The Nighttime Distribution of Ozone in the Low-Latitude Mesosphere

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1 Pure and Applied Gephysics (PAGEOPH) Vl (1973/V-VII) BirkMuser Verlag, Basel The Nighttime Distributin f Ozne in the Lw-Latitude Messphere By R. G. ROBLE 1) and P. B. HAYS 2) Abstract - The intensity f stars at wavelengths in the Hartley cntinuum regin f zne has been mnitred by the University f Wiscnsin stellar phtmeters abard the OAO-2 satellite during ccultatin f the star by the earth's atmsphere. These ccultatin data have been used t determine the zne number density prfile at the ccultatin tangent pint. The nighttime zne number density prfile has a bulge in its vertical prfile with a peak f 1 t 3 x 10' cm -3 at apprximately 83 km and2a minimum near 75 kin. The zne number density at high altitudes varies by as much as a factr f 4, but des nt shw any clear seasnal variatin r nighttime variatin. The retrieved zne number density prfiles define a data envelpe that is cmpared with ther nighttime bservatins f the zne number density prfile and als the results f theretical mdels. Calculatins are als presented that illustrate the difference in retrieving the bulge in the zne number density prfile frm stellar and slar ccultatin data. 1. Intrductin Stellar intensity measurements, in certain ultravilet atmspheric absrptin bands, made by a satellite during ccultatin f the star by the earth's atmsphere, can be used t btain the lcal number density f the absrbing species at the ccultatin tangent pint (HAYS and ROBLE [8-9]). During the past few years the Orbiting Astrnmical Observatry (OAO-2) has been used t make these ccultatin intensity measurements using bright ultravilet stars (HAYs et al. [12]). The ccultatin technique is based n classical ultravilet absrptin spectrscpy. The star is the surce f ultravilet light and the stellar phtmeters abard the OAO-2 satellite are the detectrs. The atmsphere between the star and the detectrs acts as the absrptin cell. During the ccultatin prcess, the stellar light passes thrugh prgressively denser regins f the atmsphere and the ultravilet light is absrbed due t the strng absrptin features f certain atmspheric gases. The basic measurement is thus the stellar intensity as a functin f time, but by knwing the star's psitin and the satellite rbital elements, the intensity is related t the tangent ray height f the cculting star. If absrptin is due t a single species, the nrmalized stellar intensity is directly related t the tangential 1) Natinal Center fr Atmspheric Research, Bulder, Clrad (The Natinal Center fr Atmspheric Research is spnsred by the Natinal Science Fundatin.) z) Department f Atmspheric and Oceanic Sciences, University f Michigan, Ann Arbr, Michigan

