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The density of air at sea level is about 1.2 kg/m 3 (1.2 g/L, 0.0012 g/cm 3). Density is not measured directly but is calculated from measurements of temperature, pressure and humidity using the equation of state for air (a form of the ideal gas law). Atmospheric density decreases as the altitude increases.
At 101.325 kPa (abs) and 15 °C (59 °F), air has a density of approximately 1.225 kg/m 3 (0.0765 lb/cu ft), which is about 1⁄800 that of water, according to the International Standard Atmosphere (ISA). [citation needed] Pure liquid water is 1,000 kg/m 3 (62 lb/cu ft).
The large impedance contrast between air and water (the ratio is about 3600) and the scale of surface roughness means that the sea surface behaves as an almost perfect reflector of sound at frequencies below 1 kHz. Sound speed in water exceeds that in air by a factor of 4.4 and the density ratio is about 820.
In meteorology, an air mass is a volume of air defined by its temperature and humidity. Air masses cover many hundreds or thousands of square miles, and adapt to the characteristics of the surface below them. They are classified according to latitude and their continental or maritime source regions. Colder air masses are termed polar or arctic ...
Because water is much more dense than air, the displacement of water by air from a surface gravity wave feels nearly the full force of gravity (′). The displacement of the thermocline of a lake, which separates warmer surface from cooler deep water, feels the buoyancy force expressed through the reduced gravity. For example, the density ...
(The total air mass below a certain altitude is calculated by integrating over the density function.) For the ocean example there was a sharp transition in density at the top or "surface" of the ocean. However, for atmospheres made of gas there is no equivalent sharp transition or edge.
The mixed layer plays an important role in the physical climate. Because the specific heat of ocean water is much larger than that of air, the top 2.5 m of the ocean holds as much heat as the entire atmosphere above it. Thus the heat required to change a mixed layer of 2.5 m by 1 °C would be sufficient to raise the temperature of the ...
Venus's atmosphere is composed of 96.5% carbon dioxide and 3.5% nitrogen, with other chemical compounds present only in trace amounts. [1] It is much denser and hotter than that of Earth; the temperature at the surface is 740 K (467 °C, 872 °F), and the pressure is 93 bar (1,350 psi), roughly the pressure found 900 m (3,000 ft) under water on ...