Cold air drops

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As cold air drops denote meteorologists a height low in the upper troposphere .

construction

It consists of very cold air of polar origin, typically has a horizontal extent of 300 to 1000 km and is located 5,000 to 10,000 meters above sea ​​level . A drop of cold air is not recognizable as a low pressure area on the ground ; at most it is noticeable through a slight cyclonic bulge of the isobars . A drop of cold air also has no fronts . But when it passes through, about the same weather phenomena can be observed as with a low, only in the reverse order:

  • Front : Particularly in winter cloud formations with showers like a cold front, otherwise cloud decline or loosening clouds due to sinking processes.
  • Back side : Area of ​​closed slip-up clouds with precipitation that is sometimes longer-lasting than with a warm front - not as pronounced in summer.
  • Center : Low altitude temperatures cause a high level of instability, therefore often deep cloud cover with showers and thunderstorms, especially in summer. The weather situation that led to the so-called Heinrich flood in northern Hesse, eastern Westphalia and southern Lower Saxony in July 1965 is an example of such a severe thunderstorm.

A barometer on the ground can indicate high pressure despite the presence of a drop of cold air and thus suggest “nice weather”. Most of the time, however, it is very cloudy and the long-lasting eddies created at high altitude can cause violent thunderstorms and snowfalls in winter.

behavior

The behavior of cold air droplets still gives the model calculations great difficulties. It is difficult to predict which exact direction of pull it will take - or whether it is largely stationary. Experience shows that they follow the current on the ground, for example. A prognosis for weather situations in which cold air drops are involved therefore contains a high uncertainty factor. Sometimes it is difficult to estimate the weather development for the next 24 to 36 hours.

Gota Fría

In Spain , drops of cold air repeatedly cause intense precipitation and storms, especially in autumn. When the Mediterranean is still relatively warm and at a low altitude south of Spain, a lot of rising moisture can be carried over the Spanish mainland by the counterclockwise rotating air masses. If several factors play a role (air pressure in lower altitudes, jet streams , orography, etc.) storms occur, which are called Gota Fría after the Spanish translation for cold air drops . Since Gota Fría has been used increasingly as a term for any type of heavy rain since the 1980s, Spanish meteorologists have started to call drops of cold air as depresión aislada en niveles altos (DANA, German isolated high altitude ).

See also

literature

  • Roger P. Frey: Thunderstorm. Flight meteorology from AZ . 5th edition. Self-published, Bern 2016, ISBN 978-3-03302636-0 .

Individual evidence

  1. ↑ Benito Fuentes: De qué hablamos exactamente cuando decimos "gota fría". In: elpais.com . October 19, 2018, accessed January 20, 2020 (Spanish).