountain (Rodopi mountain; at an altitude of 1570 m above see level). The location of this station gives the possibility to make estimation of the background values of the ozone in this part of Europe. Like the first station, it is far from anthropogenic precursors of ozone. At most time there are winds from the north and the west directions at the location of the station.
The TM5 model setup is ideally suited for measurements campaigns (Krol et al., 2005). We analyze the ozone measurements that were made in the both Bulgarian stations mentioned above for the year 2000 on monthly mean base. Ahtopol station (see Tabl. 1 and the corresponding figure)
The comparisons between measurements done at this stations and the TM5 output show that the model results underestimate the measurements during the winter, spring and autumn, and overestimate the measurements during the summer period. The model results follow well the tendency in the increasing and decreasing of the values of the ozone concentrations but the differences in percent are relatively high for some months. It seems that use of the wind data measurements and other meteorological parameters as boundary heights, etc. (not used in this study) are very important for the validation of the model results. Rojen station (see Tabl. 2 and the corresponding figure)
Comparisons between measurements done at this station and the TM5 output, show, that the model results underestimate the measurements during the whole year. The underestimate is essential during the winter months, is decrease during the spring and autumn, and it is negligible during the summer period. The model results follow well the tendency in the increasing and decreasing of the values of the ozone concentrations. The conclusions made above about the influence of some meteorological parameters which are not taken into account in this study seem to be true for this station too. Nevertheless there are some differences between the measurements and the model results it can be concluded that the obtained critical levels of the ozone concentrations for the area of the Rojen station are dangerous for trees. The calculated AOT40 indexes are more than two times more than the limit values for forests.
Table.2. Comparisons between measurements and TM5 output results for Rojen station
The first author was partially supported by the Joint Research Center, Ispra, Italy and the NATO Project: "Impact of Climate Changes on Pollution Levels in Europe".