Time-Series Analysis of Isotope Composition of Precipitation in Zagreb, Croatia

Air temperature and precipitation data (1976–2021), stable isotope composition (δ18O, δ2H) data, and deuterium excess (1980–2021) data were analyzed using principal component analysis (PCA), Fourier analysis (FA), and wavelet analysis (WA). The PCA represented each month by a single dot in the diagram, and month 1 and month 7 were clearly distinguished. The FA and WA gave the 12-month period for all parameters, but the strongest power was for temperature, then δ18O and δ2H, and finally for the precipitation amount and deuterium excess. Both Pearson’s r and Spearman’s ρ correlation coefficients gave similar values for δ2H—δ18O and temperature—δ2H, δ18O correlations.