Spatio‐temporal variability of reference crop evapotranspiration at different timescales in Sichuan Province, south‐west China*

摘要

Abstract Aiming to analyse the variation of seasonal reference crop evapotranspiration (ET0) and show the impact of meteorological factors on ET0 across Sichuan Province, this study mainly discussed the variation of ET0 during the periods of 1967–2016 in three subregions of Sichuan Province with the Mann–Kendall test (MK), Morlet wavelet analysis and path analysis. Meanwhile, future ET0 trend variation characteristics at different timescales were evaluated by Hurst exponents based on the rescaled range analysis (R/S) method. The results indicated that over the past 50 years, annual ET0 had a decreasing trend with a rate of −0.64 mm per10 years, confirming the existence of an ‘evaporation paradox’. Through spatial analysis, the distribution of average annual ET0 exhibited a declining trend from south to north over the study region. On the seasonal scale, the highest values of ET0 in summer were distributed in the Sichuan central basin while the highest values in other seasons were in the south‐western mountain area. The Hurst exponents showed that the trends of annual and seasonal ET0 in the future are consistent with past ones in the whole region (H > 0.5). The annual ET0 showed the obvious periodic variation of 28 years in the study regions based on Morlet wavelet analysis. The decreases in ET0 were mostly attributed to the decline in sunshine hours. These findings can help water managers in better water planning and irrigation scheduling for local agricultural production.