Time trends of daily maximum and minimum temperatures in Catalonia (ne Spain) for the period 1975–2004

Daily maximum and minimum temperatures, Tmax and Tmin, and diurnal temperature range, DTR, from 37 temperature stations in Catalonia (NE Spain) are analyzed to detect significant daily time trends for the period 1975–2004. The homogeneity of the series is tested by means of the Standard Normal Homogeneity, the Buishand range and the Pettitt tests. The lack of randomness of the series, suggesting time trends, is also investigated by means of the Von Neumann ratio test. The daily time trends obtained and their spatial and temporal patterns are mainly in agreement with overall time trends recently derived for the Northern Hemisphere. The results indicate generalized increasing annual trends of daily Tmax and Tmin (0.5 °C/decade), especially relevant in spring and summer, with values reaching 0.8–0.9 °C/decade, and also remarkable for Tmax in winter (0.7 °C/decade). In autumn, however, average trends point at a decrease in Tmax (−0.5 °C/decade). As a result, an average annual decreasing trend of DTR is found, particularly relevant in autumn (−0.9 °C/decade). Several periods with an outstanding number of stations showing significant positive time trends are detected and analyzed during the spring and summer seasons both for daily Tmax and Tmin. The only period with a relevant number of significant negative trends is detected in February for daily Tmin, thus implying a significant increasing trend of DTR during this short winter period. Comparisons are established with large‐ and regional‐scale temperature trends, paying attention to the west Mediterranean atmospheric dynamics change. Copyright © 2009 Royal Meteorological Society