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Appendix C RECENT DEVELOPMENTS IN STRATOSPHERIC PHOTOCHEMISTRY Steven C. Wofsy and Jennifer A. Logan Division of Applied Sciences Harvard University INTRODUCTION Studies of the stratospheric ozone layer are impeded by two characteristics common to many environmental ques- tions. First, it is impossible to perform meaningful, controlled experiments to test the response of the system to changes in environmental parameters. Second, the chemistry of the system is very complex, involving labile species at low concentrations subject to transport processes that are not well understood. These difficulties force us to rely on simulations using theoretical models to assess possible perturbations to stratospheric ozone. The models are inevitably too simple to describe the complete physical system and yet are often so complicated that it may be quite difficult to understand the models and to draw model-independent conclusions from the results. This paper examines recent models of stratospheric ozone and associated chemical species, with emphasis on developments subsequent to the earlier NRC study on the stratosphere (NRC 1979). The discussion relies primarily on calculations performed using our own one-dimensional model of the stratosphere (Logan et al. 1978, Wofsy 1978) and on results from two recent two-dimensional models (Miller et al. 1981; Steed et al. 1982; Ko, Sze, and co-workers reported in Hudson et al. 1982). This choice reflects our access to model results and our view that these models contain most of the essential features of other operational models. 167

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168 EFFECTS OF NEW KINETIC DATA ON MODEL RESULTS Species Concentrations Stratospheric models in use during the previous NRC study (NRC 1979) appeared to underestimate by a factor of between 2 and 5 concentrations of NO and NO2 below 25 km, and to overestimate the concentration of C10 by a factor exceeding 10 at the same altitudes. These discrepancies may be attributed to inaccurate values for kinetic data affecting calculation of the concentration of the OH radical. Below 25 km, NO and NO2 are controlled by chemical exchange with HNO3, the major odd-nitrogen species, with the main reactions being NO2 + OH + M ~ HNO3 + M HNO3 + he ~ NO2 + OH NO2 + he ~ NO + O NO + O3 ~ NO2 + O2 Nitrogen dioxide and nitric oxide concentrations thus vary inversely as the concentration of OH, (1) (2) (3) (4) [NO2] ~ J2[HNO3] (5a) kl[M] [OH] [NO] ~ J2[HNO3] J3 1 (5b) kl[M] k4[O3] [OH] where [x] denotes the concentration of species x and ki(Ji) refers to the rate coefficient (photolysis rate) for the ith chemical reaction. The concentration of C10 also is controlled by inter- change with a more abundant species, HC1, but in this case C10 increases with OH. The principal reactions are HC1 + OH ~ H2O + C1(6) C1 + O3 + C10 + O2 C1 + CH4, H2, H2CO ~ HC1 + CH3, H. HC(8-10) C10 + NO ~ C1 + NO2,(11 ) which lead to the expression

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169 C10 ~ ~ [OH]2 k6[HCl] [OH]k7[O3] {k8 [CH4]+kg [H2] +klo [H2CO]}kll[NO] k6[HCl]k4k7[O3] kl[M] {k8 [CH4] +kg [H2]+klo [H2CO]}kllJ3J2 [HNO3] (12a) (12b) Hence [C10] increases as [OH] 2. McConnell and Evans (1978) pointed out that model and observations could be brought into agreement if it was assumed that the model overestimated the concentrations of OH, and they noted that such an error could strongly affect estimates quoted in NRC (1979) for the response of ozone to enhanced levels of stratospheric chlorine or odd nitrogen. New laboratory measurements lend support to the hypothesis advanced by McConnell and Evans (1978) and others (Turco et al. 1981). Wine et al. (1981) and Nelson et al. (1981) showed that the rate for the reaction OH + HNO3 ~ H2O + NO3 (13) increases at low temperature. This reaction is the major sink for odd hydrogen below 25 km, as shown in Figure C.1. Rates for reactions involving peroxynitric acid (HOONO2 or HNO4) have also been revised recently as shown in Table C.1. Rates for formation of HNO4 and for reaction between OH and HNO4 appear to be faster than formerly believed, HO2 + NO2 + M ~ HNO4 + M HNO4 + OH ~ H2O + products (14) (IS) (NASA 1981, Littlejohn and Johnston 1980, see also Hudson et al. 1982), whereas photolysis of HNO4 may be slower than indicated by earlier studies, HNO4 + hv ~ products (Molina and Molina 1981). These results, further work, indicate that reaction (15) pathway for loss of odd hydrogen ~ (16) if confirmed by is a ma~or (see F~gure C.1). Figure C.2 shows how calculated profiles for OH, HO2, C10, NO, and NO2 (at noon) have changed in response to the new laboratory rate data. Model concentrations of OH have been lowered by about a factor of 3 at 20 km, NO and NO2 have been increased by a