2 1282 R.G. Rbte and P. B. Hays (Pageph, clumn number density f the absrbing species thrugh Beer's Law (HAYS and ROBLE [10]). The data giving the tangential clumn number density as a functin f tangent ray height are directly inverted, using the technique described by ROBLE and HAYS [22] t btain the lcal number density prfile f the absrbing species at the ccultatin tangent pint. Occultatin measurements made in the Schumann-Runge cntinuum f mlecular xygen near 1500 A have been used t btain the mlecular xygen number density prfile in the lwer thermsphere. These measurements have been discussed by HAYS and ROBLE [10]. The nighttime number density prfile f zne in the messphere has als been determined frm stellar intensity measurements made in the Hartley cntinuum regin f zne near 2500 A_. The results f these measurements are discussed by HAYS and ROBLE [l 1]. In this paper, we cmpare the results f the OAO-2 zne measurements with thery and ther nighttime zne measurements. We als present the results f a single ccultatin scan and discuss the difference in retrieving the zne number density bulge near 80 km frm slar and stellar ccultatin data. 2. Stellar ccultatin scan The zne and mlecular xygen absrptin crss sectins and the transmissin functin f the varius ultravilet filters used with the OAO-2 stellar phtmeters fr the ccultatin measurements are shwn in Fig. 1. Filter (4-1) is lcated in the Schumann-Runge cntinuum regin f mlecular xygen and is used t btain the mlecular xygen number density in the lwer thermsphere. Filters (2-5) and (3-2) are in the Hartley cntinuum regin f zne and are used t btain the zne number density prfile in the messphere. Filter (1-4) is used t measure the zne number density in the stratsphere. The results presented in this paper were determined frm ccultatin data btained by the OAO-2 stellar phtmeters using filters (2-5) and (3-2). HAyS and ROBLE [9] have shwn that stellar ultravilet light near 2500 A is primarily absrbed by zne in the earth's atmsphere and stellar ccultatin measurements within this wavelength regin can be used t btain the zne number density prfile in the 60 t 100 km altitude interval. In the lwer prtin f the altitude interval rayleigh scattering and mlecular xygen absrptin in the Herzberg cntinuum have small cntributins t the ttal attenuatin. These cntributins are eliminated frm the data as discussed by HAYS and ROBLE [10]. The intensity spectrum f the star abve the earth's atmsphere is measured by an ultravilet spectrmeter abard the OAO-2 satellite. A typical star spectrum, btained n rbit n 3 April, 1971, is shwn in Fig. 2. The slar spectrum is als shwn in Fig. 2 fr cmparisn. The nrmalized signal f this star, measured during ccultatin using the OAO-2 stellar phtmeter with filter (3-2), is shwn in Fig. 3a. Belw 100 km the signal decreases due t absrptin by zne. The decrease in the signal cntinues

3 Vl , 1973/V-VII) The Nighttime Distributin f Ozne 1283 until an altitude f abut 83 kin, then a slight increase in the signal ccurs reaching a maximum arund 75 kin. Belw 75 km the signal decreases again until ccultatin near 45 kin. The zne number density prfile at the ccultatin tangent pint is btained frm the intensity data using the inversin scheme described by ROBLE and HAYS [22] i-rz ~ i0-19 w GO IJ io-zj t000 Schumann-Runge /~--"-\ Cntinuum (0 z) / \ Hartley Cntinuum \\ \ I/ -\ (0 s) \\ / \ \ / / \ "\ "~\ // \\ \,I \ k,l L. Herzberg(Oz)[ % \ P"\ \, u -Ru0e,I \, / GO ~HuggmsBands P. ;~. (03) - Ill / \ /,-2. '~ '~ (4-I) I! (2-5)(3-2) ([-4) / \ '1 // "\ \ / \ ' I \, Y V'\, \\ / i \ i,, 't" I 1% ", I ",,I ~ WAVEI..ENGTH (.~) I IO z 0.6Q: ~ 04wG 'F,.~ O.2'T ~ Figure 1 Absrptin crss-sectins fr mlecular xygen and zne. The dashed curves give the transmissin functins fr the filters used with the OAO-2 stellar phtmeters. Filter (4-1) is used t btain the mlecular xygen number density in the lwer thermsphere and Filters (2-5), (3-2) and (1-4) are used t determine the zne number density in the messphere ~ 600 ~ 500 w 400 i ] { i i i... SOLAR / --STELLAR /~/- / /// / \/ / i013 0~ IO 12 ~ I00 i0~ bj 0 ~ I I I / I [ I jlo WAVE LENGTH (A) Figure 2 Slid curve is the stellar intensity as a functin f wavelength measured by the OAO-2 spectrmeter prir t ccultatin n rbit This star was used t btain the ccultatin data shwn in Fig. 3. The dashed curve is the slar spectrum btained frm ACKERMAN [1]

