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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 9, NUMBER 9, SEPTEMBER 1996

PROFESSIONAL PUBLICATIONS...
OZONE DEPLETION: CHEMISTRY & DYNAMICS

Item #d96sep24

Special Section: Geophys. Res. Lett., 23(17), Aug. 15, 1996. Contains 32 papers on the ATLAS (Atmospheric Laboratory for Applications and Science) space shuttle missions, with the following introduction:

"The Atlas Series of Shuttle Missions," J.A. Kaye (Office of Mission to Planet Earth, NASA, Washington DC 20546; e-mail: jkay@mtpe.hq.nasa.gov), T.L. Miller, 2285-2288. These missions, conducted in March 1992, April 1993 and November 1994, made measurements of solar (total and spectrally resolved) irradiance, atmospheric temperatures, and trace gas concentrations. The missions complemented other programs, such as NASA's Upper Atmosphere Research Satellite, which contained similar instruments and could make "correlative measurements." Topics covered in the papers include ozone in the high-latitude stratosphere, the latitudinal distribution and seasonal variation of water vapor and ClO, trace gas transport in the Arctic vortex, tracers in the vortex, trends of trace gases in the lower stratosphere, and nitrogen compounds in the stratosphere.

Item #d96sep25

"The Potential of Cirrus Clouds for Heterogeneous Chlorine Activation," S. Borrmann (Inst. Atmos. Phys., Becherweg 21, Univ. Mainz, D-55099 Mainz, Ger.; e-mail: borrmann@goofy.zdv.uni-mainz.de), S. Solomon et al., Geophys. Res. Lett., 23(16), 2133-2136, Aug. 1, 1996.

Using ER-2 data (from the Airborne Arctic Stratospheric Expeditions) taken during ascents and descents through layers of cirrus clouds, studied heterogeneous reactions of ClONO2 with H1O, of HOCl and ClONO2 with HCl, and their potential role for activation of Cl near the tropopause and the potential effects on ozone there. Found considerable potential of cirrus clouds for Cl activation. If ClONO2 and HCl are present, they are likely to be quickly converted to active Cl by cirrus clouds.

Item #d96sep26

"Balloon Observations of Organic and Inorganic Chlorine in the Stratosphere: The Role of HClO4 Production on Sulfate Aerosols," L. Jaeglé (Dept. Earth & Planetary Sci., Pierce Hall, Harvard Univ., 29 Oxford St., Cambridge MA 02138; e-mail: lyj@io.harvard.edu), Y.L. Yung et al., Geophys. Res. Lett., 23(14), 1749-1752, July 1, 1996.

Between 15 to 20 km, the sum of measured HCl, ClONO2 and HOCl could not account for all the inorganic Cl. The new species measured, HClO4, could bring to closure this budget deficiency. This also confirms laboratory measurements that the reaction of ClO radicals on H1SO4 produces small amounts of perchloric acid.

Item #d96sep27

"Chemical Loss of Polar Vortex Ozone Inferred from UARS MLS Measurements of ClO During the Arctic and Antarctic Late Winters of 1993," I.A. MacKenzie (Dept. Meteor., Univ. Edinburgh, Edinburgh, EH9 3JZ Scotland), R.S. Harwood et al., J. Geophys. Res., 101(D9), 14,505-14,518, June 20, 1996.

Used a computationally cheap, and easily initialized photochemical model with UARS MLS measurements of ClO to calculate ozone destruction rates within polar vortices due to ClO + ClO, ClO + BrO, and ClO + O catalytic cycles. Test integrations gave good agreement with more detailed model calculations. The estimated chemical destruction on isentropic surfaces in the lower stratosphere is broadly similar to the observed change in ozone distribution, implying that the change is dominated by chemical destruction.

Item #d96sep28

Two related items in Science, 272(5268), June 14, 1996:

"Polar Clouds and Sulfate Aerosols," M.A. Tolbert (Dept. Chem., Univ. Colorado, Boulder CO 80309; e-mail: tolbert@colorado.edu), 1597. Discusses how the theoretical work of the following article helps explain why type I PSCs form over and over throughout the winter, and what questions remain.

"Melting of H1SO4¨4H1O Particles upon Cooling: Implications for Polar Stratospheric Clouds [PSC]," T. Koop (M. Planck Inst. Chem., POB 3060, D-55020 Mainz, Ger.), K.S. Carslaw, 1638-1641. Solid PSC can form on sulfuric acid tetrahydrate (SAT) nuclei, but laboratory experiments have shown that PSC nucleation on SAT is strongly hindered. Proposes a PSC formation mechanism in which SAT particles melt upon cooling in the presence of HNO3 to form liquid HNO3-H1SO4-H1O droplets, 2-3 K above the ice frost point. This offers a PSC formation temperature that is defined by the ambient conditions and sets a temperature limit below which PSCs should form.

