Composition of the Earth′s atmosphere 3.1.4



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3.1.4 Composition of the Earth′s atmosphere

The atmospheric composition data are abridged from US National Air and Space Administration (Washington, D.C.) model of the US standard atmosphere. This represents an idealised steady state from the surface up to 100 km relative to dry air at sea level.

(Parts in 10⁶ of dry air by volume)

N₂	O₂	Ar	CO₂	Ne	He	CH₄	Kr	N₂O	H₂	O₃	Xe
780 984	209 475	9340	314	18	5.2	2.0	1.14	0.5	0.5	0.4	0.086

The United Nations Environmental Programme (Data Report, 3rd edn, 1991–92) includes a collation for (at least) the period 1977–1989 of latitudinal differences in values of mean monthly concentrations of carbon dioxide, methane, nitrous oxide and fluorocarbons 11 and 12. Figure 1 (Parts 1, 2, 3 & 4) illustrates the 13-year rising trend in December levels of these four pollutants separately, for latitudes 71°N, 40°N, 19°N and 14°S and the South Pole.

Figure 2 portrays less clear cut trends, some first rising and then all falling, for sulphur dioxide mean concentrations in residential areas of 15 major cities of the world.

Figure 3 (Parts 1, 2, & 3) displays changes in anthropogenic emissions of carbon dioxide for 1970, 1980 and 1988, and of sulphur dioxide and oxides of nitrogen for 1980, 1984 and 1988, expressed in million tonnes per year and in proportion of the world total between continents. Data were abstracted and summarised by the UNEP from OECD reports and national statistics.

(Click the Images to view Larger Images) $CARBON DIOXIDE, as parts/million by mole fraction (ppmf),measured by non-dispersive IR analyser$ CARBON DIOXIDE, as parts/million by mole fraction (ppmf), measured by non-dispersive IR analyser Fig. 1 (Part 1)
METHANE, as parts/million by volume (ppmv), in dry air, measured by gc/fid Fig. 1 (Part 2)
$NITROUS OXIDE, as parts/million by mole fraction (ppmf),measured by gc/ecd$ NITROUS OXIDE, as parts/million by mole fraction (ppmf), measured by gc/ecd Fig. 1 (Part 3)
CFC11 (lower) & CFC12 (upper curve), as parts/million by volume (ppmv), measured by gc/ecd Fig. 1 (Part 4)
SULPUR DIOXIDE, as micrograms per cubic metre Fig. 2
Fig. 3 (Part 1)
Fig. 3 (Part 2)
Fig. 3 (Part 3)

G.F.Phillips

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