Spatial and temporal patterns of the mean annual precipitation at decadal time scale in southern Italy (Calabria region)

Mean annual precipitation variability at decadal time scale over a southern Italy area (Calabria) was investigated to quantify the spatial and temporal patterns. A multivariate approach has been applied to analyse spatial-temporal (1921-2000) data of annual precipitation. A nested isotropic linear model of coregionalization was fitted to the experimental variograms including three basic structures: a nugget effect, an exponential model and a spherical model. The correlation structure between the decades was analysed by applying principal component analysis at each spatial scale, and specific factors at each characteristic scale were cokriged and mapped. Two components were identified: the first is mainly linked to local factors, which could be identified by the orographic characteristics of the region, while the long range component could be related to large-scale factors, like for example the processes of the global atmospheric circulation. In addition, in order to obtain a better insight into the pattern of relatively dry or wet zones, a standardized relative difference was calculated. The results showed that the annual precipitation decreased during the period 1921-2000 and the spatial distribution changed with an increase of dry areas.