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Permanent increase of the subsonic aviation flights and attempts to develop high-speed civil transport (HSCT) necessitate an assessment of their possible environmental impa,cts. To evaluate global aviation effects, it is important to know the role of the chemical transformations inside an a•rcraft plume taking into account heterogeneous reactions. The goal of this work is to model the principal physical and chemical processes occurring inside an aircraft exhaust plume. A new box model which calculates 41 relevant O•, HO•, NO•, C10•, BrOw, SO•, •nd HC species and includes the possible heterogeneous reactions on the combustion aerosol and ice contrail particles is proposed. The simplified descriptions of the aircraft plume dilution and ice contra.il form,xtion are described. The tra. nsformations inside the aircraft wake a, re presented for the trajectories of the exha.ust product motions at the levels of 200 a. nd •00 mb•r calcula.ted for the particular atmospheric conditions on April 25, 1986. The following problems are discussed: the ozone response at these altitudes, the oxidation ra.te of NOz a. nd SO2, the role of the heterogeneous reactions on the combustion a. erosol and contrail particles, and the possibility of ice and nitric a, cid trihydrate (NAT or I[NOa•3H20) particle formation inside the wake. The model results a. re in agreement with available experimental data for NO, NO2, HNOa, HNO2, and SO2. Ana.lytical expressions are proposed to evaluate the oxidation r•tes of NOr and S02 in the aircraft wake. The local ozone response is small (between 0.6% a,t 200 mb and -0.1% at 100 rob). Possible future investigations are proposed. Introduction The impact of the aircraft. exhaust products in the stratosphere was tlm s•bject of intensive studies in the 1970s [Johnston, 1971; Climatic Impact Assessment Program (CIAP), 1975; llidalgo and Crutzen 1977]. It was concluded that the imprint of aircraft. NO•.(=NO + NO2) on the ozone layer is a strong function of the altitude of injection. Below approximately 13-14 kin, methane-NO,• reactions produce Oa; above this level, stratospheric ozone is depleted due to the fast reactions of O• and O(3P) with NO and NOe. So it is very important to simulate the possible exchange between the troposphere and stratosphere to obtain reasonable esti-•Now a• However, progress in atmospheric chemistry since the time of the first assessments has revealed a different and still changing view of the atmospheric effects of stratospheric aircraft flights. A few years ago two-dimensional (2-D) models gave up to 1.0% ozone column depletion for different scenarios of aircraft injections and geographic locations, using homogeneous reactions only [Johnston et al., 1989; Douglass et al., 1991; Prather et al., 1992, Chap.5]. It was shown that the Oa layer response was greater for the larger NO•: emission index (EI) (which is menured in grams of NOa, per kilogrmn tirol) and higher cruise altitudes. The factor of 2 difference in the ozone response between these studies is not surprising and "can be u...

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Abstract.The role of inorganic bromine compounds in the chemistry of the midlatitude lowermost stratosphere is examined. Model studies are perfomed using a chemistry box model. Special emphasis is layed on investigating the implications of bromine chemistry on the atmospheric effects of subsonic aircraft NOx emissions. The simulations suggest that the presence of bromine constituents leads to an effective denoxification, an activation of HOx, and a significant ozone depletion in the background lowermost stratosphere. Bromine chemistry has the potential to induce large increases in the modeled ozone production caused by aircraft NOx emissions in the lowermost stratosphere. The modeled effect strongly depends on the availability of inorganic bromine compounds, on aerosol loading, and on the NOx background concentration. The hydrolysis reaction of BrONO2 on sulfate aerosols and the reaction of BrO with HO2 appear to be the key reactions driving the simulated impact of bromine chemistry on the aircraft-induced ozone changes.