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Discovery[ edit ] After the eruption of the Krakatoa volcanoweather watchers tracked and mapped the effects on the sky over several years. They labelled the phenomenon the "equatorial smoke stream".
Oishi's work largely went unnoticed outside Japan because it was published in Esperanto. American pilot Wiley Postthe first man to fly around the world solo inis often given some credit for discovery of jet streams. In the year before his death, Post made several attempts at a high-altitude transcontinental flight, and noticed that at times his ground speed greatly exceeded his air speed.
Jet streams wander laterally dramatically, and have large changes in their altitude. The jet streams form near breaks in West jet case study tropopause, at the transitions between the Polar, Ferrel and Hadley circulation cellsand whose circulation, with the Coriolis force acting on those masses, drives the jet streams.
The Polar jets, at lower altitude, and often intruding into mid-latitudes, strongly affects weather and aviation. The northern Polar jet stream is said to "follow the sun" as it slowly migrates northward as that hemisphere warms, and southward again as it cools. Jet streams are typically continuous over long distances, but discontinuities are common.
Each large meander, or wave, within the jet stream is known as a Rossby wave planetary wave. Rossby waves are caused by changes in the Coriolis effect with latitude.
For example, in andBritain experienced severe flooding as a result of the polar jet staying south for the summer. Cause[ edit ] Highly idealised depiction of the global circulation. The upper-level jets tend to flow latitudinally along the cell boundaries. Extratropical cyclone and Thermal wind In general, winds are strongest immediately under the tropopause except locally, during tornadoestropical cyclones or other anomalous situations.
If two air masses of different temperatures or densities meet, the resulting pressure difference caused by the density difference which ultimately causes wind is highest within the transition zone.
The wind does not flow directly from the hot to the cold area, but is deflected by the Coriolis effect and flows along the boundary of the two air masses.
The balance of forces acting on an atmospheric air parcel in the vertical direction is primarily between the gravitational force acting on the mass of the parcel and the buoyancy force, or the difference in pressure between the top and bottom surfaces of the parcel.
Any imbalance between these forces results in the acceleration of the parcel in the imbalance direction: The balance in the vertical direction is referred to as hydrostatic.
Beyond the tropics, the dominant forces act in the horizontal direction, and the primary struggle is between the Coriolis force and the pressure gradient force.
Balance between these two forces is referred to as geostrophic. Given both hydrostatic and geostrophic balance, one can derive the thermal wind relation: If two air masses, one cold and dense to the North and the other hot and less dense to the South, are separated by a vertical boundary and that boundary should be removed, the difference in densities will result in the cold air mass slipping under the hotter and less dense air mass.
The Coriolis effect will then cause poleward-moving mass to deviate to the East, while equatorward-moving mass will deviate toward the west.
The general trend in the atmosphere is for temperatures to decrease in the poleward direction. As a result, winds develop an eastward component and that component grows with altitude. Therefore, the strong eastward moving jet streams are in part a simple consequence of the fact that the Equator is warmer than the North and South poles.
One factor that contributes to the creation of a concentrated polar jet is the undercutting of sub-tropical air masses by the more dense polar air masses at the polar front.
This causes surface low pressure and higher pressure at altitude. At high latitudes, lack of friction allows air to respond freely to the steep pressure gradient with low pressure at high altitude over the pole. This results in the formation of planetary wind circulations that experience a strong Coriolis deflection and thus can be considered 'quasi-geostrophic'.Dear Twitpic Community - thank you for all the wonderful photos you have taken over the years.
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The cyclone that brought about the devastating winds that battered the UK in the great storm of October was exceptional in both its strength and path across the south of the country.
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