A 1970-2010 archive of climate surfaces for the Iberian Peninsula

This dataset is an archive of gridded surfaces of mean maximum, mean and mean minimum temperature, and precipitation, for the Iberian Peninsula. Temporal resolution is of 1 month, and spatial resolution is of 0.0089999994 degrees. The study area ranges from 43.8969994ºN through 35.5000000ºN, and from 9.6999998ºW through 3.5029993ºE. It covers continental Spain and Portugal. There is a total of 1920 grids (40 years x 12 months x 4 variables). The surfaces were interpolated using ANUSPLIN on georeferenced climate records drawn from the Spanish State Agency of Meteorology and the Portuguese Water Resources Information System. Variable networks of input stations were used to interpolate the surfaces, averaging 390 and 1877 points for temperature and precipitation respectively. A fixed configuration was used for all the interpolations: trivariate quadratic spline model with longitude, latitude and elevation as independent variables. A square root transformation was appied to precipitation fields to reduce skewness. The software was made to minimize the Generalized Cross Validation (GCV) error. The signal to data point ratio was below 50% for temperature surfaces, with many values between 25% and 35%. This suggests limitations in the number of input data points which may have resulted in a loss of detail on the interpolated surfaces. This is not necessarily bad in terms of broad spatial patterns, but it does indicate that absolute predictions should be used with caution for fine microclimatic patterns. Root generalized cross validation was usually lower than 1ºC for temperature, reaching up to 0.85ºC for summer months of mean maximum temperature. Absolute errors in precipitation did range from 4.41 mm in July to 12.82 mm in December, but the seasonal pattern of prediction errors was inverse and corresponded to 24% and 13% respectively.