In Meteorology, What Is Saturation?
Wet air with a water vapor pressure greater than the saturated water vapor pressure at the same temperature and pressure.
- Chinese name
- Supersaturated air
- Foreign name
- super-saturated air
- Related terms
- Saturated air
- Subject branch
- Atmospheric Science
- Wet air with a water vapor pressure greater than the saturated water vapor pressure at the same temperature and pressure.
Supersaturated air description
- In terms of meteorology, supersaturation refers to a state where the water vapor content exceeds the saturation value relative to pure water or pure ice, that is, the relative humidity is greater than 100%. In the laboratory, pure wet air without impurities can be cooled to a temperature of 300% supersaturation without condensation. Because condensation of water vapor requires nodules, and embryos in liquid water need to form in pure water, a certain degree of supersaturation must be achieved to overcome the free energy on the surface of the water droplet embryo. In the actual atmosphere, there are abundant condensed nodules, and only a small degree of supersaturation is required to form a water droplet embryo [1] .
Supersaturated air
- There are many parameters that characterize air humidity, and relative humidity is one of the commonly used constants. Relative humidity is the ratio of the molar fraction of water vapor to saturated water vapor. Its value shows how high the air is saturated. Air with a relative humidity of 100% is saturated air, and greater than 100% is supersaturated air. Supersaturation is the difference between relative humidity and 100%. The formula is
- Where s is supersaturation and f is relative humidity. During the formation of natural clouds, the supersaturation is generally several thousandths to several percents.
Supersaturated in a cloud of supersaturated air
- The existence of cloud particles requires a saturated humidity condition relative to the surface of the cloud particles. Generally, the relative humidity in the cloud is about 100%. Figure 1 shows the distribution of the relative frequency of the relative humidity in the medium and small scale cumulus clouds with the relative humidity calculated from the observation results of the vertical velocity and cloud drop scale. Not saturated. The median relative humidity in the cloud is about 100.1%, while the relative humidity in the center of the convective cloud body can reach 107%, showing that most of the cloud is in a supersaturated state.
- Figure 1 Distribution of cumulative relative humidity with relative humidity
- Figure 1 Distribution of cumulative relative humidity with relative humidity in medium- and small-scale cumulus clouds [2] (curve a is the observation result within the cloud area 300 meters from the cloud base; curve b is the observation result of the entire cloud body)