Wavelength-dependent isotope fractionation in visible light O<sub>3</sub>
 photolysis and atmospheric implications

Früchtl, Marion; Janssen, Christof; Taraborrelli, Domenico; Gromov, Sergey; Röckmann, Thomas

doi:10.1002/2015gl066219

“…Initial evidence for this comes from laboratory experiments (Bhattacharya and Thiemens, 1988;Chakraborty and Bhattacharya, 2003), and was recently substantiated by measurements where photolytic O 3 removal could be analytically separated from chemical removal (Früchtl et al, 2015a). Wavelengthdependent isotope effects in O 3 photolysis are also suggested by theoretical calculations (Miller et al, 2005;Liang et al, 2006;Ndengué et al, 2014), but the agreement of these calculations with new high-precision measurements is relatively poor (Früchtl et al, 2015b). Nevertheless, isotope effects in photolysis have been suggested as an explanation for the high enrichments found by balloon measurements in the upper stratosphere (Haverd et al, 2005;Krankowsky et al, 2007), where the effects of the formation reaction fall short of the observed enrichments by 2-4 %.…”

Section: Introductionmentioning

confidence: 99%

Retrievals of heavy ozone with MIPAS

Jonkheid

¹

,

Röckmann

²

,

Glatthor

³

et al. 2016

Self Cite

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Abstract. A method for retrieval of 18 O-substituted isotopomers of O 3 in the stratosphere with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is presented. Using a smoothing regularisation constraint, volume mixing ratio profiles are retrieved for the main isotopologue and the symmetric and asymmetric isotopomers of singly substituted O 3 . For the retrieval of the heavy isotopologues, two microwindows in the MIPAS A band (685-970 cm −1 ) and six in the AB band (1020-1170 cm −1 ) are used. As the retrievals are performed as perturbations on the previously retrieved a priori profiles, the vertical resolution of the individual isotopomer profiles is very similar, which is important when calculating the ratio between two isotopomers. The performance of the method is evaluated using 1044 vertical profiles recorded with MIPAS on 1 July 2003.The mean values are separated by latitude bands, along with estimates of their uncertainties. The asymmetric isotopomer shows a mean enrichment of ∼ 8 %, with a vertical profile that increases up to 33 km and decreases at higher altitudes. This decrease with altitude is a robust result that does not depend on retrieval settings, and it has not been reported clearly in previously published datasets. The symmetric isotopomer is considerably less enriched, with mean values around 3 % and with a large spread. In individual retrievals the uncertainty of the enrichment is dominated by the measurement noise (2-4 %), which can be reduced by averaging multiple retrievals; systematic uncertainties linked to the retrieval are generally small at ∼ 0.5 %, but this is likely underestimated because the uncertainties in key spectroscopic parameters are unknown. The variabilities in the retrieval results are largest for the Southern Hemisphere.

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“…These issues are important in determining the atmospheric ozone isotope composition and as input to the ozone isotope transfer models. A recent study by Früchtl et al () in visible light photolysis was done using two wavelength ranges: (i) over a broad range of 455 to 800 nm giving average values of isotopic fractionation ranging from −15.2‰ to −26.9‰ and (ii) in three narrow band wavelengths of 530, 617, and 660 nm which gave values of −12.9‰, −15.0‰, and −23.9‰, respectively. These results are also in conflict with the model predictions for the visible light, both in magnitude and directions.…”

Section: Motivationmentioning

confidence: 99%

“…In the stratosphere, the dominant processes controlling the isotopic composition of ozone are two: formation and photolysis. The isotopic effects due to the former have been well established (Brenninkmeijer et al, ; Gao & Marcus, ; Janssen et al, , ; Mauersberger et al, ; Morton et al, ; Thiemens, ; Thiemens & Heidenreich, ), but understanding the changes due to photolysis is still unsatisfactory (Bhattacharya & Thiemens, ; Chakraborty & Bhattacharya, ; Früchtl et al, ; Wen & Thiemens, ). The reason is that photolysis of ozone in laboratory is always associated with two secondary interfering processes: formation of fresh ozone and ozone dissociation through reactive atomic and molecular oxygen species, which are formed due to the photolysis itself.…”

Section: Introductionmentioning

confidence: 99%

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Isotopic Fractionation in Photolysis of Ozone in the Hartley and Chappuis Bands