Item #d96sep29

"Is It Possible to 'Repair' the Ozone Holes?" I.L. Karol' (Voyeykov Main Observatory, Russia), A.A. Kiselev, V.A. Frol'kis, Atmos. & Oceanic Phys., 31(1), 113-115, June 1995. English Edition.

Used a radiative-photochemical model to estimate the intensity and optimum altitude needed for an ozone source to increase total column ozone under conditions of the Arctic and Antarctic ozone holes. The ozone source considered is not related to any particular project nor does it depend on any particular method of generation. The calculated required injection is so large as to be unrealistic at the current level of technical development.

Item #d96sep30

"Numerical Simulation of the Dynamical Response of the Arctic Vortex to Aerosol-Associated Chemical Perturbations in the Lower Stratosphere," X. Zhao (Dept. Atmos. Sci., Univ. California, Los Angeles CA 90095), R.P. Turco et al., Geophys. Res. Lett., 23(12), 1525-1528, June 1, 1996.

Used a general circulation model coupled to a stratospheric photochemistry model to study the effect on the Arctic polar vortex of ozone depletion catalyzed by volcanic aerosols. Model results show that temperatures may be depressed as much as 3-7 K in late March in the lower stratosphere at northern middle and high latitudes, owing to ozone-radiation-dynamics feedback. The simulations demonstrate the close coupling between the dynamics and chemistry in this region, and the complexity of analyzing cause and effect

Item #d96sep31

"Model Study of Polar Stratospheric Clouds [PSCs] and Their Effect on Stratospheric Ozone. 2. Model Results," X. Tie (NCAR, POB 3000, Boulder CO 80307), G.P. Brasseur et al., J. Geophys. Res., 101(D7), 12,575-12,584, May 20, 1996.

Used the model described in Part 1 to study the effect of heterogeneous reactions on PSC surfaces on stratospheric ozone. Calculations show that these reactions are the likely cause of the ozone decrease from 1980 to 1990 in the Antarctic and the Arctic. Also demonstrates that the future density of Arctic PSCs could be enhanced by the potential emission of water vapor and nitrogen species by high altitude aircraft, which could in turn lead to a maximum of ozone depletion of 10% at northern high latitudes in winter.

Item #d96sep32

"Decline in the Tropospheric Abundance of Halogen from Halocarbons: Implications for Stratospheric Ozone Depletion," S.A. Montzka (CMDL, NOAA 325 Broadway, Boulder CO 80303), J.H. Butler et al., Science, 272(5266), 1318-1322, May 31, 1996.

Previous studies have shown that tropospheric chlorine attributable to anthropogenic halocarbons peaked near the beginning of 1994 and has started to decrease. The authors have estimated the effect of this trend on stratospheric ozone, concluding that the amount of reactive chlorine and bromine there will reach a maximum between 1997 and 1999. Concentrations will decline thereafter if limits outlined in the adjusted and amended Montreal Protocol are not exceeded in future years.

Item #d96sep33

Special Issue: J. Geophys. Res., J.C. Gille, S.T. Massie, W.G. Mankin, Eds., 101(D6), April 30, 1996.

Contains 46 papers that evaluate the quality of the data collected between 15 and 100 km altitude by the Upper Atmosphere Research Satellite (UARS). The success of UARS data validation rests on several foundations. There was enthusiastic support and involvement of the instrument principal investigators in planning and evaluation. Early planning, budgeting and staffing for correlative measurements were essential. Time and effort were taken to refine and improve algorithms, to acquire correlative measurements and supply them to investigators.

Item #d96sep34

"The Role of Aerosol Variations in Anthropogenic Ozone Depletion at Northern Midlatitudes," S. Solomon (Aeronomy Lab., NOAA, 325 Broadway, Boulder CO 80303), R.W. Portmann et al., J. Geophys. Res., 101(D3), 6713-6727, Mar. 20, 1996.

Quantifies the role of volcanic stratospheric aerosols in ozone depletion by using satellite measurements of aerosol extent as input to a two-dimensional dynamical-chemical model. The model simulated the effects of heterogeneous ozone chemistry at northern midlatitudes over the last 15 years, a time period that included major volcanic eruptions. Results show that interannual and decadal changes in aerosols likely played a substantial role, along with trends in anthropogenic Cl and Br, in triggering the observed ozone losses. The timing and magnitude of future ozone losses in the area of investigation are likely to be strongly dependent on volcanic aerosol variations, as well as on future Cl and Br loading. The results also underscore the potential importance of any future source of particles, such as supersonic aircraft emissions.

Item #d96sep35

"ClONO2 Total Vertical Column Abundances Above the Jungfraujoch Station, 1986-1994: Long-Term Trend and Winter-Spring Enhancements," C.P. Rinsland (Atmos. Sci. Div., NASA-Langley Res. Ctr., Hampton VA 23681), R. Zander et al., ibid., 101(D2), 3891-3899, Feb. 20, 1996.

Solar absorption spectra show a regular, long-term increase in ClONO2, and in general reflect a linear rate of increase and 1Õ uncertainty equal to 4.0% ± 0.7% per year referenced to 1990.