A shortwave or shortwave trough is an embedded kink in the

trough Trough may refer to: In science * Trough (geology), a long depression less steep than a trench * Trough (meteorology), an elongated region of low atmospheric pressure * Trough (physics), the lowest point on a wave * Trough level (medicine), the l ...

ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...

pattern. Its length scale is much smaller than that of and is embedded within longwaves, which are responsible for the largest scale (

synoptic scale The synoptic scale in meteorology (also known as large scale or cyclonic scale) is a horizontal length scale of the order of 1000 kilometers (about 620 miles) or more. This corresponds to a horizontal scale typical of mid-latitude depressions (e. ...

) weather systems. Shortwaves may be contained within or found ahead of longwaves and range from the mesoscale to the synoptic scale. Shortwaves are most frequently caused by either a cold pool or an upper level

front Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music * The Front (band), an American rock band signed to Columbia Records and active in the 1980s and e ...

. Shortwaves are commonly referred to as a vorticity maximum.

Corresponding weather and effects

Shortwaves are often associated with warm air advection (WAA) or cold air

advection In the field of physics, engineering, and earth sciences, advection is the transport of a substance or quantity by bulk motion of a fluid. The properties of that substance are carried with it. Generally the majority of the advected substance is al ...

(CAA), which influence temperature. Due to the way they move the air around them and the way air moves away from them, shortwaves produce positive curvature

vorticity In continuum mechanics, vorticity is a pseudovector field that describes the local spinning motion of a continuum near some point (the tendency of something to rotate), as would be seen by an observer located at that point and traveling along wit ...

and positive shear vorticity, respectively. Ahead of a shortwave there is large-scale lift due to divergence from

positive vorticity advection Positive vorticity advection, or PVA, is the result of more cyclonic values of vorticity advecting into lower values of vorticity. It is more generally referred to as "Cyclonic Vorticity Advection" (CVA). In the Northern Hemisphere this is positive ...

(PVA). This lift often causes

precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzle, rain, sleet, snow, ice pellets, graupel and hail. ...

. In a capped environment, the lift generated by a shortwave may cool the inversion layer as a result of the rapid expansion of the air (

adiabatic cooling In thermodynamics, an adiabatic process (Greek: ''adiábatos'', "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, a ...

), allowing for deep, moist

convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the convec ...

Convective Development

Shortwave troughs are a cause of lift, or forcing, which is required for the development of

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...

s and

. Convection is very prevalent around shortwave troughs because not only do they provide forcing, but they are also associated with systems that provide other ingredients for the formation of thunderstorms, such as

instability In numerous fields of study, the component of instability within a system is generally characterized by some of the outputs or internal states growing without bounds. Not all systems that are not stable are unstable; systems can also be mar ...

wind shear Wind shear (or windshear), sometimes referred to as wind gradient, is a difference in wind speed and/or direction over a relatively short distance in the atmosphere. Atmospheric wind shear is normally described as either vertical or horizontal ...

, and helicity. Shortwave troughs also cause

severe weather Severe weather is any dangerous meteorological phenomenon with the potential to cause damage, serious social disruption, or loss of human life. Types of severe weather phenomena vary, depending on the latitude, altitude, topography, and atm ...

because the ingredients are usually enhanced by shortwaves because these are stronger than the mean environment and weather systems around them.

References

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External links

What is a shortwave trough?
Haby's Hints.
Shortwave Trough
NWS Glossary. Synoptic meteorology and weather