Gulf Stream & Jet Stream | CivFanatics Forums
Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some . The thermal wind relation does not explain why the winds are organized into . Normally, the jet stream flows east over the Gulf of Mexico and turns. The jet stream off the East Coast of the United States controls an overturning circulation, a mega-current that includes the Gulf Stream. The line between the field of cold-core eddies and the warm water of the jet current defines the northern limit of the province after the Gulf Stream has detached.
Rossby waves are caused by changes in the Coriolis effect with latitude.
Jet stream - Wikipedia
For example, in andBritain experienced severe flooding as a result of the polar jet staying south for the summer. 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'.
Tropical air rises to the tropopause, and moves poleward before sinking; this is the Hadley cell circulation. As it does so it tends to conserve angular momentum, since friction with the ground is slight.
Air masses that begin moving poleward are deflected eastward by the Coriolis force true for either hemispherewhich for poleward moving air implies an increased westward component of the winds  note that leftward deflection in the southern hemisphere. Other planets[ edit ] Jupiter 's atmosphere has multiple jet streams, caused by the convection cells that form the familiar banded color structure; on Jupiter, these convection cells are driven by internal heating.
In models, as one increases the planetary radius, holding all other parameters fixed, the number of jet streams decreases. Hurricane protection[ edit ] Hurricane Flossie over Hawaii in Note the large band of moisture that developed East of Hawaii Island that came from the hurricane.
The subtropical jet stream rounding the base of the mid-oceanic upper trough is thought[ citation needed ] to be one of the reasons most of the Hawaiian Islands have been resistant to the long list of Hawaii hurricanes that have approached. For example, when Hurricane Flossie approached and dissipated just before reaching landfall, the U. The term jet stream in these contexts thus usually implies the northern polar jet stream. Aviation[ edit ] Flights between Tokyo and Los Angeles using the jet stream eastbound and a great circle route westbound.
The location of the jet stream is extremely important for aviation. Properties[ edit ] The Gulf Stream proper is a western-intensified current, driven largely by wind stress.
In the oceanographer Henry Stommel noted that "very little water from the Gulf of Mexico is actually in the Stream". When this current interacts with the northeastern coast of South America, the current forks into two branches. The trade winds blow westward in the tropics,  and the westerlies blow eastward at mid-latitudes. This flows along the western boundary of the ocean basin, outweighing the effects of friction with the western boundary current, and is known as the Labrador current.
It transports water at a rate of 30 million cubic meters per second 30 sverdrups through the Florida Straits.
As it passes south of Newfoundlandthis rate increases to million cubic metres per second. It is weaker, however, than the Antarctic Circumpolar Current. The current velocity is fastest near the surface, with the maximum speed typically about 2.
The cooling is wind-driven: Wind moving over the water causes evaporationcooling the water and increasing its salinity and density. When sea ice forms, salts are left out of the ice, a process known as brine exclusion.