The aim of the study is to analyse the connection between meteorological elements and the concentrations of the main air pollutants at Szeged.

The data basis consists of daily values of 9 meteorological and 8 air pollution parameters for the summer (June, July, August) and winter (December, January, February) months for the five-year period 1997-2001. The meteorological parameters are: mean air temperature [T_mean (°C)], maximum temperature [T_max (°C)], minimum temperature [T_min (°C)], diurnal temperature range [DT (°C)], relative humidity [RH (%)], irradiance [I (W m^-2)], wind speed [WS (m s^-1)], wind direction [WD (°)] and atmospheric pressure [P (hPa)]. The air pollution parameters are: carbon monoxide [CO (mg m^-3)], nitric oxide [NO (ug m^-3)], nitrogen dioxide [NO₂ (ug m^-3)], total suspended particulate [TSP (ug m^-3)], sulfur dioxide [SO₂ (ug m^-3)], ozone [O₃ (ug m^-3)], maximum ozone concentration during the day [O_3max (ug m^-3)] and the NO₂/NO ratio.

The determination of characteristic weather types affecting the region of Szeged during the summer and winter months is achieved by using factor and cluster analysis. First factor analysis is applied in order to reduce the 9 initial meteorological parameters to a smaller number of factor loadings, which can explain the basic system of the meteorological parameters for Szeged. Then, cluster analysis is used for the time series of the factor loadings, in order to group objectively days having similar weather conditions. In the clustering procedure the hierarchical technique with „average linkage” method is used. Hereafter, for each of the derived clusters of days, averages of all meteorological and air pollution parameters are calculated. In this way, connection between weather conditions and concentrations of the considered air pollutants are revealed.