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170 50 . 45 40 E - 35 a 1 1 1 1 1 1 1 1 1- 1 -W-I 1 1 1 1 ~1 W- ~1 1 1 1 1 11 ' ~ \ OH + HNO3 V- OH + H202 HO2+0H \ -it\ \ 30 25 20 15 - \ me,, i,: OH + HNO4 / \ / ~ / O H + H NO4 /~/ I ~t l l l ,/ /~OH+HNO3 .. 1. 1 l,__ I I_I I I I I LL L_ . 2 103 104 RATE ( cm~3 sect ) FIGURE C.1 Rates for loss of odd hydrogen, averaged over a 24-hour period. Profiles are shown for 30N latitude at equinox. Results are from the Harvard one-dimensional model (Logan et al. 1978) using kinetic data from Hudson et al. (1982~.

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171 Ct Q.) 00 Ct ~ ~ _ ._ ~ Ct _ a~ ~ C~ _ o ._ C~ o _. C) C~ e~ C~ o Ct o ._ C~ Ct C: m V' l C) C~ - c) ~o o C) Ct C~ 4 - _~ o ~ _ _ oo _ Z o o%\ ~ - _ _' . . . ~ oo o C~ ~ X X X X X _ 1 1 ~o ~o _ ~ _ C~ C~ X ~ X o . o . o' s:L X _ _ 1 1 o o _ _ C~ o - ~_ x - 1 o _ C~ X X ~ X ~ . o _ oo _ _ 1 1 o o _ _ - o _, x - 1 o o _ _ XX XX ~ oo o . .. . oo ~ ~ ~t _ C o ~ + O ~ ~ O ~ Z + O ~ ~0 Z O ~0 ~ X + + Ze'+ + :r 5: 0 := ~ O O ~ O O ~_ - 00 . _ ~ C~ _ _ 0 . _ ~ Ct C~ ~ == ~o C~ ~Q

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172 55 50 45 - ~ 40 5 Hi: 30 25 _ 20 1 , 1~,,l/ 1 1/1 , lo6 a 107 55 50 45 40 535 30 25 20 ... . 1_ ~ .~_~11 I i ~__,_, 1 ,, ~1-~1 I,,, 105 1o6 10 ~ CtO (cm~3) C 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 11 81~\\ I r--r- I l-r-~-~---r--~ I I i l: 80 \ 81479 lo8 lo6 ) . // 1 ~ 111111 1 10' b 1 1 ~1 1 1 - 1- - - 1 1 1 1 -rams ~- ~I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1o6 ~\,,,1979 1981 Slow CIO+N,~ ~ ~1980 fit/ 8 109 FIGURE C.2 Altitude profiles for (a) HO2, (b) OH, (c) C1O, (d) NO and NO2 at noon. The labels 1979, 1980, and 1981 indicate rate constant sets shown in Table C.1 (Hudson and Reed 1979, NASA 1981, and Hudson et al. 1982, respectively). lo8

