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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 4, NUMBER 7, JULY 1991

PROFESSIONAL PUBLICATIONS...
STRATOSPHERIC OZONE

Item #d91jul9

"Sensitivity of Stratospheric Ozone to Heterogeneous Chemistry on Sulfate Aerosols," G. Pitari (Dip.to Fisica, Univ. L'Aquila, 67010 Coppito L'Aquila, Italy), G. Visconti, Geophys. Res. Lett., 18(5), 833-836, May 1991.

Using a two-dimensional model, including a comprehensive chemical code for homogeneous and heterogeneous reactions, both background and volcanic aerosols have been taken into account according to different scenarios. Increase of total Cl in the stratosphere causes a well-known O3 depletion by itself, but the effects could be highly enhanced in the presence of a large amount of volcanic aerosols.

Item #d91jul10

Special Section: "CHEOPS III: An Ozone Research Campaign in the Arctic Winter Stratosphere 1989/90," ibid., 18(4), Apr. 1991.

CHEOPS (CHEmistry of Ozone in the Polar Stratosphere) is a joint German-French research project begun in 1987 and aimed at understanding the composition of the lower Arctic stratosphere during the season when polar stratospheric clouds are most likely. The nine papers in this section report results of balloon-borne measurements (O3, NOy, HNO3, NO2, radicals, long-lived species, PSC particles), ground-based observations of various chemical species, and O3 observations by sondes and spectrophotometers.

Item #d91jul11

"Stratospheric Aerosol and Gas Experiment II and ROCOZ-A Ozone Profiles at Natal, Brazil: A Basis for Comparison with Other Satellite Instruments," R.A. Barnes (Chemal Inc., POB 44, Wallops Island VA 23337), L.R. McMaster et al., J. Geophys. Res., 96, D4, 7515-7530, Apr. 20, 1991.

Item #d91jul12

Geophys. Res. Lett., 18(4), Apr. 1991.

"Ozone Profiles at McMurdo Station, Antarctica, the Austral Spring of 1990," T. Deshler (Dept. Phys., Univ. Wyoming, Laramie WY 82071), D.J. Hofmann, 657-660. Near record levels of O3 depletion were observed; on several occasions the edge of the polar vortex was over McMurdo, when O3 above 20 km approximately doubled.

"The 1990 Antarctic Ozone Hole as Observed by TOMS," P. Newman (NASA-Goddard, Code 916, Greenbelt MD 20771), R. Stolarski et al., 661-664. Satellite instruments indicate the 1990 Antarctic ozone hole matched the 1987 record for depth, duration and area, but the ozone hole breakup was the latest yet recorded. Temperatures were below normal for late spring.

"NO2 Overnight Decay and Layer Height at Halley Bay, Antarctica," J.G. Keys (DSIR Phys. Sci., Lauder, N.Z.), B.G. Gardiner, 665-668. Calculations based on ground-based measurements suggest photolysis of only small amounts of N₂O5 inside the cold core of the polar vortex, in agreement with the previously proposed idea of N₂O5 conversion to HNO3.

"CH₄ and N₂O Photochemical Lifetimes in the Upper Stratosphere: In Situ Estimates Using SAMS Data," J.L. Stanford (Dept. Phys., Iowa State Univ., Ames IA 50011), J.R. Ziemke, 677-680. Upper stratospheric lifetimes are estimated for the first time by investigating the time dependence of tracers injected into high northern latitudes in late winter and their subsequent photochemical decay in the dynamically quiescent summer stratosphere.

Item #d91jul13

"Measuring Air from Polar Vortices," H.K. Roscoe (British Antarctic Survey, Natural Environ. Res. Council, Madingley Rd., Cambridge CB3 0ET, UK), Nature, 350(6315), 197-198, Mar. 21, 1991. Proposes a technique for using limb-sounding sensors to study ozone-destroying cells of stratospheric air shed from the Arctic winter vortex.

Item #d91jul14

J. Geophys. Res., 96(D3), Mar. 20, 1991.

"Tests of Stratospheric Models: The Reactions of Atomic Chlorine with O3 and CH₄ at Low Temperature," W.B. DeMore (Jet Propulsion Lab., Code 183-601, Pasadena CA 91109), 4995-5000. Experiments on the competitive chlorination of O3/CH₄ mixtures have been carried out at 197-217 K. Showed that the absolute rate constants recommended by the NASA Panel for Data Evaluation are accurate on a relative basis to within 15% at stratospheric temperatures.

