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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 1, NUMBER 2, AUGUST 1988

PROFESSIONAL PUBLICATIONS...
ATMOSPHERIC CHEMISTRY

Item #d88aug31

"Measurements of Several Atmospheric Gases Above the South Pole in December 1986 from High-Resolution 3 to 4 micro m Solar Spectra," A. Goldman (Dept. Phys., Univ. Denver, Denver CO 80208), F.J. Murcray et al., J. Geophys. Res., 93(D6), 7069-7074, June 20, 1988.

The technique of spectral least squares fitting was used to analyze a 0.02 cm-1 resolution 3 to 4 micro m solar spectrum resulting in information on the total column amounts of several atmospheric gases. Identification of 12CH3D absorption features and a search for H2CO absorption in the spectral data are also described.

Item #d88aug32

"Stratospheric Nitrogen Dioxide Concentrations as Determined From Limb Brightness Measurements Made on June 17, 1983," C.T. McElroy (Atmos. Environ. Svc., ARPX, 4905 Dufferin St., Downsview, Ont. M3H 5T4, Can.), ibid., 7075-7083.

A multiwavelength spectrometer with limb scanning optics was developed to make NO2 measurements in the stratosphere. Observations were made at an altitude of 33 km at 32° N, 98° W for a period of several hours. The mixing ratio of NO2 was observed to be (3.5 + or - 0.8) ppbv at 28 km, in reasonable agreement with solar occultation measurements. The time rate of change of the NO2 concentration at 28 km is estimated at (0.18 + or - 0.06) ppbv per hour at 2200 coordinated universal time.

Item #d88aug33

"Temperature Dependence of the Atmospheric Photolysis Rate Coefficient for NO2," R.E. Shetter (NCAR, POB 3000, Boulder CO 80307), J.A. Davidson et al., ibid., 7113-7118.

Theoretical estimates of the temperature dependence (expressed as j1 ratios) based upon recently reported cross section and quantum yield data are more consistent with these experimental measurements than those based upon the currently accepted values.

Item #d88aug34

"The Stability and Photochemistry of Dimers of the ClO Radical and Implications for Antarctic Ozone Depletion," R.A. Cox (Eng. Sci. Div., Harwell Lab., Didcot, Oxon 0X11 0RA, UK), G.D. Hayman, Nature, 332(6167), 796-800, Apr. 28, 1988.

Measurements of the ultraviolet spectrum of the Cl2O2 molecule formed at temperatures in the range 203-300° K by recombination of ClO radicals are reported. The equilibrium constant for the reaction has been determined and the products of photolysis of Cl2O2 at 254 nm investigated. The main photodissociation pathway for Cl2O2 probably produces Cl atoms and chlorine peroxy radicals, as assumed in calculation of the ozone loss by the ClO and Cl2O2 catalytic cycle in the Antarctic stratosphere.

Item #d88aug35

"Causes of Ozone Depletion," B. Thrush, ibid., 784.

Several sequences of chemical reactions that regenerate chlorine atoms have now been invoked to explain the rapid decay during spring of ozone trapped in the Antarctic polar vortex. This involves the dimerization of ClO radicals at very low temperatures to form Cl2O2, which is then broken down by ultraviolet light, regenerating chlorine atoms which destroy ozone.