Troposphere mixing ratio

Carbon Monoxide. Methods for determining carbon monoxide include detection by conversion to mercury vapor, gas filter correlation spectrometry, TDLAS, and grab sampling followed by gas chromatograph (GC) analysis. The quantitative liberation of mercury vapor from mercury oxide by CO has been used to measure CO (73). The mercury vapor concentration is then measured by flameless atomic absorption spectrometry. A detection limit of 0.1 ppbv was reported for a 30-s response time. Accuracy was reported to be 3% at tropospheric mixing ratios. A commercial instrument providing similar performance is available. 

Because of this growth, which is observed in the abundance of other halocarbons as well, "average" reference profiles as required for model atmospheres can only be determined for a specified time [24], Likewise, averaging over a time span of several years is not appropriate when absolute numbers of the mixing ratios are taken. We have, therefore, calculated relative abundances for every individual balloon profile with respect to tropospheric mixing ratios as measured at the same time. This use of relative data with respective tropospheric mixing ratios fixed at 100% has another advantage, as it eliminates the errors related to the absolute calibration. 

The hydrohalocarbons shown in fig. 11 differ quite considerably with respect to their decomposition in the stratosphere, predominantly by OH attack. While CH3C1 is depleted to less than 10% of its tropospheric mixing ratio below 30 km., CHC1F2 is relatively stable at higher altitudes. This is due to the temperature dependence of its reaction... 

Figure 14 Latitude-altitude cross-section of CFC-12 in the northern hemisphewHorelative units with respect to the tropospheric mixing ratios fixed at 100%. Average results obtained by l loon measurements at 17,5°N, 44°N, and 69°N are combined with data of project AIRSTREAM (Leifer, 1992) averaged at every 10 latitude interval. The mean tropopause is the average taken from all AIRSTREAM flights irrespective of the season.

Dhar and Ram (50) found formaldehyde in rain water and estimated a tropospheric mixing ratio of 0.7 ppb, while Cauer (36) measured a mean value of 0.4 ppb. Lodge and Pate (160) obtained an average value of 1.1 ppb for the total aliphatic aldehydes in surface air in the tropics. Levy (152) proposed the formation of formaldehyde via the tropospheric oxidation of methane and calculated (155) an upper limit of 1 ppb for the mixing ratio, with an altitude profile for a summer midlatitude decreasing from 0.6 ppb at the ground to less than 0.01 ppb in the upper troposphere, where methane oxidation is very slow (154). 

Within the steady-state approximation, the total column loss rate for CH and the total column production and loss rates for CO [Wofsy et al. (256) and Levy (155)] and for H2 [Levy (155)] have been calculated. The resulting residence times and tropospheric mixing ratios are in harmony with recent experimental results, with the exception of the n(C0) mixing ratio. This ratio is... 

One may conclude that approximately 600 Tg of methane are produced each year. Since the total atmospheric burden of methane is about 4900 Tg (corresponding to a mean tropospheric mixing ratio of about 1.75 ppmv), a global atmospheric lifetime of 8 years can be derived. 

Table 4-6. Recent Measurements of the Average Tropospheric Mixing Ratio m of Methane and the Ratio m /msfor the Mixing Ratios in the Northern and Southern Hemispheres...

Both reactions are exothermic. In this manner, H2S would be reconstituted and its lifetime raised to a value greater than that given in Table 10-2. Since, however, the tropospheric mixing ratios of HCHO and H202 are smaller... 

Carbonyl sulfide is the most abundant sulfur gas in the global background atmosphere because of its low reactivity in the troposphere and its correspondingly long residence time. It is the only sulfur compound that survives to enter the stratosphere. (An exception is the direct injection of SO2 into the stratosphere in volcanic eruptions.) In fact, the input of OCS into the stratosphere is considered to be responsible for the maintenance of the normal stratospheric sulfate aerosol layer. Measurements of atmospheric OCS mixing ratios and surface fluxes have been reviewed by Chin and Davis (1995). OCS exhibits an average tropospheric mixing ratio of about 500 ppt. 

It can be assumed that these masses divide equally between the NH and SH. With the average molecular weight of air, = 28.9 g moPthe tropospheric mass of a substance of molecular weight M that has a tropospheric mixing ratio of is... 

Barkley et al. (2008) found globally tropospheric and stratospheric means to be 433 ppt and 330 ppt, slightly lower than previous measurements of free tropospheric mixing ratio of 480-520 ppt (Notholt et al. 2003) and stratospheric mixing... 

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