4 1284 R.G. Rble and P. B. Hays (Pageph, and HAYS and ROBLE [10] and is shwn in Fig. 3b. The dip in the nrmalized intensity curve near 80 kin, shwn in Fig. 3a, is due t a bulge in the zne number density distributin at that a!titude. The peak zne number density at the bulge is 3 10 a cm -3 at 83 km. The minimum ccurs near 73 kin, hwever, the magnitude f the number density at that altitude is difficult t determine. A cmplete discussin f accuracy f the inversin scheme and an analysis f errrs in the ccultatin measurements have been given by ROBLE and HAYS [22]. Ii I O 70 I I I I- i I I I I 2460/~ FILTER... OAO 2 DATA MODEL 03 PROFILE - - CALCULATED STELLAR, '// SIGNAL "~.1 / --- CALCULATED SOLAR /~; I10 I00 9O 8O TO,,,,,,,,i ~,;,,~,,,i,,,,~,,,i,,,, ~,... RETRIEVED 03 PROFILE FROM OAO-2 DATA "~ 6 I : / 5 2! s (.~ ,- ~0, 12!3, ' '5!~ i, '8!9,....,,,,,, NORMALIZED INTENSITY (I(rt)/I~) OZONE NUMBER DENSITY (cni 3) i r 10" Figure 3a. Figure 3b. Figure 3 a) The dts give the nrmalized intensity as a functin f tangent ray height measured by the OAO-2 stellar phtmeters using the 2460 A filter. The gegraphic psitin f the ccultatin tangent pint is 35~ 114~ and time is LMT n 3 April, The slid and dashed curves are the calculated nrmalized intensities fr a stellar and slar ccultatin respectively using the mdel zne prfile in Fig. 3b. b) The dts give the retrieved zne number density prfile frm the OAO-2 ccultatindata shwn in Fig. 3a. The slid curve is the mdel zne number density prfile used t calculate the stellar and slar intensity prfiles in Fig. 3a 3. Stellar vs. slar ccultatin The zne number density prfile has als been determined frm slar ccultatin measurements made frm a satellite (RAWCLIFFE et al. [20], MmLER and STEWART, [18]). If the intensity frm the entire slar disk is used during ccultatin the effect f the finite size f the sun must be cnsidered in analyzing the data. In this sectin we examine whether the bulge in the zne number density near 80 km can be determined frm slar ccultatin measurements when the entire slar disk is used as the surce. Fr simplicity a mdel f the zne number density prfile is used in these calculatins. The zne prfile is apprximated by a sum f gaussian and expnential functins (ROBLE and HAYS [22]) and the prfile is shwn in Fig. 3b. The nrmalized intensity calculatins

5 Vl , 1973/V-VII) The Nighttime Distributin f Ozne 1285 fr a stellar ccultatin, using OAO-2 filter (3-2), are shwn in Fig. 3a. The intensity calculatins fr the bradband filter require a wavelength integratin ver the effective passband f the filter (HAYS and ROBLE [10]). Therefre, we use the stellar spectrum, shwn in Fig. 2, the zne absrptin crss-sectin and the filter transmissin functins, shwn in Fig. 1, t calculate the nrmalized ccultatin signal fr the mdel zne number density distributin. The calculated nrmalized intensity prfile is shwn in Fig. 3a and it has apprximately the same shape as the OAO-2 ccultatin data. The dip in the intensity curve defines the bulge in the zne number density prfile. Fr a slar ccultatin, the finite size f the sun must be cnsidered because the slar energy emitted frm different prtins f the slar disk is transmitted thrugh the //" 0985 "~\ // 097, / ,924 0, // O \ 0.9,4 / 0.9,2 / 95 km 83 krn -go km Figure 4 The calculated nrmalized intensity distributin acrss the slar disk at a tangent ray height f 83 kin. The satellite altitude at ccultatin is 715 km. The OAO-2 filter transmissin functin fr the 2460 filter is used in the calculatins. The tangent ray heights fr the upper and lwer slar limbs are als given in the figure earth's atmsphere at different tangent ray heights. The nrmalized intensity fr a slar ccultatin is calculated using the technique f ROBLE and NORTON [23] and is shwn in Fig. 3a. Fr these calculatins we used the slar energy spectrum, shwn in Fig. 2, the zne crss-sectin and the filter (3-2) transmissin functin shwn in Fig. 1. The dip in the intensity curve that ccurs in the stellar ccultatin case des nt appear in the slar ccultatin case. Frm nrmal satellite altitudes the tangent ray heights f the upper and lwer limb f the slar disk are separated by apprximately 25 km. Therefre a smearing f the intensity variatin caused by the bulge in the Ozne number density prfile ccurs when the entire slar disk is used during ccultatin and a dip in the intensity prfile is nt evident. The calculated nrmalized intensity variatin acrss the slar disk at a tangent ray height f 83 km fr the center f the slar disk is shwn in Fig. 4. The tangent ray height f the upper limb is 95 km and the lwer limb is 70 km. The intensity variatin caused by the bulge in the zne number density prfile at 83 km

