HR: 1340h
AN: A43A-0870    [Abstracts]
TI: The Ozone Hole -- a Mystery Reborn?
AU: * von Hobe, M
EM: m.von.hobe@fz-juelich.de
AF: Inst. of Chemistry and Dynamics of the Geosphere ICG-1: Stratosphere, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
AU: Grooß, J
EM: j.-u.grooss@fz-juelich.de
AF: Inst. of Chemistry and Dynamics of the Geosphere ICG-1: Stratosphere, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
AU: Müller, R
EM: ro.mueller@fz-juelich.de
AF: Inst. of Chemistry and Dynamics of the Geosphere ICG-1: Stratosphere, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
AU: Stroh, F
EM: f.stroh@fz-juelich.de
AF: Inst. of Chemistry and Dynamics of the Geosphere ICG-1: Stratosphere, Forschungszentrum Jülich GmbH, Jülich, 52425, Germany
AB: In 1985, Farman et al. discovered the near complete disappearance of the stratospheric ozone layer over Antarctica in spring. This 'Ozone Hole' took the atmospheric research community by surprise as it could not be explained by the known catalytic cycles removing ozone in the stratosphere. McElroy et al. (1986) and Molina and Molina (1987) seemed to have solved the enigma by proposing two new catalytic cycles -- the ClO-BrO-cycle and the ClO dimer cycle -- that could rapidly destroy ozone at cold temperatures and high zenith angles. Subsequent work describing the kinetics of these cycles as well as stratospheric observations of chlorine and bromine compounds supported their theory and led to atmospheric chemistry models reproducing observed ozone loss reasonably well. Today, more than 20 years after the discovery of the ozone hole and the ratification of the Montreal Protocol, a new laboratory study (Pope et al., 2007) -- suggesting much smaller absorption cross sections and hence photolysis rates of the ClO dimer -- seriously calls into question our understanding of how ozone is destroyed in the spring polar stratosphere. With the new cross sections, both the dimer cycle and the ClO-BrO-cycle run much slower, and observations of neither chlorine compounds nor ozone loss are reproduced by model simulations (von Hobe et al., 2007): the known catalytic cycles cannot cause an ozone hole. Obviously, this also calls into question our ability to predict future polar ozone depletion. In search for an explanation, we discuss possible shortcomings of the Pope et al. experiment that could lead to an underestimation of the dimer absorption and examine various new chemical processes for their likelihood to influence chlorine partitioning and cause significant ozone loss in the atmosphere and at the same time go undetected in laboratory based kinetic studies. A strategy is presented for designing the tests needed to unambiguously confirm or rule out proposed solutions to the dilemma. Farman, J.C. et al., Nature 315, 207, 1985.
McElroy, M.B. et al., Nature 321, 759, 1986.
Molina, L.T. and Molina, M.J., J. Phys. Chem. 91, 433, 1987.
Pope, F.D.et al., J. Phys. Chem. A 111, 4322, 2007.
von Hobe, M. et al., Atmos. Chem. Phys. 7, 3055, 2007.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0340 Middle atmosphere: composition and chemistry
DE: 1704 Atmospheric sciences
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting