The impact of Mediterranean oscillations on periodicity and trend of temperature in the valley of the Nisava River: A fourier and wavelet approach

Periodicity of temperature on three stations in the Nisava River valley in period 1949-2014, has been analyzed by means of Fourier and wavelet transforms. Combined periodogram based on FFT shows considerable similarity among individual series and identifies significant periods on 2.2; 2.7; 3.3; 5; 6-7 and 8.2 years in all datasets. Wavelet coherence analysis connects strongest 6-7 years spectral component to Mediterranean oscillation (MO), starting in 1980s. Combined periodogram of MOI index reveals 6-7 years spectral component as a dominant mode in period 19492014. Wavelet power spectra and partial combined periodograms show absence of 6-7 years component before 1975, after which this component becomes dominant in the spectrum. Consistency between alternation in temperature trend in the Nisava River valley and change in periodicity of  MO was found.