Gridded data set of the stable isotopic composition of precipitation over the eastern and central Mediterranean

An attempt is made to produce 10' x 10' gridded data sets of the isotopic composition of precipitation across the central and eastern Mediterranean. Following previous studies, statistical models are developed using all existing isotopic data from the area, aggregated on seasonal and annual bases. Various combinations of geographical and meteorological parameters are examined. Initial gridded isotopic data sets are obtained by applying these models to gridded geographical and meteorological data. The residuals of the models are interpolated into the desired grid, using ordinary kriging, and the result is added to the model-derived grids, to provide the final gridded isotopic data sets. Goodness of fit statistics are used to select the best combination of model and residual interpolation method using an independent data set consisting of annual averages. Finally, an estimation of the uncertainty of the gridded isotopic values is attempted. Overall, the produced grids are quite successful in representing the observed patterns as well as the actual values of stable isotopes in precipitation at the studied area.