The Mistral ( Provençal mistral , Occitan mistral, magistral , Catalan mestral , Corsican maestrale ) is a katabatic wind , i.e. a cold, dry and often strong downdraft from the northwest, which is noticeable in the lower Rhône valley (and beyond). Etymologically, the regionally slightly different names are derived from the respective words for "master" or "masterly".
The term “Mistral” is mainly used in connection with Provence , but the province of Languedoc (east of Montpellier ), the Var ( Fréjus ) department, the entire lower Rhône valley (from Lyon to Marseille ) and the islands of Corsica and Sardinia are also used affected. The eastern part of the Côte d'Azur , the so-called "French Riviera", with the towering mountains, on the other hand, is protected and is almost always spared from the wind, which is usually perceived as unpleasant.
A special characteristic of the Provençal architecture are the wrought iron bell cages on church towers, etc. Their wind-permeable shapes offer significantly less resistance to the mistral than bell gables or pointed helmets .
The mistral can initially blow quite gently and still warmed up by the land mass and therefore warm. After a few hours or even days it can develop into a strong to stormy wind that blows from the northwest over France into the Mediterranean area . Typical is then a cloudless, dark blue sky, good visibility, an impressive starry sky at night and a significant drop in temperature. It can blow for days and occurs so frequently that the trees in the Rhone Valley are often bent in the direction of the wind towards the south (wind fleeing ).
When a low moves east over northern France, the classic starting point for the mistral is given. The wind is generated by polar air flowing into the Mediterranean area . The Alps and Cevennes form a blockade so that the cold polar air reaches the Rhone Valley, a rift valley between the two mountains mentioned. This canalization ( nozzle effect ) creates high wind speeds of 50–75 km / h, with peaks over 135 km / h.
The typical mistral weather situation is characterized by high air pressure over the Bay of Biscay and a low pressure area over Italy . This situation often occurs in connection with cold air ingress from the north, the main thrust of which runs over Great Britain to the north-western Mediterranean region. There the cold air meets the warmer Mediterranean air. This offers favorable conditions for the development of a genoa low .
The very noticeable lenticular clouds are an indication of the sudden onset of the mistral .
|Winds in the Mediterranean|
The Provencal region has 32 winds from all directions, and the mistral is the wind blowing directly from the northwest. The very strong mistral is also called aurassos and a very cold mistral is called cisampo . On the lower reaches of the Ebro , the Mistral is called Cierzo . In Sardinia and Sicily he is called Maestrale . The synonym Cers is used for the mistral in Catalonia , Narbonne and parts of Provence.
The Provencal definition of mistral is inconsistent. For some, Mistral is a north-westerly wind that only blows in the Rhône Valley. Accordingly, it can be further east, e.g. B. on the Côte d'Azur, actually no Mistral. Others also speak of mistral when there are (cold) north winds on the Côte d'Azur.
The same effect arises between the Cevennes and the Massif Central . The resulting wind is called Tramontana and blows in a north-south direction - other sources refer to the mistral as a fall wind from the mountains of the Massif Central, which despite dry adiabatic warming is perceived as cold as it flows into the warmer Mediterranean air.
Mistral and the environment
The Mistral is very dry and removes moisture from the soil, which significantly increases the risk of forest fires in Provence. It causes damage to tree growth, which is particularly important for fruit and olive cultivation, as this is only possible in locations sheltered from the wind. However, it also has advantages for agriculture, as fungal diseases and insect pests can only spread slightly or not at all.
Cork oak shaped by the mistral .
Mistral over the island of Château d'If in front of Marseille.
Spray breakers at Mistral, Plage du Prado .
- Honorin Victoire: Petite Encyclopédie des Vents de France. JC Lattès, Paris 2001, ISBN 978-2709621939
- Valérie Jacq, Philippe Albert and Robert Delorme: Le mistral. Quelques aspects des connaissances actuelles. La Météorologie, Société météorologique de France 2005
- Berthold Wiedersich: Pocket Atlas - Weather . Klett-Perthes Verlag , Gotha, 2003.