Complexity and Predictability of Daily Actual Evapotranspiration Across Climate Regimes

Abstract

AbstractEstimation of actual evapotranspiration (ETa) is challenging due to its complex interactions with surrounding environments; thus, understanding the complexity and predictability of ETa along with its influencing factors is essential to improve ETa estimation. Based on the FLUXNET and ChinaFLUX datasets, we first examined whether daily ETa exhibited chaotic behaviors, and then investigated how daily ETa complexity and predictability varied across climate regimes and ecosystems using the chaos theory. The results of recurrence plot and correlation dimension (CD) analysis suggested the existence of chaotic behaviors in daily ETa, implying the system controlling ETa processes was deterministic with a limited number of controlling variables. The recurrence quantification analysis further revealed a varying degree of complexity for ETa processes (e.g., determinism‐DET with a range from 0.01% to 40.7%) across the sites. Specifically, daily ETa featured stronger deterministic properties (e.g., higher DET and lower CD values) and thus higher predictability in humid and arid regions; whereas, higher degrees of daily ETa complexity emerged in sub‐humid and semi‐arid regions due to more complex interactions with environmental factors. Moreover, primary environmental controls on daily ETa complexity varied with climatic and land surface conditions. Results showed that energy and water supplies along with average daily temperature and relative humidity were the primary controls on the ETa complexity across the sites, while leaf area index also played an important role at drier sites. As a first attempt, this study provides additional avenues to understand the complexity of ETa processes from a global perspective using the chaos theory.