1Universidade de Caxias do Sul. RS. - Brasil
2Lab. Física de la Atmósfera. Instituto de Medio Ambiente. Universidad. de León - Spain
In the Mediterranean area summer precipitation is scarce and the need of water for the population and for agricultural and industrial activities is constantly increasing. The problem is more acute in the southwest of Europe, since millions of tourists visit the area every summer and demand large amounts of water. The precipitation over the Iberian Peninsula presents a strong seasonal pattern. In summer the rainfall is mainly caused by convective thunderstorms.
There has been a pattern of continued aridity since the late 1960s trough North Africa. This effect is most persistent in the western region. Is this same trend now being detected in the Mediterranean region of Western Europe? Thus, the question is: Are there changes in the summer precipitation trends of the Iberian Peninsula? In order to answer these questions it is essential to carry out a careful analysis of the precipitation trends on a regional scale.
Therefore, it is necessary to use techniques to identify climate trends and non-climatic variations. The model employed to detect the climatic trends has taken into account the following factors:
• The initial analysis of the monthly precipitation series during the summer in more than 1500 meteorological stations of the Iberian Peninsula (Spain) over the period between 1961 and 1990.
• The selection of as many stations as possible with at least 90% of complete data in their summer precipitation series.
• The filling-in of the missing data in order to obtain complete series.
• The application of a homogeneity test in order to detect abrupt changes caused by non-climatic factors such as a replacement or a relocation of the station or some alteration in the observing procedures.
• The application of a model that identifies climatic trends in the 333 meteorological stations that were selected.
• The application of a model that groups together spatially the stations that present climatic trends.
The results show an increase in the precipitation in the months of July and August in wide areas of the south of Spain, which may by attributed to an increase of the convective phenomena.