when do the mistral winds blow in provence
Mistral (wind) The mistral is usually accompanied by clear, fresh weather, and it plays an important role in creating the climate of Provence. It can reach speeds of more than 90 km/h (56 mph), particularly in the Rhône Valley. Its average speed during the day can reach about 50 km/h (31 mph), calming noticeably at night. The mistral usually blows in winter or spring, though it occurs in all seasons. It sometimes lasts only one or two days, frequently lasts several days, and sometimes lasts more than a week.[5]
High-pressure area Highs are frequently associated with light winds at the surface and subsidence through the lower portion of the troposphere. In general, subsidence will dry out an air mass by adiabatic, or compressional, heating.[8] Thus, high pressure typically brings clear skies.[9] During the day, since no clouds are present to reflect sunlight, there is more incoming shortwave solar radiation and temperatures rise. At night, the absence of clouds means that outgoing longwave radiation (i.e. heat energy from the surface) is not absorbed, giving cooler diurnal low temperatures in all seasons. When surface winds become light, the subsidence produced directly under a high-pressure system can lead to a buildup of particulates in urban areas under the ridge, leading to widespread haze.[10] If the low level relative humidity rises towards 100 percent overnight, fog can form.[11]