Hydrogen mixing ratio, vertical distribution

Fig. 8. Vertical distribution of molecular oxygen (Oj) mixing ratio in prebiological paleo-atmosphere. Calculations for molecular hydrogen (Hj) = 17 ppmv, carbon dioxide (CO2) = 280 ppmv, and three different solar ultraviolet fluxes.

The vertical distributions of methane and hydrogen in the stratosphere are shown in Fig. 3-10. The loss of methane is made evident from the decrease of the CH4 mixing ratio with increasing altitude. In the lower stratosphere, reaction with OH is the sole loss process. In the upper stratosphere it is supplemented by reactions of methane with O( D) and Cl atoms. Crutzen and Schmailzl (1983) estimated from two-dimensional model calculations that OH and 0( D) + C1, respectively, contribute about 50% each to the total loss of methane. The global rate of stratospheric CH4 removal according to their estimate is 42 Tg/yr. In Section 4.3 a different method will be employed to derive a value of 55 Tg CH4/yr. 

Vertical distributions of the molecular density and mixing ratios of H2O and HDO in the Venus mesosphere were measured by Fedorova et al., 2008 [129]. The experiment was carried out on board of Venus express mission (SOIR instrument, 2.32-4.35 pm). The atmosphere was sounded during solar occultation in the range of altitudes from 65 to 130 km. An enrichment of D to hydrogen indicates the escape of water from Venus. Bertaux et al., 2007 [25] report on the detection of a warm layer at 90-120 km. ... 

---