Effect of odd hydrogen on ozone depletion by chlorine reactions

Analysis of uncertainties in stratospheric perturbations requires the development of a model which uses a minimum of computer time yet is complete enough to represent reasonably the results of more complex models. Such a concise model has been developed and is described in this paper. The model is a steady state model using iteration to achieve coupling between interacting species. The species odd oxygen, H2O, H2, CO, N2O, odd nitrogen, CH4, CH3Cl, CCl4, CF2Cl2, CFCl3, and odd chlorine are determined from diffusion equations with appropriate sources and sinks. The HOx species, methane oxidation products, and relative species abundances within the odd oxygen, odd nitrogen, and odd chlorine families are solved in photochemical equilibrium, and N2, O2, CO2, and temperature have been assigned fixed profiles. Diurnal effects such as those due to chlorine nitrate formation are accounted for by analytic approximations. The model has been used to evaluate steady state perturbations due to injections of chlorine and NOx. The results are similar to those obtained by other models.

Section: Effects Of CLX and Nox Perturbationsmentioning

confidence: 89%

Uncertainty propagation in a stratospheric model 1. Development of a concise stratospheric model

Rundel¹,

Butler²,

Stolarski³

1978

“…The rate constants of reactions that interconvert water and odd hydrogen have been measured in the laboratory, and so, to an accuracy determined by uncertainty in the laboratory rate constants [Donahue et al, 1976], measurements of mesospheric water may be translated into mixing ratios of odd hydrogen. Rocket measurements of OH in the mesosphere [Anderson, 1971] are generally consistent with the laboratory rate constants and previous conceptions of mesospheric water content [Anderson and Donahue, 1975] and are also consistent with a 1.5 times larger water content.…”

Section: D•scusslonmentioning

confidence: 99%

Mesospheric water vapor measured from ground-based microwave observations

Radford¹,

Litvak²,

Gottlieb³

et al. 1977

An atmospheric emission line centered at 22,235 MHz has been detected repeatedly over the period of March-August 1975 with a radio telescope located at Westford, Massachusetts (42.5øN, 71.5øW). The line has also been detected in absorption against the sun's microwave continuum. From its exact coincidence in frequency with the well-known 1.3-cm line of the water molecule the line is identified with atmospheric water vapor. A mixing ratio distribution between altitudes of 50 and 80 km is derived from the measured line amplitude and shape. Mixing ratios as large as 15 ppm by volume, about 2 times larger than the maximum predicted by photochemical equilibrium calculations, are found at these mesospheric altitudes.

“…For O2 photolysis we follow Breig [1972], using two groups of solar fluxes: (1) solar flux data of Detwiler et al [1961] for the Schumann-Runge continuum and of Brinkmann et al [1966] for Schumann-Runge bands and the Herzberg continuum and (2) solar flux data of Parkinson and Reet)es [1969] for the Schumann-Runge continuum and bands and of Brinkmann et al [1966] for the H erzberg continuum.Group 1 gives about a factor of 3 higher O2 photolysis rate than group 2 at zero optical depth. We include also the uncertainties of the following key reaction rates[Liu and Donahue, 1974;Donahue et al, 1976]: Viewing geometry and counting rates observed during ozone absorption measurements on orbit 2. Temporary counting rate reductions due to guidance errors are indicated by arrows.…”

mentioning

confidence: 99%

Stellar occultation measurements of atmospheric ozone and chlorine from OAO 3

Riegler¹,

Drake²,

Liu³

et al. 1976

The Princeton University telescope on the Orbiting Astronomical Observatory 3 was used for occultation measurements of upper atmospheric species. The target star, β Cen, and observing date, July 26, 1975, were selected so that the line of sight grazed the earth's limb at local midnight. Observations at 2580, 2825, 2997, 3100, and 3428 Å produced ozone absorption data of high statistical accuracy between 48‐km and 114‐km tangent altitude. Near‐exponential density profiles are obtained up to 85 km. Near 100 km a significant density excess above the extrapolated low‐altitude profile is observed. Near‐equatorial observations at altitudes up to approximately 75 km agree well with theoretical calculations. Ozone densities measured at 6.5°–12.5°S above approximately 75 km exceed our theoretical calculations and are not understood at the present time. A search for the 1188‐Å chlorine line in the 1187‐Å O2 absorption feature was carried out at tangent altitudes of 96–116 km. An upper limit to the atomic chlorine mixing ratio at 106 km of 3 ppb is found. This upper limit exceeds the expected value for atomic chlorine by a factor of approximately 2.5.