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173 ' ' ''''4 '' ' ' '''''I ' 1 40 30 20 40 Y 30 LLJ C) ~ 20 NO2 _ , _ - - 1 1 - d 10 107 .~ 'it ) 1979,~' / 1981 1 1 1 1 1~x NO 1 !\ ,- I lo8 NUMBER DENSITY (cm) FIGURE C.2 (Continued) 109

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174 . . . similar factor, and calculated C1O concentrations have decreased by nearly a factor of 10. It may seem surprising that relatively modest changes in the rates for (13) through (16) should have such dramatic effects on calculated profiles for OH. Chemical interchange among BOX radicals is quite rapid in the lower stratosphere, with lifetimes for HO2 and OH at noon about 50 and 10 s, respectively. The fast reactions establish the ratio of [OH] to [HO2], but radical production and loss reactions control the absolute concentrations. Recombination reactions for HOX radicals are inefficient in the lower stratosphere, such that the chemical lifetime for the sum of HO2, H. and OH exceeds 500 s (see Figures C.1 and C.2). Hence slow processes such as (13) and (15) can exert a major influence on the composition of the stratosphere. Slow recombination reactions are difficult to study in the laboratory, especially for stratospheric temperatures and pressures, and the future may well hold further chemical surprises in this area. The present set of reaction rate data brings calcula- tions and observations into reasonably close agreement below 30 km, as shown in Figures C.3, C.4, and C.5 for OH, HNO3, NO2, NO, O. and C1O. The figures also illustrate the relatively poor agreement obtained by using the 1979 rate data. Unfortunately, the comparison is not yet definitive. Data on OH and O are nonexistent below 30 km, and few simultaneous observations are avail- able for NO, NO2, and HNO3. The vertical gradient for NO does not coincide very well with observations by Ridley and co-workers (Ridley and Schiff 1981, Ridley and Hastie 1981) (Figure C.3d) but does agree with data obtained by Horvath and Mason (1978) (see also Hudson et al. 1982) (Figure C.3c). The model predicts more HNO3 than is observed between 25 and 30 km. The apparent discrepancy observed for O (Figure C.3f) at low altitude may be attributed to differences for [O3] and local albedo between the model and the particular observations. The model does predict accurate values of the ratio [O]/[O3], as shown in Figure C.3g. Observations of C1O require special consideration. Reported measurements are shown in Figure C.4 (Weinstock et al. 1981, Anderson et al. 1980). Summer data (solar declination of >0) fall in a rather narrow band, as predicted by the model, except for anomalous results obtained on June 15, 1979, and July 14, 1977. (The anomalous Bastille Day profile (July 14, 1977, Anderson

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175 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 70: LLJ 60 _ ~ _ SO-SO _ 4Sr _ - a ~_ 40 1 , 1 , 1 1 1 1 1 J 1 1 1 1 1 6 10t OH CONCENTRATION (cm~3) 1 1 1 1 1 1 1 1 BAllOON-BORNE IN SITU 12 Jan 1976 ( x2) x 80 ~40-~ 26 Apr 1977(x2)x.80 i Y 14 JuI 1977,x 41 35 :~:~ 107 OH CONCENTRATION (cm~3) I i lo8 1 I ~ 30 lo6 1 111 lo8 FIGURE C.3 Model results for OH in the (a) upper and (b) middle stratosphere; (c) HNO3; (d) NO2; NO in the (e) lower and (I) upper stratosphere; (g) 0(3P); and O [O] / [O3 ] compared with measurements. The measurements are presented and discussed in Hudson et al. (1982). Calculations are appropriate for 30N latitude at equinox and for solar zenith angles and local times as indicated.