6 1286 R.G. Rble and P. B. Hays (Pageph, ccurs near the center f the slar disk. The intensity structure acrss the slar disk is nt evident when the verall intensity frm the entire slar disk is measured during ccultatin. In thery, the structure in the zne number density prfile can be retrieved frm slar ccultatin data using the entire slar disk, with an iterative technique. Hwever, in practice, the iterative scheme is difficult t use especially in the presence f statistical nise. Better results wuld be btained if a small prtin f the slar disk is used fr the slar ccultatin measurements. 4. Cmparisn f results The zne number density prfiles frm twelve stellar ccultatins have been presented by HAYS and ROBLE [1 1 ]. The measurements indicate that messpheric zne has a variatin f as much as,a factr f 4 at high altitudes, but des nt shw any clear I10 ~ i i lil I i i i IElal I i i [ i i[ill~ I i I I Illl I I i i i iiii OAO-2 MEASUREMENTS (RANGE). RAWCLIFFET. AL. (1963) J I00 - ~ REED (1968) ] ~:~('~ [Z-2] CARVER ET. AL. (1972) (.A.GE) / - ~ E ~ ~, a MILLER AND STEWART ('9651_~ 90 ~ ~ ~ = = = HILSENRATH (F97F) ~ J EVANS AND LLEWELLYN / J~..~;~ / AM (19TO) / 8- ~? / ~-~ PM 3-28-G9 -t ~ ~ ~ --*--=--= TISONE (1972) / 11t ;;'~. WEEKS AND SMITH (1968) ] "~'~l~=:le,~_. ~... '~ ~ SEASONAL VARIATION (.9 -- ~ \ '~'\ HIGH LATITUDES.--~ 70 ~. ~ ~-- ~\\\ ~ r, _ EVANS AND LLEWELLYN ('9~2~ I ~.~v,,,lh \ ",,., % - (~ TWILIGHT, 0 ~ SOLAR / " ~ ~ " ~ \ ~ ' ~ ELEVATION ANGLE)._] 60'-- ". ". 40 I I IIII I I I IIIII] I I J IIIIII I I I Illlll I ",[ I I I I'%%J] i 10 7 IO i0 I0 i0 li i0 i2 OZONE NUMBER DENSITY (cm -3) Figure 5 Cmparisn f the OAO-2 zne data envelpe with the nighttime zne number density prfiles determined by varius bservers seasnal r nighttime variatin. A slight increase in the altitude f the bulge in the zne number density prfile appears t be assciated with increasing latitude. These measurements plus a few additinal nes are used t define an envelpe representing the zne number density prfiles determined frm the OAO-2 stellar ccultatin measurements. The envelpe is shwn in Fig. 5 alng with nighttime and twilight zne prfiles

