Some observational and modeling evidence of long-range transport of air pollutants from Europe toward the Israeli coast

The present paper reports results of a study that attempted to elucidate th e factors causing relatively high levels of particulate sulfate that have f requently been observed over central Israel. Aircraft research flights were performed some 70 km west of and parallel to the Israeli coastline during September 1993 and June 1994. Comparison between the two measurement period s revealed a distinctive difference between the two different sampled air m asses. While both air masses were nearly homogeneous throughout the measure ment period and along the 180 km flight path, the air mass sampled in Septe mber 1993 was much "cleaner" than the air mass sampled during June 1994. Th e concentrations of the air pollutants measured during the 1993 campaign av eraged 0.7 +/- 0.4 parts per billion by volume (ppbv) SO2, 1.0 +/- 0.6 ppbv NOgamma, 39 +/- 7 ppbv O-3 and 38 +/- 7 nmol/m(3) particulate sulfate, whe reas in the second period the levels averaged 3.0 +/- 1.0, 3.9 +/- 1.8, 48 +/- 9, and 108 +/- 63, respectively. These results suggest that the two air masses traveled different paths before reaching the eastern Mediterranean region. Further examination of the air mass sources and transport were perf ormed using the Regional Atmospheric Modeling System for meteorological sim ulations and the Hybrid Particle and Concentration Transport Package for di spersion modeling. The model simulation showed that during the 1993 measure ment period, the pollution sources in southern Europe and the Balkans did n ot effect the eastern coasts of the Mediterranean, while the synoptic condi tions and simulation results for the June 1994 period indicated that the wi nds over the eastern Mediterranean tended to be northwesterly and thus forc ing the polluted air masses toward the coast of Israel.