The uniform flow of the upper-air westerlies is frequently disturbed by the formation of large undulations, called upper-air waves (or Rossby waves). The waves develop in a zone of contact between cold, polar air and warm, tropical air.
It is by means of the upper airwaves that warm air of low latitudes is carried far north at the same time that cold air of Polar Regions is brought equatorward. In this way horizontal mixing, or advection, develops on a gigantic scale and serves to provide heat exchange between the equatorial region of energy surplus and the polar regions of energy deficit.
Associated with the development of such upper airwaves at altitudes of 30,000 to 40,000 ft (10,000 to 12,000 m) are narrow zones in which wind streams attain velocities up to 200 to 250 knots (350-450 km per hr). This phenomenon. named the jet stream, consists of pulselike movements of air following a broadly curving track. In cross section the jet may be likened to a stream of water moving through a hose, the centre line of highest velocity being surrounded by concentric zones of less rapidly moving fluid.
The jet stream is an important factor in the operation of jet aircraft in the range of their normal cruising altitudes. In addition to strongly increasing or decreasing the ground speed of the aircraft, there is a form of air turbulence that at times reaches hazardous levels. This is clear air turbulence (CAT); it is avoided when known to be severe in intensity.
Locals hypothesize that the legacy of Italian blood and culture in Cologne, colonized by the Romans more than 1500 years ago, makes the people more jovial and lighthearted. Cologne is the largest city on the Rhine.
Kolsch is not only the dialect spoken here but, also the name of their own top-fermented beer. There are more than 4,000 pubs, restaurant's and brewery taverns in Cologne.
Unlike many of the world's large cities, Cologne, with a population of over a million, gets better every day, there are more things to do and see, more new and innovative buildings... more
Travel is an opportunity to learn, whether geography, languages, history or other subjects.
Cologne is situated on the beautiful Rhine River.