Accretion is defined as the gradual collection of something over time. In

meteorology Meteorology is the scientific study of the Earth's atmosphere and short-term atmospheric phenomena (i.e. weather), with a focus on weather forecasting. It has applications in the military, aviation, energy production, transport, agricultur ...

atmospheric science Atmospheric science is the study of the Atmosphere of Earth, Earth's atmosphere and its various inner-working physical processes. Meteorology includes atmospheric chemistry and atmospheric physics with a major focus on weather forecasting. Clima ...

it is the process of accumulation of frozen water as precipitation over time as it descends through the atmosphere, in particular when an ice crystal or

snowflake A snowflake is a single ice crystal that is large enough to fall through the Earth's atmosphere as snow.Knight, C.; Knight, N. (1973). Snow crystals. Scientific American, vol. 228, no. 1, pp. 100–107.Hobbs, P.V. 1974. Ice Physics. Oxford: C ...

hits a

supercooled Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid below its freezing point without it becoming a solid. Per the established international definition, supercooling means ''‘cooling a substance be ...

liquid Liquid is a state of matter with a definite volume but no fixed shape. Liquids adapt to the shape of their container and are nearly incompressible, maintaining their volume even under pressure. The density of a liquid is usually close to th ...

droplet, which then freeze together, increasing the size of the water particle. The collection of these particles eventually forms

snow Snow consists of individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water througho ...

hail Hail is a form of solid Precipitation (meteorology), precipitation. It is distinct from ice pellets (American English "sleet"), though the two are often confused. It consists of balls or irregular lumps of ice, each of which is called a hailsto ...

in clouds and depending on lower atmosphere temperatures may become

rain Rain is a form of precipitation where water drop (liquid), droplets that have condensation, condensed from Water vapor#In Earth's atmosphere, atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is res ...

, sleet, or

graupel Graupel (; ), also called soft hail or hominy snow or granular snow or snow pellets, is precipitation that forms when supercooled water droplets in air are collected and freeze on falling snowflakes, forming balls of crisp, opaque rime. Gra ...

. Accretion is the basis for cloud formation and can also be seen as water accumulates on the

particulate matter Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspended in the air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate matter alone, though it is sometimes defin ...

and form jet contrails. This is because water vapor in the air requires condensation nuclei to form large droplets of solid or liquid water."Accretion (glossary definition)
. National Snow and Ice Data Center. Retrieved 16 January 2010.

References

Snow Snow or ice weather phenomena Water ice {{Meteorology-stub

See also

References