Cyclogenesis

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As Cyclogenesis ( English Cyclo Genesis or cyclone development , development of cyclones or cyclone development ' ) is in meteorology the formation or gain of a low pressure system referred to the formation of cyclones or tropical cyclones favored.

definition

Cyclogenesis is a dynamic process in the atmosphere. This creates a low pressure area within a few days from an initial disturbance in the mean current of the west wind zone . It affects the weather in the middle latitudes. In this way, a thermal wind flowing to the east arises as a medium flow form with strong horizontal temperature gradients between the polar regions and the tropics . The deflection at orographic obstacles creates repulsive forces that move the westerly winds into a wave-like pattern ( Rossby waves ). Strong vertical currents and horizontal convergence and divergence lead to the formation of high and low pressure areas, around which the Coriolis force flows in a circle. The originally symmetrical waves are amplified and distorted with the polar front, which runs in a wedge shape towards the pole. The cold air flowing southwards forms a cold front and the warm air flowing northwards forms a warm front. The faster moving cold front catches up with the warm front and pushes itself under the warm air masses.

Theories of cyclone formation

There are different theories about the formation, development and dissolution of cyclones.

  • The oldest known cyclone theory comes from Robert FitzRoy from the year 1859, He suspected that the meeting of cold and warm air is the cause of a cyclonic vortex.
  • Felix Maria von Exner-Ewarten was of the opinion that an obstacle from cold air flowing to the south forces the warmer air flowing from west to east to form vortices. He dealt intensively with dynamic meteorology and with gravitational waves in the atmosphere.
  • In 1934 Richard Scherhag presented his thesis that a divergence in height favors cyclogenesis near the ground.
  • In the polar front theory of the Bergen school , the cyclones are described as unstable waves along the polar front. In cyclogenesis, baroclinic disorders are considered and the life cycle of an ideal cyclone is drawn up. Critics accuse the model of simplifying reality too much and therefore not being able to make any concrete statements. Therefore, there is also research that describes cyclogenesis more generally on the basis of characteristic tendencies in pressure and temperature fields.

literature

Web links

Commons : Cyclogenesis  - collection of images, videos and audio files

Individual evidence

  1. ↑ Cyclogenesis. In: Lexicon of Physics. Spektrum.de, accessed on May 31, 2020 .
  2. Jump up ↑ cyclone theories. German Weather Service, accessed on May 31, 2020 .
  3. ^ Robert FitzRoy: Notes on meteorology. Board of trade . GE Eyre and W. Spottiswoode for HM Stationery off., London 1859 ( archive.org ).
  4. ↑ Felix M. Exner: Dynamic Meteorology . BG Teubner, Leipzig / Berlin 1917 ( archive.org ).
  5. ↑ Richard Scherhag: On the theory of high and low pressure areas. The importance of divergence in pressure fields . In: Meteorological Journal . tape 51 , 1934, pp. 129-138 .
  6. ↑ Kraus Helmut: The polar front theory . In: The Earth's Atmosphere An Introduction to Meteorology . S. 292–297 ( Text Archive - Internet Archive ).