7 Vl , 1973/V-VII) The Nighttime Distributin f Ozne 1287 determined by ther experimenters. At high altitudes there is gd agreement with the zne number density prfiles determined by the OAO-2 satellite and the prfiles deduced by EVANS and LLEWELLYN [5-6]. Between 60 and 75 kin, the data f EVANS and LLEWELLYN [5--6], EVANS et al. [7], WEEKS and SMITH [26], MILLER and STEWART [18], TISONE [25] and RAWCLIFFE et al. [20] are clustered alng the upper limb f the OAO-2 zne data envelpe. Belw 60 kin, the OAO-2 zne data envelpe des nt agree with the results f CARVER et al [3-4], REED [21] and H~LSENRATH [I4]. This departure frm the ther bservatins is prbably due t the difficulty f retrieving the zne number E 120 I00 8O r i iiiiii I l i i irllll I i i IIIIH I 1 [iiiiii I i lllllll... HESSTVEDT (19681 OAO-2 DATA ENVELOPE ; : : SHIMAZAKI AND LAIRD (1972) ~ ~ ~- x BOWMAN ET. AL. (1970) ~ :-'~'J~..~ " "Tl..r ~, : " HUNT (197l), ~ i p ~,, J M LEOVY (1969) L : ~ e ~ - ~ ~ HUNT (1966} I-- 60 "1- (.9 I..IJ "r 4O 20 0 I I tl)nanl I atillinl I I IIIllll t t nnln))l ) a ++lllzj I i li[llll I io I0 io II i I I II)11 i014 OZONE NUMBER DENSITY (cm -3) Figure 6 Cmparisn f the OAO-2 zne data envelpe with the zne number density prfile determined frm varius theretical mdels density at lw signal levels in the presence f statistical nise. ROBLE and HAYS [22] shw that the zne number density is best retrieved between nrmalized ccultatin data values f Therefre, the zne number density prfile determined frm the OAO-2 ccultatin measurements are limited t the km altitude interval. In Fig. 6 the OAO-2 zne data envelpe is als cmpared with the zne number density prfile determined frm varius theretical mdels. In general, there is a large variatin between the varius theretical mdels. Hwever, the general features f the OAO-2 zne measurements appear t be present in the results f theretical predictins which utilize a mist atmsphere in which hydrgen cmpunds are cnsidered in the chemistry.

