Radiant weather

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As radiation weather designating meteorology a form of high pressure weather with low cloud and at most moderate winds.

Due to the lack of disturbing winds , solar radiation dominates the weather and the temperature of the air and the ground near the ground. The values ​​of the radiation balance are very large - positive during the day, negative at night - and lead to considerable fluctuations in the temperature of the land surface and the air close to the ground, which vary greatly in time and space and lead to local diurnal wind systems . Similar effects ( land and sea wind ) occur on sea ​​coasts and on the banks of larger rivers and inland waters .

The soil - especially dry or rocky soil without vegetation - heats up very strongly during the day and leads to the formation of thermal slope winds in the mountains . Because of the cooling at night , these winds are reversed (see mountain and valley wind circulation ).

While z. For example, glider pilots appreciate such wind systems because of their often hours-long updrafts , but the nighttime cooling - especially in autumn and early spring - can have serious consequences for fruit and wine growing . Therefore there are z. B. at the Wachau (Lower Austrian Danube Valley) in typical weather conditions real early warnings .

Cold air lakes

In basin locations and depressions, inversion weather patterns with very persistent fog often develop in radiation weather, especially in the winter half-year . In such foggy areas (e.g. the Bohemian or Klagenfurt Basin ), the daily fluctuations in the radiation balance and temperature are minimal, but due to the often weeks of calm , the air pollution is particularly high during the heating season .

For agricultural meteorology z. B. the Neuwied basin and the Moselle valley are interesting. As soon as the upper basins of the Eifel or Hunsrück are filled with cold air, this can overflow into the Moselle valley. In addition to the threat of frost damage, there is also the risk of pests due to the increased humidity , which can be fought thermally, with wind machines and sometimes with helicopters.

Where rivers flow from a basin through a narrow valley into lower levels , the radiant weather can trigger special regional winds. One such case is the Böhmwind near Dresden : the air cooled in Bohemia flows through the Elbe gorge down to Saxony, where it stays on the northwest side of the Ore Mountains and often leads to heavy haze or fog. Only when the wind changes generally to the south-west does the Bohemian wind break and the cold air lake in the Elbe valley can be cleared.