Atmospheric data mixing ratios

FIGURE 2,5 Atmospheric NiO mixing ratios over the last 250 years obtained from ice core data (Machida et al., 1995). Annual mean values at the South Pole for the period 1977 to 1991 are given by. squares. Solid curve is a fit to the data. 

Fig. 2.91 Relationship between cumulative anthropogenic CO2 emission (data from Boden 2009) and atmospheric CO2 mixing ratio (data from Fig. 2.70).

Due to the imbalance of sources and sinks, atmospheric N2O is increasing by 3 Tg N/yr or 0.2%/yr. Figure 12-9 shows average N2O mixing ratios from four stations in the NOAA-CMDL network, Barrow, Mauna Loa, Samoa, and the South Pole (data are from the NOAA-CMDL and can be obtained from www.cmdl.noaa.gov). The most recent IPCC estimate gives a total N2O source of 16 Tg N, 7 Tg of which are a result of human activities (IPCC, 1997). The largest contribution to the anthropogenic N2O sources is 3 Tg N from... 

Hellstrom et al (2004)] were used as a surrogate for atmospheric concentrations. They serve to evaluate the latitudinal gradients of the model results. The biomass DDT concentrations are compared to mixing ratios of DDT in the lowest atmospheric model layer. Ratios of observational data were calculated for pine needles from the same growth year. 

Other common ways of expressing abundances, particularly of solid or liquid particles, is to express them as concentrations in units of micrograms per cubic meter or nanomoles per cubic meter. For purposes of consistency, concentrations expressed in these units should be normalized to standard conditions of temperature and pressure. Because there is some confusion as to what constitutes standard conditions in atmospheric chemistry (273 K and 1.013 bar are commonly used in chemistry and physics and 293 K and 1.013 bar are used in engineering), it is important to define the standard conditions that are assumed when reporting data. This explicit definition is frequently not done. Concentrations expressed in these units can be easily converted to mixing ratios by use of the ideal gas law ... 

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. 

Fig. 1. The neutral composition of the Earth s atmosphere as a function of altitude. The sources of the altitudinal profile data are H, He, O, N2, 02, Ar, Ref.6) O3, Ref.7) H20, Refs. ) and10) NO, Refs.9) and 10) O 1 Ag), Ref.11) O below 90 km, Ref.12) CF2C12 and CFCI3, Ref.13) N20, Ref.14) H202, NO3 and N205, from model calculations given in Ref.ls) C02 is assumed to have a constant mixing ratio of 300 p.p.m. Clearly many other minority species are present in the lower atmosphere (e.g. OH, H02 see Ref.15)) but these have been omitted for clarity.

Migeotte and Neven (175) first observed atmospheric CO and found a mixing ratio of 0.2 to 0.3 ppm. In other data summarized by Junge (128), the mixing ratio in the troposphere had a range of 0.1 to 0.2 ppm. 

The measurements of H2 mixing ratios in the atmosphere, the troposphere, and the lower stratosphere were carried out by Schmidt in 1974. A constant mixing ratio of 0.548 ppmv was found in the southern troposphere and in the lower stratosphere ofthe northern hemisphere. Higher levels of 0.558 and 0.585 ppmv were obtained in the northern hemisphere in the upper troposphere and in surface air, respectively. The data do not indicate any change in the H2 mixing ratio of the lower stratosphere up to 4 km above the tropopause. The almost constant H2 mixing ratio in the tropopause region indicates that the flux of H2 between the troposphere and the stratosphere is very small. 

The observed noble-gas abundances and isotopic ratios on Venus are summarized in Tables 3 and 4. The helium mixing ratio is a model-dependent extrapolation of the value measured in Venus upper atmosphere, where diffusive separation of gases occurs. The main differences between Venus and Earth are that Venus is apparently richer in He, Ar, and Kr than the Earth, and the low " Ar/ Ar ratio of — 1.1 on Venus, which is —270 times smaller than on Earth. The low " Ar/ Ar ratio may reflect more efficient solar-wind implantation of Ar in solid grains accreted by Venus and/or efficient early outgassing that then stopped due to the lack of plate tectonics. Wieler (2002) discusses the noble-gas data. Volkov and Frenkel (1993) and Kaula (1999) describe implications of the " Ar/ Ar ratio for outgassing of Venus. 

The measured " °Ar/ Ar ratio is 1.11 0.02, substantially less radiogenic than the terrestrial atmosphere. For a mixing ratio of 21-48 ppm (Donahue and Pollack, 1983), the atmosphere contains (1.8-4.4) X 10" atoms " °Ar. Divided by the mass of the planet, this corresponds to (3.6-9.0) X 10 atoms " °Ar g This is 0.2-0.5 times the value for the Earth. However, Venus appears to be deficient in potassium. Data for the K/U ratio of the surface indicate that K/U = 7,220 1,220 (Kaula, 1999), or 0.57 0.10 times that of the value of 1.27 X 10" commonly taken for the Earth. Assuming that Venus has the same uranium concentration as the total Earth (including the core) of 14 ppb, then 12-28% of the " °Ar produced in Venus is now in the atmosphere (see Kaula, 1999). This indicates that a substantial inventory of " °Ar remains within the planet, possibly also accompanied by up to an equivalent... 

Figure 16 Relationship between change in A(A C) of vascular land plants determined experimentally in response to growth under different O2/CO2 atmospheric mixing ratios. A(A C) is the change in carbon isotope fractionation relative to fractionation for the controls at present day conditions (21% O2, 0.036% CO2). The solid line shows the nonlinear curve fitted to the data, given by A(A C) = - 19.94 -h 3.195 X InfOz/COz) ( ) Phaseolus vulgaris, ( ) Sinapis alba, ( ) from Berner et al. (2000) (-I-) from Berry et al. (1972) (Beerling et al., 2002) (reproduced by permission of Elsevier from Geochem. Cosmochim. Acta 2002, 66, 3757-3767).

Clark (55) reviewed the laboratory data and concluded that there was no homogeneous gas phase process capable of accounting for the CO and O2 mixing ratio limits at any altitude. More recently, McElroy and McConnell (93) have concluded that vertical transport with high eddy diffusion coefficients may explain the mixing ratios in the Mars upper atmosphere. The same mechanism cannot, however, account for the lower atmosphere. 

FIGURE 4-43 Increase in the mixing ratio of carbon dioxide in Earth s atmosphere as measured since March 1958 at the Mauna Loa Observatory (data from Keeling and Whorf, 1998). 

Fig. 1-2. Secular rise of C02 mixing ratios in the atmosphere. Dots represent monthly mean values in ppmv as observed with a continuously recording nondispersive infrared analyzer. The smooth curve represents a fit of data to a fourth harmonic annual cycle, which increases linearly with time, and a spline fit of the interannual component of variation. Top Mauna Loa Observatory, Hawaii bottom South Pole. [From C. D. Keeling el al. (1982) and unpublished data courtesy C. D. Keeling.]...

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