On the distribution of mesospheric molecular hydrogen inferred from HALOE measurements of H<sub>2</sub>O and CH<sub>4</sub>

Harries, J. E.; Ruth, Sarah; Russell, James M.

doi:10.1029/95gl03197

Cited by 30 publications

(22 citation statements)

References 26 publications

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Section: Analytic Solutions Of Equations In the Ancient And Modern mentioning

confidence: 99%

“…This balance allows an atmosphere to remain at a constant redox state, a condition that appears to mostly hold during the Phanerozoic as evidenced by the continuous presence of animals (Knoll & Carroll, 1999) and charcoal (Chaloner, 1989;Wildman et al, 2004), although minor deviations have likely occurred (Berner et al, 2003). The total hydrogen mixing ratio (as H 2 equivalents) above the modern tropopause is ∼6 ppmv (Harries et al, 1996), yielding a modern hydrogen escape flux of F E,NOW = 0.02 Tmol O 2 year −1 via equation 10. compiles the estimates we use to constrain modern values of the remaining parameters in equation 15. The rate of O 2 production during organic carbon sedimentation is estimated 10.0 ± 3.3 Tmol year −1 and the rate of O 2 use during weathering is estimated as 7.5 ± 2.5 Tmol year −1 , so we adopt the nominal values of F B,NOW = 10 Tmol year −1 and F W,NOW = 7 Tmol year −1 for the calculations below.…”

Section: Analytic Solutions Of Equations In the Ancient And Modern LImentioning

confidence: 99%

“…In the modern day, hydrogen escape is limited by the abundance of H-bearing compounds in the lower stratosphere (Walker, 1977;pp. 157-163) that contains ∼ 1.7 ppmv of CH 4 , 0.5 ppmv of H 2 , and 3 ppmv of H 2 O (Harries et al ., 1996). Unlike H 2 O, CH 4 does not condense in the troposphere, and hence can act as a quantitatively significant carrier of hydrogen to the upper atmosphere.…”

Section: Introductionmentioning

confidence: 99%

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Biogeochemical modelling of the rise in atmospheric oxygen

2006

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Understanding the evolution of atmospheric molecular oxygen levels is a fundamental unsolved problem in Earth's history. We develop a quantitative biogeochemical model that simulates the Palaeoproterozoic transition of the Earth's atmosphere from a weakly reducing state to an O2‐rich state. The purpose is to gain an insight into factors that plausibly control the timing and rapidity of the oxic transition. The model uses a simplified atmospheric chemistry (parameterized from complex photochemical models) and evolving redox fluxes in the Earth system. We consider time‐dependent fluxes that include organic carbon burial and associated oxygen production, reducing gases from metamorphic and volcanic sources, oxidative weathering, and the escape of hydrogen to space. We find that the oxic transition occurs in a geologically short time when the O2‐consuming flux of reducing gases falls below the flux of organic carbon burial that produces O2. A short timescale for the oxic transition is enhanced by a positive feedback due to decreasing destruction of O2 as stratospheric ozone forms, which is captured in our atmospheric chemistry parameterization. We show that one numerically self‐consistent solution for the rise of O2 involves a decline in flux of reducing gases driven by irreversible secular oxidation of the crust caused by time‐integrated hydrogen escape to space in the preoxic atmosphere, and that this is compatible with constraints from the geological record. In this model, the timing of the oxic transition is strongly affected by buffers of reduced materials, particularly iron, in the continental crust. An alternative version of the model, where greater fluxes of reduced hydrothermal cations from the Archean seafloor consume O2, produces a similar history of O2 and CH4. When climate and biosphere feedbacks are included in our model of the oxic transition, we find that multiple ‘Snowball Earth’ events are simulated under certain circumstances, as methane collapses and rises repeatedly before reaching a new steady‐state.

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Section: Analytic Solutions Of Equations In the Ancient And Modern mentioning

confidence: 99%

Section: Analytic Solutions Of Equations In the Ancient And Modern LImentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Biogeochemical modelling of the rise in atmospheric oxygen

2006

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“…The late vortex H 2 profile has structure not seen in the early vortex profile, in particular the large increase above 28 km. There are no direct measurements of H 2 in the mesosphere but H 2 has been inferred from H 2 O and CH 4 measurements by considering the total hydrogen budget [ Harries et al , 1996]. The inferred H 2 mixing ratios are greater than 1 ppmv only above 1 mb which is roughly the height of the stratopause.…”

