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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 3, NUMBER 9, SEPTEMBER 1990

PROFESSIONAL PUBLICATIONS...
STRATOSPHERIC MODELING

Item #d90sep50

"Global Impact of the Antarctic Ozone Hole: Dynamical Dilution with a Three-Dimensional Chemical Transport Model," M. Prather (NASA/GISS, 2880 Broadway, New York NY 10025), M.M. Garcia et al., J. Geophys. Res., 95(D4), 3449-3471, Mar. 20, 1990.

Examined different linearizations of ozone chemistry in the ozone hole and showed that the calculated column ozone is sensitive to the chemical time constants in the lower stratosphere. A budget analysis for the southern high-latitude stratosphere indicated that the ozone hole is replenished equally by photochemical regeneration and by reduced transport of ozone into the troposphere, with a lesser fraction being filled in by an increased flux from the tropical stratosphere.

Item #d90sep51

"Global Impact of the Antarctic Ozone Hole: Chemical Propagation," M. Prather (address immed. above), A.H. Jaffe, ibid., 3473-3492.

Incorporates photochemistry, molecular diffusion, and the stretching of air parcels by wind shear in a one-dimensional model to examine the chemical mixing of strato-spheric air over spatial scales from tens of kilometers to meters. Four cases were examined, with varying degrees of chemical and physical processes included. Chemical propagation of the Antarctic ozone hole occurs in two phases: rapid loss of ozone in the heterogeneously processed parcels as they evolve in isolation, and a slower relative recovery of ozone over the following months.

Item #d90sep52

"An Interactive Chemical Dynamical Radiative Two-Dimensional Model of the Middle Atmosphere," G. Brasseur (NCAR, POB 3000, Boulder CO 80307), M.H. Hitchman et al., J. Geophys. Res., 95(D5), 5639-5655, Apr. 20, 1990.

The distributions of chemically active species belonging to the oxygen, hydrogen, nitrogen and chlorine families are calculated for present-day conditions. By applying near the tropopause a different dynamical forcing in each hemisphere, the model produces hemispheric asymmetries in dynamical quantities and trace gas densities in good agreement with climatological values. Shows that with many feedback mechanisms included in its formulation the model is well adapted to study the effects of human or natural perturbations.

Item #d90sep53

"Response of an Interactive Two-Dimensional Model to Ozone Changes: An Estimate of the Radiative Dynamic Feedback Effect," H.R. Schneider (AER Inc., 840 Memorial Dr., Cambridge MA 02139), M.K.W. Ko, ibid., 5657-5668.

Analyzes a two-dimensional model using a simplified ozone chemistry model and stationary linear models for the diabatic circulation. Results show an increase in the predicted high-latitude ozone depletion with decreasing eddy diffusion in the model stratosphere. This effect can be explained by the reduction (with decreasing eddy diffusion) of advective and diffusive horizontal transport from the tropics to the polar region in the lower stratosphere.

Item #d90sep54

"A General Circulation Model Simulation of the Springtime Antarctic Ozone Decrease and Its Impact on Mid-Latitudes," D. Cariolle (Dir. Meteor. Nat., Ctr. Nat. Recherches Meteor., 42 Ave. Coriolis, 31507 Toulouse, France), A. Lasserre-Bigorry, J.-F. Royer, J. Geophys. Res., 95(D2), 1883-1898, Feb. 20, 1990.

Results of this comprehensive simulation show very good agreement with the ozone measurements made during spring 1987: ozone decrease from August to mid-October, followed by the development of a high-latitude anomalous circulation with a warming of the upper stratosphere resulting from dynamical heating. A significant residual ozone decrease is found at the end of the model integration (seven months after the final warming and the vortex breakdown), suggesting ozone trends predicted by photochemical models which do not take into account the high latitude perturbed chemistry are clearly inadequate.

Item #d90sep55

"El Chichon Volcanic Aerosols: Impact of Radiative, Thermal, and Chemical Perturbations," D.V. Michelangeli (Div. Geol. Planetary Sci., Calif. Inst. Technol., Pasadena CA 91125), M. Allen, Y.L. Yung, ibid., 94(D15), 18,429-18,443, Dec. 20, 1989.

Examines the consequences of the eruption of the El Chichon volcano on the Earth's stratospheric chemistry, a known change, to be able to evaluate the completeness of a photochemical model to represent changes in the atmosphere. Combined radiation and thermal perturbations on O, OH, HO2, H2O2, NO, NO2, NO3, N₂O5, HNO3, HO2NO2, Cl, ClO, ClO2, HOCl, ClNO3 and HCl were calculated and presented. The effects of a number of heterogeneous reactions, some believed to be important for the Antarctic stratosphere, were assessed with the model.

Item #d90sep56

"Evaluation of Excess Carbon 14 and Strontium 90 Data for Suitability to Test Two-Dimensional Stratospheric Models," H. Johnston (Dept. Chem., Univ. Calif., Berkeley CA 94720), ibid., 18,485-18,493.

Reviews data from Atomic Energy Commission reports concerning the atmospheric distribution of radionucleides following the nuclear bomb tests of 1958-1959 and 1961-1962 and looks at C14 and Sr90 as possible inert tracers to test two-dimensional stratospheric-tropospheric models. Contrary to some views, the author shows that the C14 data are suitable to test some aspects of altitude, transport, horizontal and vertical transport, and the long-term one-dimensional aspect of a two-dimensional model over the period 1966-1970, for certain geographic areas. Sr90 might be used as a model for the distribution and gross settling rate of the natural stratospheric aerosol layer between 15 and 25 km.

Item #d90sep57

"Sensitivity Study of Advection and Diffusion Coefficients in a Two-Dimensional Stratospheric Model Using Excess Carbon 14 Data," R.-L. Shia (Div. Geol. Planetary Sci., Calif. Inst. Technol., Pasadena CA 91125), Y.L. Yung et al., ibid., 18,467-18,484.

Using the California Institute of Technology/Jet Propulsion Laboratory two-dimensional transport model, the time evolution of excess C14 in the stratosphere and the troposphere from October 1963 to December 1966 was studied. The model provides a satisfactory simulation of the observed data. Excess C14 was removed from the atmosphere with surface deposition velocities nuS=3 x 10-3 cm s-1 and nuN=5 x 10-3 cm s-1 in the Southern and Northern Hemispheres, respectively. This result is contrary to the understanding that oceans are a dominant sink for excess C14.

Item #d90sep58

"2-D Model Simulations of Anomalous Spring Variations of Ozone, Temperature and Other Minor Trace Constituents in the Southern Polar Region," R.K.R. Vupputuri (Canadian Clim. Ctr., Atmos. Environ. Serv., Downsview, Ont. M3H 5T4, Can.), Atmos.-Ocean, 27(4), 728-738, Dec. 1989.

The normal transport coefficients and the standard chemistry have been altered to represent the anomalous dynamical and chemical conditions in the extremely cold lower stratosphere of Southern Hemisphere spring. Results show that both dynamical and chemical mechanisms must be used to explain the observed rapid spring decline of total ozone in this region.