Frequency and extent of ozone destruction episodes over the Dead Sea, Israel

Abstract

A previous study performed at the Dead Sea during the summer (J. Geophys. Res. 106 (2001) 10375) has shown frequent ozone depletion episodes, when the mixing ratio of ozone was reduced to less than 5 ppb. These episodes were accompanied by the presence of high BrO levels (up to a level above 150 ppt). In order to establish the temporal and spatial extent of ozone depletion and subsequently indirect evidence of BrO formation, continuous ozone measurements were performed at three sites along the Dead Sea for a 14-month period starting from February 2001. The results indicated that extensive ozone depletion effects occur along the entire region of the Dead Sea basin during all periods of the year. The depletion effects were more pronounced in the southern areas (mid and south sites) than the north site. Since ozone depletion occurs with higher frequency in the south closer to the evaporation ponds and saltpans, it appears to be related to a higher sea-salt aerosol concentration in that region. Ozone depletion effects were also observed during a short-term study performed at a site situated approximately 1 km west and 400 m above the Dead Sea. Further, the ozone depletion effects appear to be more pronounced during summer than winter times. Additionally, these effects are prevalent during all periods of the year. Comparison of the Dead Sea data with ozone levels measured simultaneously at Beer Sheva, a site some 60 km west and outside of the Dead Sea Valley, demonstrates the extent of the ozone depletion. Further, while the Beer Sheva site showed the typical diurnal ozone cycle with ozone peaking at midday, the Dead Sea sites show a reverse situation and had decreased midday levels during the summer period. The present study indicates that ozone depletion events, and hence BrO production, occur all along the entire Dead Sea Valley and extend to a significant distance vertically and horizontally away from the water level.