8 1288 R.G. Rble and P. B. Hays (Pageph, Acknwledgement We thank K. S. HANSEN fr prgramming assistance and A. N. SHAH fr btaining the data. This wrk was supprted in part by NASA Grant NGR and NASA cntract NAS We wish t acknwledge the helpful supprt f Dr. HOUK and the OAO Wiscnsin and NASA experimental team. REFEREN CES [1 ] M. ACKERMAN, Ultravilet slar radiatin related t messpherie prcesses, Aern. Acta. A (1972), N. 77. [2] M. R. BOWMAN, L. THOMAS and J. E. GEISLER, The effect f diffusin prcesses n the hydrgen and xygen cnstituents in the messpher e and lwer thermsphere, J. Atms. Terr. Phys. 32 (1970), [3] J. H. CARVER, B. H. HORTON and F. G. BURGER, Rcket determinatin f the night zne distributin and the lunar ultravilet flux, Space Res. 7 (1967), ] J. H. CARVER, B. H. HORTON, R. S. O'BRIEN and B. ROFE, Ozne determinatins by lunar rcket phtmetry, Planetary Space Sci. 20 (1972), 217. [5] W. F. J. EVANS and E. J. LLEWELLYN, Mlecular xygen emissins in the airglw, Ann. Gephys. 26 (1970), 167. [6] W. F. J. EVANS and E. J. LLEWELLYN, Measurements fmesspherie zne frm bservatins f the 1.27lz band, Radi Sci. 7 (1972), 45. [7] W. F. J. EVANS, H. C. WOOD and E. J. LLEWELLYN, Grund-basedphtmetr~ic bservatins f the 1.27p band in the evening twilight, Planetary Space Sci. 18 (1970), [8] P.B. HAYS and R. G. ROBLE, Stellar spectra and atmspheric cmpsitin, J. Atms. Sci. 25 (1968a), [9] P. B. HaYs and R. G. ROBLE, Atmspheric prperties frm the inversin f planetary ccultatin data, Planetary Space Sci. 16 (1968b), [10] P. B. HaYs and R. G. ROBLE, Stellar ccultatin measurements f mlecular xygen in the lwer thermsphere, Planetary Space Sci (1972a), in press. [11] P. B. HAYS and R. G. ROBLE, Observatin fmesspheric zne at lw latitudes, Planetary Space Sci. (1972b), in press. [12] P. B. HAYS, R. G. ROBLE and A. N. SHAH, Terrestrial atmspheric cmpsitin frm stellar ccultatins, Science 176 (1972), 793. [13] E. HESSTVEDT, On the effect f vertical eddy transprt n atmspheric cmpsitin in the messphere and lwer thermsphere, Gephys. Nrv. 27 (1968), 1. [14] E- HILSENRATI-:I, Ozne measurements in the messphere and stratsphere during tw significant gephysical events, J. Atrns. Sci. 28 (1971), 295. [15] B. G. HUNT, Phtchemistry f zne in a mist atmsphere, J. Gephys. Res. 71 (1966), [16] B. G. HUNT, A diffusin phtchemical study f the messphere and lwer thermsphere and the assciated cnservatin mechanism, J. Atms. Terr. Phys. 33 (1971), [17] C. B. LEOVY, Atmspheric zne: An analytic mdel fr phtchemistry in the presence f water vapr, J. Gephys. Res. 74 (1969), 417. [18] D. E. MILLER and K. H. STEWART, Observatins f atmspheric zne frm an artificial earth satellite, Prc. Ry. Sc. Lndn A288 (1965), 540. [19] J. PARK, Oznephtehemistryandenergybudget in the middle atmsphere. Ph.D. thesis, University f Clrad, Bulder, Clrad (1972). [20] R. D. RAWCLIFFE, G. E. MELOY, R. M. FRIEDMAN and E. H. ROGERS, Measurement f vertical distributin f zne frm a plar rbiting satellite, J. Gephys. Res. 68 (1963), [21] E. I. REED, A night measurement f messpheric zne by bservatins f ultravilet airglw, J. Gephys. Res. 73 (1968), 2951.

Vl. 106-108, 1973/V-VII) The Nighttime Distributin f Ozne 1289 [22] R. G. ROBLE and P. B.

9 Vl , 1973/V-VII) The Nighttime Distributin f Ozne 1289 [22] R. G. ROBLE and P. B. HAYS, A technique fr recvering the vertical number density prfile f atmspheric gases frm planetary ccultatin data, Planetary Space Sci. 20 (1972), [23] R. G. ROBLE and R. B. NORTON, Thermspheric mlecular xygen frm slar EUV ccultatin measurements, J. Gephys. Res. 77 (1972), [24] T. SHIMAZAKI and A. R. LAmD, Seasnal effects n distributins f minr neutral cnstituents in the messphere and lwer thermsphere, Radi Sci. 7 (1972), 23. [25] G. C. TlSONE, Measurements f the absrptin f slar radiatin by 02 and 03 in the 2150-A regin, J. Gephys. Res. 77 (1972), [26] L. H. WEEKS and L. G. SMITH, A rcket measurement f zne near sunrise, Planetary Space Sci. 16 (1968), 1189.

Journal of Molecular EvOlution by Springer-Verlag. 1979

Journal of Molecular EvOlution by Springer-Verlag. 1979 0022-28447900140057~ 01.60 J. Ml. Evl. 14, 57--64 (1979) Jurnal f Mlecular EvOlutin by Springer-Verlag. 1979 Slar Radiatin Incident n the Martian Surface W.R. Kuhn and S.K. Atreya Department f Atmspheric