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176 45 35 30 25: ! 50 45 40 1 1 1 1 1 1 1 11 1 ,1 1 1 1 1 111 1 1 1 1 1 i 1i fischer (1980) HNO _ 0 May 1979 - 31 N 3 O Feb 19?9-31N \ :cicu/oted MlOlATITUDES Arno~d eto~ (1980) 0 ~ ,' NORTH _* Nov 1977-45N * \ Evans et al (1978) ~\ Jul-Aug 74-76 51N ~0 v)\ _ Harries et al. (1976) 5 ~ 0\ 0 Sept 1974-45N 3Vo \ Fontanellc etal (1975) O- ~ \O| Ju~ 1973-48N 0310- Murcray et c~. (1980) ~ ~i j v Oct 1979-32N O=/~| 20- L zrus and Gandrua(1974) ~ 8 r~nc 1971 0 0 ~ii ~ 0 0 SPring 1971 I O SPring 1972 0 c 15r 0 SPring 1973 ~32N 101 1 1 1 1 1 1 1 ! 1 1 1 1 1 11611 1 1 1 1 1 1 1 1 1 1 ! ! ! ! ! ! 0.1 1 10 MlXiNG RATIO (ppbv) VERTICAl COlUMN I 11 to40km (86 ~ 4.0)x1o15cm~ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 SUNSET 32-33N - MURCRAY ~ COWORKERS x 7 DEC 1967 IR Absorption - Murcray et al (1974) '& 9 fEB 1977 Visible Absorption ~Goldman et al (1978) - 35 a 10 OCT 1979 IR Absorption Blatherwick et al ( 1980) 30- flSCHER ~ COWORKERS (1980) ~: 1 25 20 O 9 fEB 79 ~ Visi ble Absorption -~ 5 MAY 79' - NO? 15 1 1 1 1 1 llll 1 , 71 86 94 ~/ o ~/ ~ / d 1 11 1 111 1 1 1 11 1111 1 1 1 1 1 1 11 0.1 1 10 M IXI NG RATIO ( ppbv) FIGURE C.3 (Continued)

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177 451 1 1 1 1 1 iIII 1 1 1 1 tIIiI 1 1 1 1 1 IiII 1 i i RII)I fY ~ COWORKERS 25 l 15- ... . 40-~ 25 OCT 1977 32N S5-75 e 12 DEC 1977 34S 75-533 35 _ ~ 14 DEC 1977 34S 75-53 v 30 OCT 1978 32N 53-69 I o 8 NOV 1978 32N 55-75 ~, 301 ~12 AUG 1978 51N 54-57 ~I 251 5 1 ~ 20' oO' - v ;~- ~ N O 4~ ..' 1 1 1 1 1 1 1 1 1 1 1 ! 1 1 1 1 1 1 1 1 1 1 101 1 1 1 1 1 1111 ~ 0.1 1 10 MIXING RATIO (ppbv) 1 e 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 60 55 45 40 35 30 25 HORVATH ~ MASON x - 8 APR 1975 39N 41 o 19 MAR 1976 39N 49 _ 0 14 JUl 1980 39N 16 16 OCT 1980 39N 61 NO oo o \~X-71 o o \ o~ o od o o~^ 0 o~,o aO o) o o ,`70 / ~/ o i~1 ~ ~ ~ ~ ~ ~ ~1 ~ ~ ~ ~ ~1 ~ ~ ~ ~ l, f 0.1 1 10 MIXING RATIO (ppbv) FIGURE C.3 (Continued)

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195 \ 40 30 - - Cl 20 -\ , _ . 10 Oo 0.5 CH4 MIXING RATIO ( ppm) a Ehhalt 44; 48N 28/6/79 X15/11/77 16/6/79 +15/12/77 21/12/77 \30N \\ \~ ~ 45: .; .~1 \~\ \ Bush et al 41N 2/14/78 0 5/11/18 Farmer et al 2/76 32N ~1 Shhalt et al. 44N - 6/7/77 6/16/77 9/9/77 9/26/77 \ ~ W, ~- No N5* ~ Wo _ to j of taco 1 x 1.0 1.5 FIGURE C.11 Model results for (a) CH4, (b) N2 O. (c) CF2 C12, (d) CFC13, (e) CH3 C1, and (f) C2 H6 compared with observations. The measurements are discussed in Hudson et al. (1982), and model profiles are from the Harvard one-dimensional model with mixing surfaces, unless otherwise indicated.

