A synoptic analysis of the meteorological conditions affecting dispersion of pollutants emitted from tall stacks in the coastal plain of Israel

The meteorological conditions affecting dispersion of pollutants emitted from tall stacks in the coastal plain of Israel were analysed according to a synoptic approach. The SO₂ highest concentrations (episodes) measured around the largest power plant were first screened in order to characterize the associated synoptic configurations. Almost all the episodes were found to fall into three synoptic categories, all occurring during the warm season. According to the synoptic classification, the main elements influencing dispersion of pollutants were then analysed: the wind and temperature profiles and estimations of the plume rise and its partial penetration into the stable layer aloft. The following conclusions were reached: (a) horizontal wind shear is absent in the appropriate atmospheric layer; (b) for the shallow Persian trough synoptic category, in which the SO₂ episodes are the most frequent (55% of the total number), the CBL is shallow (450 m) and over two-thirds of the plume volume is expected to penetrate into the stable layer; (c) for the deep Persian trough synoptic category, which is the second most frequent among the episodes (22% of the total number), plume rise would be unobstructed in the deep CBL (900 m). A prediction index defined as the ratio of the frequency of each synoptic category among the SO₂ episodes to its annual frequency was developed. The marked differences obtained in the index values were tentatively explained by the different thermal stratification in the coastal CBL for each synoptic category. The synoptic classification was thus shown to be an efficient tool for predicting spells of SO₂ high concentrations.