Huang

¹

,

Bhattacharya

²

,

Hsieh

³

et al. 2019

Earth and Space Science

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The isotopic enhancement of atmospheric ozone (O3) is mainly determined by two processes of formation and photolytic decomposition. The formation is known to be associated with isotopic fractionation which can be as high as 120‰ relative to the parent oxygen. Photolysis‐induced isotopic fractionation in O3, however, is not known accurately. Absorption cross sections of various ozone species have been calculated by Zero Point Energy‐based model and quantum mechanical wave packet model. But their predictions pertaining to isotopic fractionations have not been verified experimentally. In the present work, we performed irradiation experiments of O3 at several wavelengths in the Hartley and Chappuis bands and determined the dissociative isotopic fractionation factors by a Rayleigh distillation model. In laboratory conditions, photolysis of ozone produces reactive atomic and/or molecular oxygen which influence the dissociative process through secondary chemistry. The complex interplay of primary photolysis and secondary chemistry was tracked by a kinetic model, and isotopic fractionation factors associated with photolysis alone were derived within a range of uncertainties. The fractionations are found to depend on the photon wavelength and deviate significantly at some wavelengths from the predicted values. For example, at 254 nm the zero point energy‐based models predict lower photolysis rate coefficients for the lighter isotopic species; the present data show about 50‰ higher values.

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“…Initial evidence for this comes from laboratory experiments (Bhattacharya and Thiemens, 1988;Chakraborty and Bhattacharya, 2003), and was recently substantiated by measurements where photolytic O 3 removal could be analytically separated from chemical removal (Früchtl et al, 2015a). Wavelengthdependent isotope effects in O 3 photolysis are also suggested by theoretical calculations (Miller et al, 2005;Liang et al, 2006;Ndengué et al, 2014), but the agreement of these calculations with new high-precision measurements is relatively poor (Früchtl et al, 2015b). Nevertheless, isotope effects in photolysis have been suggested as an explanation for the high enrichments found by balloon measurements in the upper stratosphere (Haverd et al, 2005;Krankowsky et al, 2007), where the effects of the formation reaction fall short of the observed enrichments by 2-4 %.…”

Section: Introductionmentioning

confidence: 99%

Response to Anonymous Referee #1

Jonkheid¹

2016

0

View full text Add to dashboard Cite

A method for retrieval of 18 O-substituted isotopomers of O 3 in the stratosphere with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is presented. Using a smoothing regularisation constraint, volume mixing ratio profiles are retrieved for the main isotopologue and the symmetric and asymmetric isotopomers of singly substituted O 3 . For the retrieval of the heavy isotopologues, two microwindows in the MIPAS A band (685-970 cm −1 ) and six in the AB band (1020-1170 cm −1 ) are used. As the retrievals are performed as perturbations on the previously retrieved a priori profiles, the vertical resolution of the individual isotopomer profiles is very similar, which is important when calculating the ratio between two isotopomers. The performance of the method is evaluated using 1044 vertical profiles recorded with MIPAS on 1 July 2003.The mean values are separated by latitude bands, along with estimates of their uncertainties. The asymmetric isotopomer shows a mean enrichment of ∼ 8 %, with a vertical profile that increases up to 33 km and decreases at higher altitudes. This decrease with altitude is a robust result that does not depend on retrieval settings, and it has not been reported clearly in previously published datasets. The symmetric isotopomer is considerably less enriched, with mean values around 3 % and with a large spread. In individual retrievals the uncertainty of the enrichment is dominated by the measurement noise (2-4 %), which can be reduced by averaging multiple retrievals; systematic uncertainties linked to the retrieval are generally small at ∼ 0.5 %, but this is likely underestimated because the uncertainties in key spectroscopic parameters are unknown. The variabilities in the retrieval results are largest for the Southern Hemisphere.

show abstract

Wavelength-dependent isotope fractionation in visible light O₃ photolysis and atmospheric implications

Cited by 8 publications

References 34 publications

Retrievals of heavy ozone with MIPAS

Retrievals of heavy ozone with MIPAS

Isotopic Fractionation in Photolysis of Ozone in the Hartley and Chappuis Bands

Response to Anonymous Referee #1

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Wavelength-dependent isotope fractionation in visible light O3 photolysis and atmospheric implications

Cited by 8 publications

References 34 publications

Retrievals of heavy ozone with MIPAS

Retrievals of heavy ozone with MIPAS

Isotopic Fractionation in Photolysis of Ozone in the Hartley and Chappuis Bands

Response to Anonymous Referee #1

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Wavelength-dependent isotope fractionation in visible light O₃ photolysis and atmospheric implications