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196 40 35 30 Y 2 lo c 401 35 30 25 . LIJ => 20 ,~,~ 0 0 1 1 1 1 1 1 1 1 1 1 'I 1 1 1 1 1 ~o~ - ^Oo~.. - 1 year chemica I lifetime 1000 ~ . .! ~1 ~ o NOAA 41 N KFA 44N_ NOAA 5N ~.1 . . . . . . . . ~11 lo-lo CF2 Ct2 (mole fraction) FIGllRE C.11 (Continued) lyre Tc it 9

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197 40 35 30 25 20 15 10 d _ 10 -12 40 30 r 11~ 25 -- 20 ct 35 15 10 0 0 o 5 lo-12 --r ~ I t- I I I I I ~l I ~ /\ 0 \ ~ 6/78 44N 6/28/79 0 6/16/79 1 1 1 1 1 1 1 10-11 \45N\30N V ~ ^\ \ o o \ _ ~ I ~ I I I I ~ ~ I I I I I d~ \ lo-lo CFCt3 MOLE FRACTION \ \~\ ~lyr 10-9 1 1 1 1 1 1 1 1 0 NOAA 41 5 ~ K FA 44 ARC, 5 0 W~ o~o !,o I i I I I I I I I I l I ! I I I I I l l I l l I l I ~11 lo-lo CH3C~ MOLE FRACTION FIGURE C.11 (Continued) lmo. 3 most lyr. (30N) lyr. (0N) chemicol lifetime 109

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198 35 30 _ 25 - lJJ 20 =) ~ 15 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ~ ~ 1 1 1 1 1 1 1 1 1 . 10 is f - . - - O 1 1_ 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 , 1 lo-12 10-11 . I 1 1 1 11 1 ~, 1 1 1 ~I I lo-lo C2H6 MOLE FRACTION FIGURE C.ll (Continued) 10 9 10-8

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199 incorrect, even in the lower stratosphere. The results in Figures C.10 and C.ll indicate that the two-dimensional and one-dimensional models agree better with one another than with the measurements of CFC13 and CF2C12. The models all appear to underestimate the rates for photolytic destruction of these gases in the lower stratosphere, leading to excessive concentra Lions at all latitudes and to an overestimate of global mean lifetimes. The models consequently predict excessive concentrations of chlorine, at steady state, in response to long-term industrial release. This matter is of con- siderable interest, and the difficulty cannot be blamed on the restrictive nature of one-dimensional models. Chemistry at High Latitudes There is a growing body of evidence that concentrations of NO and NOk are sharply reduced at high latitudes in winter (Noxon 1975, 1979, Coffey et al. 1981), although detailed concentration profiles are not available. Present chemical models (both one-dimensional and two-dimensional) predict column abundances of NO and NOk that are 3 to 5 times as large as those observed above 45 latitude. Hence in present models ozone is slowly consumed below 30 km during the period when it should be building up to the spring maximum. Simulations carried out by M. Ko and N.D. Sze (Atmospheric and . . F.nv i ronmental Research, Inc., personal communication, 1981) confirm that this slow chemistry suppresses the spring maximum in ozone at least for their model. The influence is significant even at midlatitudes and extends into early summer. The discrepancy implies a major defect in our understanding of the chemistry of NOx species. Detailed in situ measurements at high latitudes are mar ; ~ ~" are hm ',n~ - rotund the chemistry of this 1 1 ~ a_ ~ ~ ~ ~ ~ 1~ _ _ ~ ~ ~ ~ at low temperature. one area of weakly bound species like important region. Data on C10, NO, NO2, and HNO3 would be especially revealing. Laboratory measurements are needed to better define the chemistry of NOk species - of interest is the stability ClNO3 and HNO4, which may become major species at cold temperatures and low levels of light (cf. Prather et al. '979, Fox et al. 1982).

