Relationships between Reference Evapotranspiration and Meteorological Variables in the Middle Zone of the Guadalquivir River Valley Explained by Multifractal Detrended Cross-Correlation Analysis

• Published in: Fractal and fractional Vol. 7; no. 1; p. 54
• Main Authors: Gómez-Gómez, Javier, Ariza-Villaverde, Ana B., Gutiérrez de Ravé, Eduardo, Jiménez-Hornero, Francisco J.
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-01-2023
• Subjects: Algorithms; Climate change; Climatic changes; Correlation analysis; Cross correlation; Evapotranspiration; Exponents; Fractals; High temperature; Humidity; meteorological factors; multifractal cross-correlations; persistence; Radiation; reference evapotranspiration; Relative humidity; scaling exponents; Solar radiation; Time series; Trends; Valleys; Variables; Weather; Wind speed; Spain; Guadalquivir River
• ISSN: 2504-3110; 2504-3110
• DOI: 10.3390/fractalfract7010054

The multifractal relationship between reference evapotranspiration (ET0), computed by the Penmann-Monteith equation (PM), relative humidity (RH) and mean surface temperature (Tmean) was studied in the middle zone of the Guadalquivir River Valley (south Spain) in a previous study. This work extends that study to the average wind speed (U2) and solar radiation (SR), focusing on more recent years. All agro-meteorological variables were analyzed by multifractal detrended cross-correlation analysis (MFCCA) and multifractal detrended fluctuation analysis (MFDFA). The outcomes revealed persistent long-term autocorrelations, with Tmean and RH having the highest persistence (H>0.75). More precise results of multifractal properties than in the previous study were obtained for ET0, Tmean, and RH due to the elimination of trends in the signals. Only medium and large fluctuations in ET0 showed multifractal cross-correlations with its controlling factors, except for U2. Moreover, joint scaling exponents differed from individual exponents. These phenomena contrast with what has been observed in previous cross-correlation studies, revealing that some differences exist in the dynamics of multifractality among the analyzed variables. On the other hand, the Tmean–ET0 relation showed that extreme events in ET0 are mainly ruled by high temperature fluctuations, which match conclusions drawn in the previous study.