Methane Mixing Ratio Research Articles

Climatic factors on the Archean earth

There is no strong evidence for extreme climates during the Archean. Galciogenics rokcs are rare, while evaporites are about as widespread as in later geological periods. Sedimentary rocks suggest processes of erosion and weathering not particularly anomalous. This findings is surprising in the light of simple physical reasons to believe that the sun was less bright. Although the area of exposed land was probably low, the albedo change associated with more extensive oceans could hardly have been large enough to prevent glaciation. A stronger atmospheric greenhouse is indicated. Carbon dioxide was the most likely candidate gas. A variety of arguments suggest that it was much more abundant. Methane is another possible contributor to the greenhouse. While abiotic sources of this gas were probably negligible then as now, biogenic sources could have sustained methane mixing ratios in the range 10 −4 to 10 −6. Other climatic factors of uncertain impact include more rapid rotation of the earth — the lenght of the day was probably about fifteen hours throughout most of Archean time - and little or no continental land areas, which would have reduced the importance of landsea circulations while permitting less restricted zonal flow of ocean currents.

The upper atmosphere of Uranus - Mean temperature and temperature variations

The number-density, pressure, and temperature profiles of the Uranian atmosphere in the pressure interval from 0.3 to 30 dynes/sq cm are derived from observations of the occultation of SAO 158687 by Uranus on 1977 March 10, observations made from the Kuiper Airborne Observatory and the Cape Town station of the South African Astronomical Observatory. The mean temperature is found to be about 95 K, but peak-to-peak variations from 10 K to 20 K or more exist on a scale of 150 km or 3 scale heights. The existence of a thermal inversion is established, but the inversion is much weaker than the analogous inversion on Neptune. The mean temperature can be explained by solar heating in the 3.3 micron methane band with a methane mixing ratio of 4 x 10 to the -6th combined with the cooling effect of ethane with a mixing ratio of not greater than 4 x 10 to the -6th. The temperature variations are probably due to a photochemical process that has formed a Chapman layer.

Vertical profiles of CO & CH4 in the lower and middle troposphere over the eastern United States January 1978

Samples of tropospheric air were obtained over the Eastern United States during January of 1978. These samples were analyzed by means of gas chromatography using flame ionization detection to produce vertical profiles of carbon monoxide and methane from the surface to 8 km. The carbon monoxide mixing ratios at 35°N and 45°N agree with previously published values; however, the mixing ratio at 25°N was significantly lower than most previously published values. The methane mixing ratio was found to be weakly dependent on latitude and to have an average value of 1.64 ppm.

Methane band limb-brightening on Uranus

Area scanner measurements of the brightness distributions of Uranus at 6300 and 7250 Å are presented. At the former wavelength, which is characteristic of continuum radiation, the observed limb-darkening is consistent with the results of Stratoscope observations. At the latter wavelength, in the center of a strong methane absorption band, the planet shows substantial limb-brightening as has been reported by other investigators. The limb-brightening and geometric albedo of Uranus in this methane band can be explained in terms of a clear atmospheric model in which the methane partial pressure above the saturation level is equal to its equilibrium vapor pressure. This conclusion is relatively insensitive to the methane mixing ratio below the saturation level. The presence of a high-altitude, conservatively, isotropically scattering haze of optical thickness 0.1, such as that previously proposed as a possible cause of the 7250-Å limb-brightening, would produce a geometric albedo at this wavelength that is substantially larger than the value observed for Uranus.

A model for the temperature inversion within the atmosphere of Saturn

A model for the temperature inversion within the atmosphere of Saturn is proposed and is shown to be consistent with photometric data in the 17- to 25-μm region. The proposed model incorporates solar heating by some “aerosol,” with the aerosol heating per unit mass of the atmosphere being uniformly distributed throughout that portion of the atmosphere overlying the upper cloud deck. For a methane-to-hydrogen mixing ratio of 7 × 10 −4, the model results suggest that 20% of the incident solar radiation is absorbed by the aerosol, while this is reduced to 16% for an enhanced methane mixing ratio of 2.1 × 10 −3.

Recovery of the mean Jovian temperature structure from inversion of spectrally resolved thermal radiance data

Abstract The mean thermal structure of the Jovian atmosphere near the temperature minimum (0.1 bar) is recovered by inversion of thermal radiance data. Improvements over previous studies of this type are made in two respects. (1) Care is taken to select data sources which are on a consistent calibration scale and from a frequency region which minimizes the variance in the recovered temperature. (2) The accuracy in the temperature recovery vs the vertical resolution capability is studied quantitatively. The contributions of various sources of systematic error, which generate significant uncertainty in the recovered thermal structure, are assessed. Sources of systematic error include assumptions about the stratospheric NLTE source function, the extent of cloud cover, the methane mixing ratio, and the calibration scale. Future investigations are outlined which would reduce such uncertainties and provide consistency with a wider range of data on the Jovian upper atmosphere.