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200 Chemistry of Key Radicals Atmospheric observations cannot now provide a definitive test for current modelse Measurements of key species such as OH and O are lacking below 30 km, and few sets of simultaneous measurements exist for reactive species in the important families OK, HOk, NOk, and C1X. There are some hints that major discrepancies may emerge as better data are obtained. The difference between observed and calculated C1O at 40 km is particu- larly troubling, since the discrepancy lies near the peak for catalysis by reaction (20). The distribution of ethane departs from the pattern exhibited by other atmospheric halocarbons and hydro- carbons, in that models predict significantly lower concentrations than observed in the middle stratosphere (see Figure C.ll). Since reaction with C1 atoms is a major sink for C2H6 in the lower stratosphere, the observations suggest that models may overestimate the concentrations of C1 below 30 km. There are possible discrepancies for several other important species, including NO (see Figure C.3). SUMMARY STATEMENT Present models predict lower concentrations of stratospheric OH than models in use during the previous NRC study (NRC 1979). This change reflects new data on rates for reactions between OH, HNO3, and HNO4, which provide important pathways for recombination of odd hydrogen radicals in the lower stratosphere. Reduced estimates for OH concentrations imply sharply lower values for the concentration of C1O and higher values for NO and NO2 below 35 km. Agreement between model results and observations is significantly improved by using new kinetic data, but several potentially important ~ . . . cllscrepancles remain. Models predict that stratospheric ozone should decline by about 6 percent as the stratospheric chlorine concentration increases from current levels (3 ppb) to the asymptotic level (11 ppb) expected from industrial release of chlorofluorocarbons. Most of the ozone reduction is predicted to occur above 30 km, where transport is relatively unimportant. Hence, with current chemistry, results of chlorine perturbation studies are nearly model-independent.

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201 Additions of odd nitrogen to the stratosphere produce relatively large reductions in stratospheric ozone, according to current models. This matter is of some concern since the abundance of atmospheric N2O (the major precursor of NOX) is increasing. Ozone reductions due to NOX are distributed uniformly with altitude, affecting the ozone concentration as low as 20 km. Predictions for these ozone perturbations are quite sensitive to details of the transport mechanisms used in the model. REFERENCES Anderson, J.G., H.J. Grassl, R.E. Shetter, and J.J. Margitan (1980) Stratospheric free chlorine measured by balloon-borne in-situ resonance fluorescence. Journal of Geophysical Research 85:2869-2887. Chapman, S. (1930) A theory of upper atmospheric ozone. Memoirs of the Royal Meteorological Society 3:103-125 Coffey, M.J., W.G. Mankin, and A. Goldman (1981) Simultaneous spectroscopic determination of the latitudinal, seasonal, and diurnal variability of stratospheric N2O, NO, NO2, and HNO3. Journal of Geophysical Research 86:7331-7342. Crutzen, P. (1974) A review of upper atmospheric photo- chemistry. Canadian Journal of Chemistry 52:1569-1581. Dopplick, T.G. (1972) Radiative heating of the global atmosphere. Journal of Atmospheric Sciences 29:1278-1294. . Fox, J.L., S.C. Wofsy, M.B. McElroy, and M.J. Prather (1982) A stratospheric chemical instability. (To be submitted to Journal of Geophysical Research.) Goldan, P.D., W.C. Kuster, D.L. Albritton, and A.L. Schmeltekopf (1980) Stratospheric CFC13, CF2C12 and N2O height profile measurements at several latitudes. Journal of Geophysical Research 8S:413-423. Harwood, R.S. and J.A. Pyle (1980) The dynamical behavior of a two dimensional model of the stratosphere. Quarterly Journal of the Meteorological Society 106:395-420. Horvath, J.J. and C.J. Mason (1978) Nitric oxide mixing ratios near the stratopause measured by a rocket-borne chemiluminescent detector. Geophysical Research Letters 5:1023-1026. Hudson, R.D. and E.I. Reed, eds. (1979) The Stratosphere: Present and Future. NASA Reference Publication 1049.

