Bromine compounds contribute significantly to stratospheric ozone depletion. The total BrO columns measured from ground and satellites however are too large to be explained by the transport of organic bromine into the stratosphere. Therefore a UV/visible spectrograph for balloon-borne measurements of vertical profiles was developed. This instrument was deployed in three flights measuring the stratospheric profiles of bromine oxide, ozone and nitrogen dioxide between 9 and 40 km height. The average mixing ratio of BrO above the summit height was determined as 15±2pptv accordingly in León (autumn, 42°N, 30km) and Kiruna (winter, 68°N, 30km) and to 16±2pptv in Gap (summer, 46°N, 40km). Total BrO columns were determined by the evaluation of spectra from the satellite-borne experiment GOME using an already existing evaluation method [Hegels, 1998] (León: 5±1 1013 molec. cm-2, Kiruna: 7±2 1013 molec. cm2). Comparison with the stratospheric columns measured with the balloon experiment (León: 2.3±0.4 1013 molec.cm-2, Kiruna: 4.1±0.61013 molec.cm-2) indicate a tropospheric contribution to the total column of 1.5±0.6pptv BrO in León and Kiruna. A photochemical box model was developed to determine the total bromine content of the stratosphere. Filterradiometer measurements provided the means to validate a radiation transport model which was used to calculate photolysis frequencies. These and the measured concentrations of BrO, NO2 and O3 were used as parameters in the box model, resulting in a total inorganic bromine content of 19±3pptv in 32km height for León. The current understanding of the photochemistry of bromine oxide [Lary, 1996] tested by comparison of the balloon measurements during sunset with a generally accepted 3D chemical transport model, SLIMCAT, was confirmed for 20±3pptv total bromine.
|Versandkostenfrei innerhalb Deutschlands|
Wollen auch Sie Ihre Dissertation veröffentlichen?