National Weather Service Glossary
This glossary contains information on more than 2000 terms, phrases and abbreviations used by the NWS. Many of these terms and abbreviations are used by NWS forecasters to communicate between each other and have been in use for many years and before many NWS products were directly available to the public. It is the purpose of this glossary to aid the general public in better understanding NWS products.
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Here are the results for the letter K
- Smoke- Smoke in various concentrations can cause significant problems for people with respiratory ailments. It becomes a more universal hazard when visibilities are reduced to Â¼ mile or less.
- K AMS
- Cold Air Mass
- K Corona
- In solar-terrestrial terms, of the white-light corona (that is, the corona seen by the eye at a total solar eclipse), that portion which is caused by sunlight scattered by electrons in the hot outer atmosphere of the sun.
- A measure of the thunderstorm potential based on vertical temperature lapse rate, moisture content of the lower atmosphere, and the vertical extent of the moist layer. The temperature difference between 850 mb and 500 mb is used to parameterize the vertical temperature lapse rate. The 850 dew point provides information on the moisture content of the lower atmosphere. The vertical extent of the moist layer is represented by the difference of the 700 mb temperature and 700 mb dew point. This is called the 700 mb temperature-dew point depression. The index is derived arithmetically and does not require a plotted sounding.
K-index = (850 mb temperature - 500 mb temperature) + 850 mb dew point - 700 mb dew point depression
- Katabatic Wind
- A wind that is created by air flowing downhill.
- A front where the warm air descends the frontal surface (except in the low layers of the atmosphere).
- Keetch-Byrum Drought Index
- An index used to gage the severity of drought in deep duff and organic soils.
- Kelvin Temperature Scale
- An absolute temperature scale in which a change of 1 Kelvin equals a change of 1 degree Celsius; 0ÂºK is the lowest temperature on the Kelvin scale. The freezing point of water is +273ÂºK (Kelvin) and the boiling point of +373ÂºK. It is used primarily for scientific purposes. It is also known as the Absolute Temperature Scale.
- Kelvin Waves
- Fluctuations in wind speed at the ocean surface at the Equator result in eastward propagating waves, known as Kelvin Waves. Kelvin Waves cause variations in the depth of the oceanic thermocline, the boundary between warm waters in the upper ocean and cold waters in the deep ocean. They play an important role in monitoring and predicting El NiÃ±o episodes.
- Kelvin-Helmholtz Waves
- Vertical waves in the air associated with wind shear across statically-stable regions. Can appear as breaking waves and as braided patterns in radar images and cloud photos.
- The internationally recognized unit used by the Atmospheric Environment Service for measuring atmospheric pressure. Abbreviated kPa.
- Kinetic Energy
- Energy that a body has as a result of its motion. Mathematically, it is defined as one-half the product of a body's mass and the square of its speed (KE = 1/2 * mass * velocity squared).
- An electron tube used as a low-power oscillator or a high-power amplifier at ultrahigh frequencies.
- (abbrev. Kt) Unit of speed used in navigation, equal to 1 nautical mile (the length of 1 minute latitude) per hour or about 1.15 statute miles per hour, or 0.5 meters/sec).
- Slang for 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 and anvil rollover.
- Kp Index
- A 3-hourly planetary geomagnetic index of activity generated in Gottingen, Germany, based on the K Index from 12 or 13 stations distributed around the world
- (Knot)- Unit of speed used in navigation, equal to 1 nautical mile (the length of 1 minute latitude) per hour or about 1.15 statue miles per hour, or 0.5 meters/sec).