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202 Greenbelt, Md.: National Aeronautics and Space Administration; N80-14641-14648. Springfield, Va.: National Technical Information Service. Hudson, R.D., et al., eds. (1982) The Stratosphere 1981. Theory and Measurements. WHO Global Research and Monitoring Project Report No. 11. Geneva: World Meteorological Organization. (Available from National Aeronautics and Space Administration, Code 963, Greenbelt, Md. 20771.) Hunten, D.M. (1975) Vertical transport in atmospheres. Pages 59-72, Atmospheres of Earth and the Planets, edited by B.M. McCormac. Boston, Mass.: D. Reidel. Johnston, H.S., D. Katterhorn, and G. Whitten (1976) Use of excess carbon 14 data to calibrate models of stratospheric ozone depletion by supersonic transport. Journal of Geophysical Research 81:368-380. Krey, P.W., R.J. Lagomarsino, and L.E. Toonkel (1977) Gaseous halogens in the atmosphere in 1975. Journal of Geophysical Research 82:1753-1766. Lazrus, A.L. and B.W. Gandrud (1974) Stratospheric sulphate aerosols. Journal of Geophysical Research 79:3424-3430. List, R.J. and K. Telegadas (1969) Using radioactive tracers to develop a model of the circulation of the stratosphere. Journal of Atmospheric Sciences 26:1128-1136. Littlejohn, D. and H.S. Johnston (1980) Rate constants for the reaction of hydroxyl radicals and peroxynitric acid. EOS Transactions of the American Geophysical Union 61:966. Logan, J.A., M.J. Prather, S.C. Wofsy, and M.B. McElroy (1978) Atmospheric chemistry: Response to human influence. Philosophical Transactions of the Royal Society 290:187-234. Luther, F.M. (1974) Large Scale Eddy Transport. Lawrence Livermore 2nd Annual Report, DOT-CIAP Program, UCRL-51336-74. Livermore, Calif.: University of California Radiation Laboratory. McConnell, J.C. and W.F.J. Evans (1978) Implications of low stratospheric hydroxyl concentrations for CFM and SST scenario calculations of ozone depletion. EOS Transactions of the American Geophysical Union 59:1078. McElroy, M.B.(1976) Chemical processes in the solar system: A kinetic perspective. Pages 127-211, MTP International Review of Science, Series 2, Volume 9, edited by D.R. Herschbach. London: Butterworths. .

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203 McElroy, M.B. (1980) Sources and sinks for nitrous oxide Pages 345-364, Proceedings of the NATO Advanced Study Institute on Atmospheric Ozone: Its Variation and Human Influences, edited by A.C. Aiken. October 1-13, 1979. U.S. Department of Transportation Report No. FAA-EE-80-20. Washington, D.C.: Federal Aviation Administration. McElroy, M.~., J.W. Elkins, S.C. Wofsy, and Y.L. Yung (1976) Sources and sinks for atmospheric N2O. Reviews of Geophysics and Space Physics 14:143-150. Miller, C., D.L. Filkin, A.J. Owens, J.M. Steed, and J.P. Jesson (1981) A two dimensional model of stratospheric chemistry and transport. Journal of Geophysical Research 86:12,039-12,065. Molina, L.T. and M.J. Molina (1981) W absorption cross sections of HO2NO2 vapor. Journal of Photochemistry 15:97-108. Murgatroyd, R.J. and F. Singleton (1961) Possible meridional circulations in the stratosphere and mesosphere. Quarterly Journal of the Royal Meterological Society 87:125. National Aeronautics and Space Administration (1981) Chemical kinetic and photochemical data for use in stratospheric modelling. Evaluation Number 4, NASA Panel for Data Evaluation, JPL Publication 81-3. Pasadena, Calif.: Jet Propulsion Laboratory. National Research Council (1979) Stratospheric Ozone Depletion by Halocarbons: Chemistry and Transport. Panel on Chemistry and Transport, Committee on Impacts of Stratospheric Change, Assembly of Mathematical and Physical Sciences. Washington, D.C.: National Academy of Sciences. Nelson, H.H., W.J. Marinelli, and H.S. Johnston (1981) The kinetics and product yield of the reaction of OH with HNO3. Chemical Physics Letters 78: 495-499. Noxon, J.F. ( 1975) NO2 in the stratosphere and troposphere measured by ground based absorption spectroscopy. Science 189: 547-549. Noxon, J.F. (1979) Stratospheric NO2. II. Global behavior. Journal of Geophysical Research 84: 5067-5076. Pierotti, D. and R.A. Rasmussen (1976) Combustion as a source of nitrous oxide in the atmosphere. Geophysical Research Letters 3: 265-267. Prather, M.J., M.B. McElroy, S.C. Wofsy, and J.A. Logan (1979) Stratospheric chemistry: Multiple solutions. Geophysical Research Letters 6: 163-164. .

