Rainfall trends over 40 years in the Cobres River basin, Portugal: variability and impacts

摘要

Climate change has been the most important topic in climatic research of the last few decades around the world. Global warming and, therefore, changes in annual precipitation, have attracted the attention of the researchers in different regions of the world. One of the most significant consequences of the identified global warming would be an increase or decrease in the magnitude and frequency of annual precipitation generated (Santos and Morais 2013). Changes in annual precipitation have been identified in many studies conducted at local, regional or global scales (Silva et al. 2013). The main objective of this study is analysis of the trends in annual precipitation at a regional scale over 40 years (1960-2000) in the Cobres River basin, southern Portugal (37°28'N-37O57'N, 8°10'W-7°51'W), using statistical tools. This region is a typical semi-arid basin, middle-sized with an area of 1194 km~2, located in Alentejo province, an area suffering from desertification. It is a region of relatively low relief, with elevation varying from 103 to 308 m a.s.l. The climate in this region is characteristically Mediterranean and Continental, with moderate winters and hot and dry summers, a high daily temperature range, and a weak and irregular precipitation regime; mean annual precipitation of raingauge stations in the region varies between 400 and 900 mm, with around 50 to 80 rainy days per year.