Sun in the Antipodes: Temporal Behavior and Trends of Sunshine Duration in the Iberian Peninsula

• Main Authors: Josep Calbó, Arturo Sanchez-lorenzo, Javier Martin-vide
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.590.5378; http://www.ub.edu/gc/Documentos/Calbo_et_al_IGU_Brisbane.pdf

Abstract: A number of series of sunshine duration for the period 1951-2004, corresponding to main weather stations in the Iberian Peninsula, are analyzed in this study. First, the series were checked for their homogeneity, and some of them were withdrawn from the further analyses. With the remaining data, at monthly, seasonal, and annual resolution, a mean series representing the whole peninsula was computed in order to perform temporal analyses. The series of annual sunshine duration shows a negative, but not significant, trend. However, the trend is not monotonic during the analyzed period: it is negative during the first part of the period (what could be the signal of the phenomenon known as global dimming), and then, clearly positive in the most recent years. This behavior is also found for most of the monthly and seasonal series, in particular in spring and summer. Significant trends are found for some monthly series, and also for some monthly series of the Mediterranean climate regions (found after applying a Principal Component Analysis). Spectral analysis techniques (FFT, MESA) were also applied to sunshine duration data, and two significant peaks, of about 2.5 and 5 years, were found. In addition, the influence of the North Atlantic Oscillation (NAO) on sunshine duration was explored. Results of this latter analysis show that there is a high positive correlation between NAO index and sunshine duration in winter months, for all stations of the Iberian Peninsula except for some in the Northern areas. 1.