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204 Rasmussen, R.A. and M.A.K. Khalil (1981) Atmospheric methane: Trends and seasonal cycles. Journal of Geophysical Research 86:9826-9832. Ridley, B.A. and D.R. Hastie (1981) Stratospheric odd-nitrogen: NO measurements at 51N in summer. Journal of Geophysical Research 86:3162-3166. Ridley, B.A. and H.I. Schiff (1981) Stratospheric odd nitrogen: Nitric oxide measurements at 32N in autumn. Journal of Geophysical Research 86:3167-3172. Rowland, F.S. and M.J. Molina (1975) Chlorofluoromethane in the environment. Reviews of Geophysics and Space Physics 13:1-3S. Steed, J.M., A.J. Owens, C. Miller, D.L. Filkin, and J.P. Jesson (1982) Two dimensional modelling of potential ozone perturbations by chlorofluorocarbons. Nature 295:308-311. Stolarski, R.S. and R.J. Cicerone (1974) Stratospheric chlorine: Possible sink for ozone. Canadian Journal of Chemistry 52:1610-1615. Sze, N.D. and M.K.W. Ko (1981) The effects of the rate or OH and HNO3 and HONO2 photolysis on the stratospheric chemistry. Atmospheric Environment 15:1301. Telegadas, K. and G.J. Ferber (1975) Atmospheric concentrations and inventory of Krypton-85 in 1973. Science 190:882-883. Turco, R.P., R.C. Whitten, O.B. Toon, E.C.Y. Inn, and P. Hamill (1981) Stratospheric hydroxyl radical concentrations: New limitations suggested by observations of gaseous and particulate sulfur. Journal of Geophysical Research 86:1129-1140. Weinstock, E.M., M.J. Phillips, and J.G. Anderson (1981) In-situ observations of C1O in the stratosphere: A review of recent results. Journal of Geophysical Research 86:7273-7278. Weiss, R.F. (1981) The temporal and spatial distribution of tropospheric nitrous oxide. Journal of Geophysical Research 86:7185-7196. Weiss, R.F. and H. Craig (1976) Production of atmospheric nitrous oxide by combustion. Geophysical Research Letters 3:751-753. Wine, P.H., A.R. Ravishankara, N.M. Kreutter, R.C. Shah, J.M. Nicovich, and R.L. Thompson (1981) Rate of reaction of OH with HNO3. Journal of Geophysical Research 86:1105-1112.

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205 Wofsy, S.C. (1978) Temporal and latitudinal variations of stratospheric trace gases: A critical comparison between theory and experiment. Journal of Geophysical Research 83:364-378. Wofsy, S.C. and M.B. McElroy (1974) HOk, NOk and ClOX: Their role in atmospheric photochemistry. Canadian Journal of Chemistry 52:1582-1591. Zipf, E.C. and S.S. Prasad (1980) Production of nitrous oxide in the auroral D and E regions. Nature 287:525-526.