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Weather Glossary - K

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Katabatic wind

A local wind which develops due to cool, dense air flowing downhill. The cooler air is generally a result of night time radiational cooling in the lower layers of the atmosphere, but katabatic winds also occur over snow fields and glaciers. See also anabatic winds.

Katafront

A front where the warm air descends the frontal surface, except in the low layers.

Kelvin

Unit of thermodynamic temperature. Zero Kelvin is absolute zero (-273.15░C). Temperatures in Kelvin can be obtained from temperatures in Celsius by the formulae K=C+273.2.

Kelvin-Helmholtz billows

A phenomenon that occurs in a high-shear environment between two layers of fluid which are stably stratified (i.e. a denser fluid beneath a lighter fluid).

Kinetic energy

The energy a body possesses as a consequence of its motion. Defined as half the product of its mass and the square of its speed.

Knot

The unit of speed equal to 1 nautical mile/hour, or 1.85 km/h. The knot is commonly used to report wind speed and ocean current speed.

Knuckles

[Slang] Lumpy protrusions on the edges, and sometimes the underside, of a thunderstorm anvil. They usually appear on the upwind side of a back-sheared anvil, and indicate rapid expansion of the anvil due to the presence of a very strong updraft. They are not mammatus clouds. See also cumuliform anvil, anvil rollover.

K°ppen's classification of climates

Classification of climate based on annual and monthly means of temperature and precipitation which also takes into account the vegetation limits. It is a tool for presenting the world pattern of climate and for identifying important deviations from this pattern.

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