I. Atmosphere
A. Air vs. Atmosphere
B. Atmosphere - global average
- composition
- natural gases- clean, dry air (Table 1-2; Fig. 1-12)
- N (nitrogen)- 78%
- O (oxygen)- 21%
- Ar (argon)1%
- CO2 (carbon dioxide)
- O3 (ozone; varies vertically)
- CH4 & N2O (methane and nitrogen oxides)
- H2O vapor
- pollutants
- human component
- aerosols
- dust
- salt
- volcanic ash
- water droplets and ice particles
- Pressure and density (fig. 1-20)
- air is compressed by the weight of overlying air,
- air at bottom is tightly compressed
- 50% of atmosphere is in lowest 5.6km (18,000 ft)
- 90% of atmosphere is in lowest 16km (10 miles)
- lower atmosphere - high density (decreases with elevation)
- lower atmosphere - high pressure (decreases with elevation)
sea level - 14.7psi = 1013.25mb = 29.92 in Hg
- Temperature
- Temperature decreases with increasing elevation near Earth's surface
- normal environmental lapse rate - 6.5° C/km or 3.5° F/1000ft
- layers (fig. 1-22) - defined by temperature gradient
- troposphere (~12km)
- weather
- T decreases with altitude
- most of the dust and H2O
- tropopause
- stratosphere (50km)
- T increase with altitude (inversion)
- ozone layer (25km)
- mesosphere (80km)
- T decrease
- pressure down to 1 mb
- above 99.9% of the atmosphere
- thermosphere (ionosphere)
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