Multifractality of the standardized precipitation index: influence of pan evaporation and virtual temperature-based potential evapotranspiration

Hydrological extremes experience an increase in some regions and a decrease other zones. The objectives of the present work were (i) to introduce Class A pan evaporation data virtual temperature-based potential evapotranspiration (PETv hereafter) into Standardized Precipitation–Evapotranspiration Index (SPEIm computation (ii) describe small large fluctuations SPI SPEIm through multifractal detrended fluctuation (MF-DFA) cross-correlation (MF-DCCA) analyses. We used 40 years (1974–2013) monthly rainfall (P), mean, minimum maximum air temperature, (E), relative humidity (RH) sun brightness (RSB). Meteorological variables collected from Puyo meteorological station, Pastaza Province, Ecuador. time series for 1 6 months timescales determined following two approaches. computed values using precipitation as only input variable. Additionally, we incorporated standard SPEI (SPEIm). revealed differences compared with classical methodology. Five out fifteen Asymmetry (AI) positive (0.095 ≤ AI 0.419).This indicates relevance high at different scales. Joint spectra between (1,6)/SPEIm(1,6) versus RH RSB rendered negative which suggests importance low shorter DCCA coefficient allows one identify those scales where are influenced by variables. Long-term correlation sub-Gaussian behaviour (apart temperature) main causes structures.