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Humid air is less dense than dry air because a molecule of water (m ≈ 18 Da) is less massive than either a molecule of nitrogen (m ≈ 28) or a molecule of oxygen (m ≈ 32). About 78% of the molecules in dry air are nitrogen (N 2). Another 21% of the molecules in dry air are oxygen (O 2). The final 1% of dry air is a mixture of other gases.
Since the saturation vapor pressure is proportional to temperature, cold air has a lower saturation point than warm air. The difference between these values is the basis for the formation of clouds. When saturated air cools, it can no longer contain the same amount of water vapor.
This is largely because air temperatures over land drop more in the winter than temperatures over the ocean. Water vapor condenses more rapidly in colder air. [50] As water vapor absorbs light in the visible spectral range, its absorption can be used in spectroscopic applications (such as DOAS) to determine the amount of water vapor in the ...
The amount of water vapor that can be stored in the air can be increased simply by increasing the temperature. [8] However, this can be a double edged sword as most condensation in the home occurs when warm, moisture heavy air comes into contact with a cool surface. As the air is cooled, it can no longer hold as much water vapor.
Atmospheric thermodynamics is the study of heat-to-work transformations (and their reverse) that take place in the Earth's atmosphere and manifest as weather or climate. . Atmospheric thermodynamics use the laws of classical thermodynamics, to describe and explain such phenomena as the properties of moist air, the formation of clouds, atmospheric convection, boundary layer meteorology, and ...
Fluid properties can also be observed in gases and even in particulate solids (such as sand, gravel, and larger objects during rock slides). A convection cell is most notable in the formation of clouds with its release and transportation of energy. As air moves along the ground it absorbs heat, loses density and moves up into the atmosphere.
Warm air has a lower density than cool air, so warm air rises within cooler air, [8] [better source needed] similar to hot air balloons. [citation needed] Clouds form as relatively warmer air carrying moisture rises within cooler air. As the moist air rises, it cools causing some of the water vapor in the rising packet of air to condense. [9]
Since colder air can hold less water vapor, moisture condenses to form clouds and precipitates as rain or snow on the mountain's upwind slopes. The change of state from vapor to liquid water releases latent heat energy which heats the air, partially countering the cooling that occurs as the air rises. The subsequent removal of moisture as ...