Seasonal rainfall variations in Spain (1912–2000) and their links to atmospheric circulation

The main aim of the present study is to identify to what degree variability of precipitation in Spain can be attributed to variations in the dominating atmospheric circulation patterns. Statistical models were developed and tested on seasonal precipitation in different regions in Spain during the period 1912–2000. The monthly sea level pressure field (SLP) over the area between the latitudes 30°N and 55°N and longitudes between 25°W and 20°E was used as predictor. Principal components deduced from this field were used as a basis for stepwise multiple regression analysis. The models were developed using even years as a calibration period, while odd years were used as a validation period. Stepwise regression was applied to investigate the relative importance of the predictors. Models reproduce around 68% of the variability in winter precipitation corresponding to western and central Iberian Peninsula, around 20% for Mediterranean coast and 54% for northern coast of Iberian Peninsula. In spring, models reproduce around 57%, 43%, and 27% of the variance for similar regions. In summer and autumn results are worse, although an important fraction of the rainfall variability is captured. The models were then used on the entire period and it is concluded that precipitation changes observed in western Iberian Peninsula during the studied period can mainly be attributed to variations in the SLP field, although topographic effects and/or other causal mechanisms (sea surface temperature, local convective events) must be considered, in addition to SLP field.