Changements climatiques régionaux dans la France de l'Ouest
Résumé
An analysis of two series of pluviometric observations (1881-1910 and 1961-90) for stations of western France shows an increasing contrast between seasons: while winter is more and more rainy, the frequency of drought arises in summer (specially in august). This is particularly obvious for the last period (1946-95); if this is a climatic trend, its effects could be a real problem for the years to come in areas of intensive agriculture. At the same time this change is associated to an increase of heavy rains in may, june and september. This paper investigates the possible impact of new agricultural methods that have considerably modified the repartition of bare soils during the vegetative season. Thermographies issued from NOAA-AVHRR satellites show higher temperatures in regions where cereals and re-allocation of land have been generalized. This could lead to an important increasing of air masses instability during stormy meteorological situations, and would explain the higher frequency of heavy rains observed nowadays.