A Study On The Influencing Factors Of Ozone Depletion In The Dead Sea Area

As an important oxide that can determine the oxidative properties of the atmosphere,ozone has drawn attention from the researchers.In 1997,Herbestreit et al.observed frequent ozone depletion events（ODEs）episodes in the Dead Sea region at mid-latitudes for the first time during the measurement campaign,which breaking the inherent understanding of the ODEs based on Arctic ODEs studies.In this paper,the WRF model and CMAQ model are used to simulate the ODEs in the Dead Sea area.After obtaining reasonable simulation results in comparison with the actual observations of Holla et al.,the influence of physical transport process,the heterogeneous decomposition of BrONO₂ and the iodine chemistry to the ODEs in Dead Sea are further analyzed.The results suggest:（1）Two heterogeneous reactions which related to the bromine cycling can affect ODEs in the Dead Sea area.The bromine explosion mechanism plays a prior role during the ODEs in such a rich bromine environment like Dead Sea.The result of the simulation case that lacks the reaction of the bromine explosion mechanism shows,although the bromine can released into the boundary layer through the photochemical reaction,than cause the depletion of ozone and affect its daily diurnal.Beacuse of the low mixing ratio of bromine in the boundary layer,it cannot cause the occurrence of ODEs.（2）The heterogeneous decomposition of BrONO₂ has a relatively small impact to the ODEs in the Dead Sea aera,which is mainly reflected in the rate of ozone depletion and the rate of BrO generation..The result of scenario case which lacks the heterogeneous decomposition reaction shows,due to the lack of the mechanism for bromine circulation between aerosols and boundary layed,the generation of BrO is slower and the depletion of ozone is also much slower.However,due to the existence of reversible reaction of Br and NO2 which produces Br NO2,this heterogeneous reaction does not have much impact on the overall mixing ratio of BrO and the occurrence of ODEs.（3）The influence of the physical transport process on the ODEs is reflected in two aspects:the transportation of humid air mass and the influence of meteorological factors（wind speed）.The moist air mass can provide more reaction places for heterogeneous reactions,accelerate the reaction rates,and promote the consumption of ozone,leading to the ODEs.Weak winds blown from the Mediterranean can cause vertical circulation over the Dead Sea and promote the continuous depletion of ozone in the air mass above the Dead Sea,which finally leading to the occurrence of ODEs.（4）The impact of iodine on ODEs in the Dead Sea area is mainly manifested in the competition with bromine.The reaction of iodine and nitrogen oxides hinders the circulation of bromine between atmosphere and aerosols,and also the generation of BrO.However,because of its low content in the environment,iodine will not show any obvious effect..