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Abstract Evapotranspiration ( ET ) is an important component of the global hydrological cycle. However, to what extent transpiration ratios ( T/ET ) are controlled by vegetation and the mechanisms of global‐scale T/ET variations are not clear. We synthesized all the published papers that measured at least two of the three components ( E , T , and ET ) and leaf area index ( LAI ) simultaneously. Nonlinear relationships between T/ET and LAI were identified for both the overall data set and agricultural or natural data subsets. Large variations in T/ET occurred across all LAI ranges with wider variability at lower LAI . For a given LAI , higher T/ET was observed during later vegetation growing stage within a season. We developed a function relating T/ET to the growing stage relative to the timing of peak LAI . LAI and growing stage collectively explained 43% of the variations in the global T/ET data set, providing a new way to interpret and model global T/ET variability.
Wang et al. (Sat,) studied this question.