Ice nucleus
Encyclopedia
An ice nucleus is a particle which acts as the nucleus
for the formation of an ice crystal in the atmosphere
.
The presence of ice nuclei increase the temperature that ice
will form in the atmosphere from around −42°C to about −10°C. There are many processes that can take place in the atmosphere to form ice particles, the simplest is by water vapor depositing
directly onto the solid particle. The presence of an ice nucleus can also cause a previously supercooled
water droplet to freeze
through contact, immersion or dissolution within the water that would otherwise have stayed in the liquid phase at a given temperature.
Ice particles can have a significant effect on cloud
dynamics. They are known to be important in the processes by which clouds can become electrified, which causes lightning
. They are also known to be able to form the seeds for rain droplets
.
Many different types of particulates
in the atmosphere can act as ice nuclei, both natural and anthropogenic, including those composed of minerals, soot, organic matter and sulfate. However, the exact nucleation
potential of each type varies greatly, depending on the exact atmospheric conditions. Very little is known about the spatial distribution of these particles, their overall importance on global climate through ice cloud formation and whether human activity has played a major role in changing these effects.
Recent research shows that bacteria found in the atmosphere all over the world may be responsible for much ice nucleation.
Nucleation
Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...
for the formation of an ice crystal in the atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
.
The presence of ice nuclei increase the temperature that ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
will form in the atmosphere from around −42°C to about −10°C. There are many processes that can take place in the atmosphere to form ice particles, the simplest is by water vapor depositing
Deposition (physics)
Deposition is a process in which gas transforms into solid . The reverse of deposition is sublimation.One example of deposition is the process by which, in sub-freezing air, water vapor changes directly to ice without first becoming a liquid...
directly onto the solid particle. The presence of an ice nucleus can also cause a previously supercooled
Supercooling
Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid....
water droplet to freeze
Freezing
Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....
through contact, immersion or dissolution within the water that would otherwise have stayed in the liquid phase at a given temperature.
Ice particles can have a significant effect on cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
dynamics. They are known to be important in the processes by which clouds can become electrified, which causes lightning
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...
. They are also known to be able to form the seeds for rain droplets
Cloud seeding
Cloud seeding, a form of intentional weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud...
.
Many different types of particulates
Particulates
Particulates – also known as particulate matter , suspended particulate matter , fine particles, and soot – are tiny subdivisions of solid matter suspended in a gas or liquid. In contrast, aerosol refers to particles and/or liquid droplets and the gas together. Sources of particulate matter can be...
in the atmosphere can act as ice nuclei, both natural and anthropogenic, including those composed of minerals, soot, organic matter and sulfate. However, the exact nucleation
Nucleation
Nucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...
potential of each type varies greatly, depending on the exact atmospheric conditions. Very little is known about the spatial distribution of these particles, their overall importance on global climate through ice cloud formation and whether human activity has played a major role in changing these effects.
Recent research shows that bacteria found in the atmosphere all over the world may be responsible for much ice nucleation.
See also
- Bergeron processBergeron processThe Bergeron–Findeisen process , also known as the cold rain or ice crystal process, is the formation of precipitation in the cold clouds of the mid and upper latitudes by ice crystal growth. The equilibrium vapor pressure over water is greater than the saturation vapor pressure over ice, at the...
- Cloud condensation nucleiCloud condensation nucleiCloud condensation nuclei or CCNs are small particles typically 0.2 µm, or 1/100 th the size of a cloud droplet ) about which cloud droplets coalesce. Water requires a non-gaseous surface to make the transition from a vapour to a liquid. In the atmosphere, this surface presents itself as tiny...
- NucleationNucleationNucleation is the extremely localized budding of a distinct thermodynamic phase. Some examples of phases that may form by way of nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation...
- SnowSnowSnow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
- SupercoolingSupercoolingSupercooling, also known as undercooling, is the process of lowering the temperature of a liquid or a gas below its freezing point without it becoming a solid....