Tracers, stratospheric measurements

The Airborne Submillimeter SIS Radiometer (ASUR), operated on-board the German research aircraft FALCON, measures thermal emission lines of stratospheric trace gases at submillimeter wavelength. Measurement campaigns with respect to ozone depletion in the Arctic winter stratosphere were carried out in yearly intervals from 1992-97 to investigate the distributions of the radical chlorine monoxide (CIO), the reservoir species hydrochloric acid (HC1), the chemically inert tracer nitrous oxide (N20), and ozone (O3). The high sensitivity of the receiver allowed to take spatially well resolved measurements inside, at the edge, and outside of the Arctic polar vortex. This paper focuses on the results obtained for CIO from... 

It was first observed by Thiemens et al.4 that stratospheric C02 possesses a large and variable mass-independent isotopic composition. This composition was suggested as deriving from isotopic exchange with Of11)), the product of ozone photolysis.5 6 As later confirmed by rocket-borne collection of stratospheric and mesospheric air, this unique isotopic signature provides an ideal tracer of odd oxygen chemistry of the Earth s upper atmosphere, one of the most important upper atmospheric processes. There are, however, several features that require further measurement (laboratory and atmospheric) and theoretical considerations. 

Oxygen consists of three stable isotopes 0, " O and " O. For most applications only the ratio between the more abundant Lso-topes, 0 and O, is measured. If all fractionation processes in the environmental system were purely mass-dependent, measurements of 0/ 0, would be redundant, as they could be predicted from the 0/ 0 ratio. However, it has recently been ob.served that photochemical exchange between O2, Oi, and CO, in the stratosphere involves mass-independent fractionation among the oxygen isotopes (1990 Thiemens et al., 1993a, b Thiemens, 1999). Thereby O2 becomes anomalously depleted, while CO2 becomes anomalously enriched. Because of this, measurements of 0/ 0 in atmospheric O2 and/or CO2 provide an independent piece of information. Conveniently, one may define an O anomaly tracer (A 0) (Thiemens et n/., 1995b)... 

Rowland, F. S. 1976. Cosmogenic radioisotopes as stratospheric tracers, pp. 333-334 (abstract). In Measurement, Detection and Control of Environmental Pollutants. International Atomic Energy Agency. Vienna. Publ. No. STI/PUB/432. 

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