Section: Mixing Inferred From Long‐lived Tracer‐tracer Correlationsmentioning

confidence: 99%

Descent and mixing in the 1999–2000 northern polar vortex inferred from in situ tracer measurements

et al. 2002

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[1] In situ measurements from the Lightweight Airborne Chromatograph Experiment (LACE) and the Airborne Chromatograph for Atmospheric Trace Species (ACATS-IV) taken during the SAGE III Ozone Loss and Validation Experiment (SOLVE) are used to examine the descent and mixing in the 1999-2000 northern stratospheric polar vortex. LACE was flown twice on an in situ balloon platform, in November 1999 just after the vortex formed and in March 2000 near the end of the vortex lifetime. The aim of this paper is to use simple models of vortex transport to try to explain the changes seen in the long-lived tracers measured by LACE between the two vortex flights. It is the high precision and long-term accuracy of the observations that allow small differences in the data from a number of species obtained on different flights to be used to infer transport processes. Changes in tracer profiles as a function of height or potential temperature can be attributed, to first order, to descent in the vortex. A calculation which used six tracers shows that the total descent was a strong function of potential temperature, from 200 K in the middle stratosphere to 50 K in the lower stratosphere over the nearly 4-month period between flights. Observed changes in long-lived tracer-tracer correlations require a mixing process to have occurred since descent alone cannot change the correlations. Two simple models of mixing are used to examine the tracer correlation changes. One model simulates entrainment of midlatitude air across the vortex edge with relatively efficient mixing within the vortex. A second model simulates the effect of differential descent and subsequent efficient mixing within a vortex that is entirely isolated from the midlatitudes. It is shown that the differential descent and mixing calculation produces results which are much more consistent among all the tracer correlations compared to the results from midlatitude entrainment. The unique sensitivity of SF 6 as a tracer of mesospheric air makes it an outlier in both the descent and mixing calculations. The inclusion of a small fraction of air from the mesosphere is necessary to bring the SF 6 mixing and descent calculations into agreement with the other tracers. The conclusions regarding descent and descent rates in the vortex are consistent with other modeling studies. The results indicate that mixing of midlatitude air into the winter vortex is not a significant contributor to the observed ozone changes in the 1999/2000 season.

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“…The data can be found on the internet at http://haloedata.larc.nasa.gov/. An unusually high peak of the WVMR was investigated in a sequence of articles [ Summers et al , 1996; Harries et al , 1996a, 1996b; Summers et al , 1997a, 1997b; Siskind and Summers , 1998; Summers and Siskind , 1999; Summers et al , 2001]. The effect is not a permanent phenomenon, but it occurs during certain seasons at different latitudes.…”

Section: Introductionmentioning

confidence: 99%

Autocatalytic water vapor production as a source of large mixing ratios within the middle to upper mesosphere

2005

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[1] Different measurements have shown that large water vapor mixing ratios occur in the upper mesosphere in high-latitude summer just under conditions of strongest solar insolation where photolysis should effectively reduce its value. The analysis of this finding by means of a high-resolution one-dimensional model supplies evidence that water vapor is autocatalytically formed below a crossover height of about 65 km and destroyed by photolysis above this altitude. We found three catalytic cycles of water vapor formation from the molecular hydrogen reservoir. Hydrogen radicals, resulting for the most part from water vapor by photolysis and oxidation by O( 1 D), act as catalysts. A great number of the hydrogen radicals return to water vapor, particularly under the condition of small atomic hydrogen concentration decreasing strongly with decreasing height. In the upper domain under the condition of large atomic hydrogen concentrations the formation of molecular hydrogen will be favored. Favorable conditions for large water vapor mixing ratios at high altitudes are given by an accelerated upward vertical wind. Below the crossover level the vertical wind should be weak so that H 2 and CH 4 have sufficient time to oxidize into H 2 O, a very slow process. Above this level, however, the vertical wind should be strong in order to lift the air, enriched with H 2 O, as quickly as possible to greater heights before the dissociation has an effective impact on the H 2 O distribution. Such accelerated upward vertical winds are typical of the mesosphere under certain seasonally latitudinal conditions. Calculations by means of our three-dimensional model COMMA-IAP yield seasonal-latitudinal patterns and variations approximately comparable with those of the HALOE observations. In the paper we discuss the chemical background and the interplay between dynamics and chemistry in more detail.Citation: Sonnemann, G. R., M. Grygalashvyly, and U. Berger (2005), Autocatalytic water vapor production as a source of large mixing ratios within the middle to upper mesosphere,

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On the distribution of mesospheric molecular hydrogen inferred from HALOE measurements of H₂O and CH₄

Cited by 30 publications

References 26 publications

Biogeochemical modelling of the rise in atmospheric oxygen

Biogeochemical modelling of the rise in atmospheric oxygen

Descent and mixing in the 1999–2000 northern polar vortex inferred from in situ tracer measurements

Autocatalytic water vapor production as a source of large mixing ratios within the middle to upper mesosphere

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On the distribution of mesospheric molecular hydrogen inferred from HALOE measurements of H2O and CH4

Cited by 30 publications

References 26 publications

Biogeochemical modelling of the rise in atmospheric oxygen

Biogeochemical modelling of the rise in atmospheric oxygen

Descent and mixing in the 1999–2000 northern polar vortex inferred from in situ tracer measurements

Autocatalytic water vapor production as a source of large mixing ratios within the middle to upper mesosphere

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On the distribution of mesospheric molecular hydrogen inferred from HALOE measurements of H₂O and CH₄