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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Annales geophysicae 12 (1994), S. 342-354 
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A three-dimensional transport model has been used to compare and contrast the extent of processing by polar stratospheric clouds during the northern hemisphere winters of 1991/1992 and 1992/1993. The model has also been used to compare the potential for ozone loss between these two winters. The TOMCAT off-line model is forced using meteorological analyses from the ECMWF. During winter 1992/1993 polar stratospheric clouds (PSCs) in the model persisted into late February/early March, which is much later than in 1991/1992. This persistence of PSCs should have resulted in much more ozone loss in the later winter. Interestingly, however, the extent of PSC processing and ozone loss was greater in January 1992 than January 1993. In January 1992 PSCs occurred at the edge of a distorted polar vortex whilst in January 1993 the PSCs were located at the centre of a much more zonally symmetrical vortex. In March 1993, distortions of the vortex led to the tearing off of vortex air and its mixing into midlatitudes.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 400 (1999), S. 551-554 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The reduction in the amount of ozone in the atmospheric column over the Arctic region, observed during the 1990s,, resembles the onset of the Antarctic ozone ‘hole’ in the mid-1980s, but the two polar regions differ significantly with respect to the relative contributions of ...
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of atmospheric chemistry 21 (1995), S. 61-79 
    ISSN: 1573-0662
    Keywords: ClO ; HCl ; ozone loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We call attention to the likely importance of the potential reaction OH+ClO→HCl+O2. It may only be a minor channel for the reaction of OH with ClO, which is often ignored in models, but if it occurs it considerably increases the rate of recovery of HCl after an air parcel has encountered a polar stratospheric cloud (PSC). The net effect of this reaction on the ozone concentration depends on the relative HCl concentration and whether the air parcel is in a PSC. When an air parcel is in a PSC and the HCl concentration is less than the sum of the HOCl and ClONO2 concentrations, heterogeneous ClO x production is rate limited by the production of HCl. Under these conditions the reaction allows HCl to be reprocessed more rapidly by the heterogeneous reactions of HCl with HOCl and ClONO2. This allows high ClO x concentration to be maintained for longer, and at a slightly higher level, than would otherwise be possible which in turn leads to more ozone depletion. When there are PSCs but HCl is in excess, or outside of the PSC regions (i.e. during the recovery phase), the reaction will always reduce the ClO/HCl ratio and hence slightly reduce the ozone loss.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-0662
    Keywords: ClO ; Fourier transform infrared
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Infrared absorption features due to ClO in the lower stratosphere have been identified from groundbased solar absorption spectra taken from Aberdeen, U.K. (57° N, 2° W) on 20 January 1995. A vertical column abundance of 3.42 (±0.47)×1015 molec cm-2 has been derived from 13 independent absorption features in the P and R branches of the (0–1) vibration-rotation band of 35ClO, spanning the spectral region 817–855 cm-1. The observed absorption features are consistent with very high levels of ClO (approximately 2.6 parts per billion by volume (ppbv)) in the altitude range 16–22 km. A comparison of this profile with a 3D chemical transport model profile indicates the observation was made inside the polar vortex and shows good qualitative agreement but the model underestimates the concentrations of ClO. Simultaneous measurements of other species were made including HCl, HF and ClONO2. These columns yield a value for HCl+ClONO2+ClO of 7.02±0.65×1015 molec cm-2. This is lower than the total inorganic chlorine (ClO y ) column of 10.7±1.6×1015 molec cm-2 estimated from mean measured (HCl+ClONO2)/HF ratios together with in-vortex HF measurements. The discrepancy is probably due to significant amounts of the ClO dimer (Cl2O2) in the lower part of the stratosphere. The measurements of highly elevated levels of ClO are used to estimate O3 loss rates at the 400, 475 and 550 K levels making assumptions about the probable distribution of ClO and Cl2O2. These are compared with loss rates derived from ozone sonde data.
    Type of Medium: Electronic Resource
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