The occulation of β Scorpii by Jupiter. IV. Diurnal temperature variations and the methane mixing ratio in the Jovian upper atmosphere

The nightime cooling of the Jovian atmosphere near the occulation level of 10 14cm −3 is calculated using the models of Strobel (1973) and Strobel and Smith (1973). The amount of cooling is found to depend on χ, the methane mixing ratio; μ the mean molecular weight; and the sunrise temperature. Using the range of sunrise (emersion) temperatures observed by Veverka et al. (1974) , the overnight cooling is calculated to be 1.5–5.5°K, if reasonable assumptions are made for χ and μ. The argument may be reversed to show that the agreement in measured sunrise and sunset temperatures obtained by other observers of the β Sco occulation implies that χ cannot be significantly greater than the generally accepted value of 7 ×10 −4.

Détermination de la distribution verticale du méthane stratosphérique par spectrométrie infrarouge en ballon

Solar spectra recorded by means of a balloon borne spectrometer over the 3 to 4 /im wavelength range at solar zenith angles between 75° and 95° from an altitude of 34 km are presented. The mixing ratio of methane between 16 and 33 km which is deduced from the measurements decreases in the stratosphere. These observational results confirm the conclusion drawn from sampling experiments made by Bainbridge and Heidt up to 23 km and show that the mixing ratio decreases by a factor of about 3 between the tropopause at 13.5 km and the altitude of 33 km in the stratosphere.

Upper limit of hydrogen and helium concentrations on Titan

The satellite Titan is commonly quoted as possessing an atmosphere consisting of at least 2 × 104 cm atm of methane. Plausible additional atmospheric constituents like hydrogen and helium are assumed to have completely escaped from the satellite. However, the employment of recent techniques to the upper atmosphere of Titan permits an improved estimate of the upper limits of the hydrogen to methane and helium to methane mixing ratios existing in the lower atmosphere of Titan, namely 10−6±1 and 10−3.5±0.5.

Atmospheric Composition of the Jovian Planets

Abstract Models for line formation in the atmospheres of the outer planets are discussed critically. It is shown that Jupiter's cloud deck cannot he regarded as a simple reflecting surface and that scattering processes must be involved to some extent in the detailed mechanism of line formation. The theory of line formation in a homogeneous, semi-infinite, isotropically scattering atmosphere is reviewed from an intuitive viewpoint, and it is shown that qualitatively this theory can account for much of the observed morphological behavior of absorption lines in the atmospheres of Jupiter and Saturn. Uranus and Neptune possess very deep hydrogen atmospheres and Rayleigh scattering plays a role in line formation for these planets. Molecular hydrogen is the most abundant constituent in Jupiter's atmosphere. The mixing ratio of helium is less than 0.5, as deduced from analysis of line widths of a weak methane band by Owen. The mixing ratio of methane is of the order 5×1−4 and, in the region of the atmosphere pro...

Pharmaceutical Centers

Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92 (11), 14987–15001) presented a range of temperature and methane profiles for Uranus that were consistent with 1986 Voyager radio occultation measurements of refractivity versus altitude. A localized refractivity slope variation near 1.2 bars was interpreted to be the result of a condensed methane cloud layer. However, models fit to near-IR spectra found particle concentrations much deeper in the atmosphere, in the 1.5–3 bar range (Sromovsky, L.A., Irwin, P.G.J., Fry, P.M. [2006]. Icarus 182, 577–593; Sromovsky, L.A., Fry, P.M. [2010]. Icarus 210, 211–229; Irwin, P.G.J., Teanby, N.A., Davis, G.R. [2010]. Icarus 208, 913–926), and a recent analysis of STIS spectra argued for a model in which aerosol particles formed diffusely distributed hazes, with no compact condensation layer (Karkoschka, E., Tomasko, M. [2009]. Icarus 202, 287–309). To try to reconcile these results, we reanalyzed the occultation observations with the He volume mixing ratio reduced from 0.15 to 0.116, which is near the edge of the 0.033 uncertainty range given by Conrath et al. (Conrath, B., Hanel, R., Gautier, D., Marten, A., Lindal, G. [1987]. J. Geophys. Res. 92 (11), 15003–15010). This allowed us to obtain saturated mixing ratios within the putative cloud layer and to reach above-cloud and deep methane mixing ratios compatible with STIS spectral constraints. Using a 5-layer vertical aerosol model with two compact cloud layers in the 1–3 bar region, we find that the best fit pressure for the upper compact layer is virtually identical to the pressure range inferred from the occultation analysis for a methane mixing ratio near 4% at 5°S. This strongly argues that Uranus does indeed have a compact methane cloud layer. In addition, our cloud model can fit the latitudinal variations in spectra between 30°S and 20°N, using the same profiles of temperature and methane mixing ratio. But closer to the pole, the model fails to provide accurate fits without introducing an increasingly strong upper tropospheric depletion of methane at increased latitudes, in rough agreement with the trend identified by Karkoschka and Tomasko (Karkoschka, E., Tomasko, M. [2009]. Icarus 202, 287–309).