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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.

Køppen'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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