"Ozone Loss Rates Calculated along ER-2 Flight Tracks," D.M. Murphy (ERL, NOAA, 325 Broadway, Boulder CO 80303), 5045-5053. Local ozone loss rates due to the ClO+ClO and BrO+ClO cycles are calculated using ClO, pressure and temperature from in-situ aircraft measurements and representative BrO mixing ratios, in a manner that allows one to look for patterns in the O3 loss rate that may not be apparent in separate measurements of ClO, pressure and temperature.

"Three-Dimensional Simulations of Wintertime Ozone Variability in the Lower Stratosphere," R.B. Rood (NASA-Goddard, Greenbelt MD 20771), A.R. Douglass et al., 5055-5071. Modeled O3 fields are verified against satellite and sonde measurements. By sampling the model with a limb-viewing satellite and then Kalman filtering the "observations" of the model, shows that transient subplanetary-scale features that are essential to the O3 budget are missed by the satellite system.

"The Reaction Probabilities of ClONO2 and N₂O5 on Polar Stratospheric Cloud Materials," D.R. Hanson (NOAA, R/E/AL2, 325 Broadway, Boulder CO 80303), A.R. Ravishankara, 5081-5090. Some of the reaction probabilities estimated differ from previous determinations because of the large reactant concentrations used by others; implications for polar stratospheric Cl activation are discussed.

"Satellite Ozone Comparisons: Effects of Pressure and Temperature," J.J. Olivero (Dept. Meteor., Penn. State Univ., Univ. Pk. PA 16802), R.A. Barnes, 5091-5098. Comparisons using SAGE II and SBUV data indicate that modest differences in vertical positioning can propagate into significant O3 differences in regions with strong vertical O3 gradients, particularly at 70 mbar in the tropics.

Item #d91jul15

"On the Temperature Dependence of Polar Stratospheric Clouds," G. Fiocco (Dip.to Fisica, Univ. "La Sapienza," Pl. A. Moro 2, 00184 Roma, Italy), D. Fuà et al., Geophys. Res. Lett., 18(3), 424-427, Mar. 1991. The dependence of Antarctic lidar measurements on temperature can be used to distinguish the pure nitric acid trihydrate from the mixed ice-trihydrate phase in the composition of the PSC aerosol, and to provide indication of particle sizes.

Item #d91jul16

J. Geophys. Res., 96(D2), Feb. 20, 1991.

"Stratospheric Cloud Observations during Formation of the Antarctic Ozone Hole in 1989," D.J. Hofmann (Dept. Phys., Univ. Wyoming, Laramie WY 82071), T. Deshler, 2897-2912. Describes continued measurements of PSC particle size distributions, using a new particle counter with 0.5 micron radius size resolution. A bimodal distribution was caused by small sulfate particles (0.05-0.10 micron) and by nitric acid trihydrate condensation on larger sulfate-layer particles (1.5-3.5 micron).

"Inferring the Abundances of ClO and HO2 from Spacelab 3 Atmospheric Trace Molecule Spectroscopy Observations," M. Allen (Earth Sci. Div., Jet Propulsion Lab., Pasadena CA 91109), M.L. Delitsky, 2913-2919. A simple steady-state algebraic expression for ClO, utilizing the observed ClONO2:NO2 abundance ratio, approximates the ClO results of time-dependent photochemical model calculations at sunset. A similar procedure applied to HO2 confirms for the first time the procedure suggested previously by a number of authors of deriving HOx abundances from observed fields of O3 and H2O.

"Ozone and Other Trace Gases in the Arctic and Antarctic Regions: Three Dimensional Model Simulations," C. Granier (NCAR, POB 3000, Boulder CO 80307), G. Brasseur, 2995-3011. A comprehensive chemical-dynamical model of the middle atmosphere reproduces important features noted during different observation campaigns. Despite elevated concentration of active Cl at high latitudes in the Northern Hemisphere in late winter, no ozone hole is produced by the model, a conclusion which could be modified for very stable and cold winters with delayed final warming.

Item #d91jul17

Geophys. Res. Lett., 18(2), Feb. 1991.

"Balloon-Borne Observations of Backscatter, Frost Point and Ozone in Polar Stratospheric Clouds at the South Pole," J.M. Rosen (Dept. Phys., Univ. Wyoming, Laramie WY 82071), N.T. Kjome, S.J. Oltmans, 171-174. The first measurements of this type showed a large decrease in PSC backscatter above about 14 km before the stratosphere began to warm, consistent with the loss of particles by sedimentation. No compelling evidence was found supporting earlier claims that PSC layers are anti-correlated with O3 inside the vortex.

"An Estimate of the Antarctic Ozone Modulation by the QBO," E. Mancini (Dip.to Fisica, Univ. L'Aquila, 67010 Coppito, L'Aquila, Italy), G. Visconti et al., 175-178. Comparison of simulations by a two-dimensional model with parameterization of Kelvin and Rossby-gravity wave forcing indicates a QBO-induced temperature effect and its feedback on PSC with the activation of heterogeneous chemistry.

Item #d91jul18

Geophys. Res. Lett., 18(1), Jan. 1991.

"Rate Constants for the Gas Phase Reactions of the OH Radical with CF3CF2CHCl2 (HCFC-225ca) and CF2ClCF2CHClF (HCFC-225cb)," Z. Zhang (Chem. Kinetics Div., Nat. Inst. Standards Technol., Gaithersburg MD 20899), R. Liu et al., 5-7.

"In Situ Measurements of Midlatitude ClO in Winter," S.W. Toohey (Dept. Earth Sci., Harvard Univ., Cambridge MA 02128), W.H. Brune et al., 21-24. Aircraft data collected from 38° N to 61° N show ClO enhancements that coincide with a major warming of the polar vortex to the north. While the relationship among chemical processes in the vortex and those at lower latitudes is not clear, reactions involving ClO at the concentrations observed in the midlatitudes may be responsible for the O3 decreases observed in the Northern Hemisphere.

"The Influence of Polar Heterogeneous Processes on Reactive Chlorine at Middle Latitudes: Three Dimensional Model Implications," A.R. Douglass (Atmos. Chem., Code 916, NASA-Goddard, Greenbelt MD 20771), R.B. Rood et al., 25-28. The chemistry and transport model reproduces basic features of the ClO measurements, which were made on flights from Norway to California via Virginia in Feb. 1989. This indicates that perturbed air within the polar vortex during winter is not homogeneously mixed and that the flights were made through air with the largest conversion of HCl to reactive chlorine that is seen at middle latitudes.

"Spatial and Temporal Variability of the Extent of Chemically Processed Stratospheric Air," J.A. Kaye (addr. immed. above), A.R. Douglass et al., 29-32. Simulations using a 3-D chemistry-transport model for the winters of 1979 and 1989 show that chemically processed air may be identified over much of the Arctic lower stratosphere from early January to late February, with HCl depletions being larger in 1989 than in 1979. There is some evidence for transport to midlatitudes of processed air.

"Total Ozone Measurements and Stratospheric Cloud Detection during the AASE and the TECHNOPS Arctic Balloon Campaigns," L. Lefèvre (Météo France, Ctr. Nat. Recherches Météor., 42 Ave. Coriolis, 31057 Toulouse Cedex, France), D. Cariolle, 33-36. Total O3 fields, calculated for winter 1989 using the TOVS/HIRS2 infrared radiances, generally show good agreement with TOMS O3 data. A major type II PSC event is identified in the TOVS O3 field on January 31.

Item #d91jul19

Geophys. Res. Lett., 17(12), Dec. 1990.

"Equilibrium Constant for the Reaction ClO + O2 [double arrow] ClO.O2," W.B. DeMore (Jet Propulsion Lab., 4800 Oak Grove Dr., Pasadena CA 91109), 2353-2355. Photolysis of Cl2/Cl2O/O2 mixtures at 197 K has been used to place an upper limit on the equilibrium constant for the reaction at three orders of magnitude below the current NASA recommendation.

"The Pressure Dependence of the Reaction between ClO and OClO at 226 K," A.D. Parr (Phys. Chem. Lab., S. Parks Rd., Oxford OX1 3QZ, UK), R.P. Wayne et al., 2357-2360. The importance of the reaction is discussed in the context of Antarctic ozone depletion, and an explanation for the unexpected behavior observed in earlier studies of the OClO/NO2 system is given.

Item #d91jul20

"Measurements of Arctic Total Ozone during the Polar Winter," J.B. Kerr (Atmos. Environ. Service, 4905 Dufferin St., Downsview, Ont. M3H 5T4, Can.), C.T. McElroy et al., Atmos.-Ocean, 28(4), 383-392, Dec. 1990. Ground-based measurements were made during the polar night from three Arctic stations in the winters of 1987-88 and 1988-89 with automated Brewer ozone spectrophotometers using the moon as a light source.

Item #d91jul21

"Measurement Intercomparison of the JPL and GSFC Stratospheric Ozone Lidar Systems," I.S. McDermid (NASA-Goddard, Greenbelt MD 20771), S.M. Godin et al., Appl. Optics, 29(31), 4671-4676, Nov. 1, 1990. This first reported side-by-side intercomparison of two stratospheric ozone lidar systems showed good agreement of the O3 profiles measured between 20-40 km altitude.