Evaluation of global terrestrial evapotranspiration in CMIP6 models
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ORIGINAL PAPER
Evaluation of global terrestrial evapotranspiration in CMIP6 models Zhizhen Wang 1,2 & Chesheng Zhan 1
&
Like Ning 1 & Hai Guo 1,2
Received: 8 July 2020 / Accepted: 14 October 2020 # Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Evapotranspiration (ET), which relates to hydrology and the energy cycle process of land surface, is a key link of the water cycle and an important item of expenditure in energy balance. There have been multiple state-of-the-art climate models that were included in Phase 6 of the Coupled Model Intercomparison Project (CMIP6), but the performance in estimating the ET of the models is still unclear. Thus, this study evaluated the global terrestrial ET of CMIP6 models. The performance of the models and CMIP6 ensemble mean was compared with the GLEAM v3.3a dataset, and the uncertainties of the ensemble were evaluated using the signal-to-noise ratio (SNR). The results show that there was no perfect model that could perform optimally in all aspects of the comparison, and the performance of the CMIP6 ensemble was better than that of a single model. MIROC6, CESM2, and EC-Earth3 performed satisfactorily in some aspects, whereas the performance was poor in other aspects. GFDL-ESM4 exhibited a relatively poor performance. Most models and the CMIP6 ensemble overestimated ET, and the estimations of different models varied greatly, but the results of most models showed an increasing trend. The CMIP6 ensemble overestimated ET in most regions of the world and may have smoothened the variation in the model estimations. In high latitudes such as northern parts of North America and Eurasia, results of the CMIP6 ensemble and GLEAM were approximately the same. The uncertainty of the CMIP6 ensemble was generally low and the estimation reliability varied according to the geographical region.
1 Introduction Evapotranspiration (ET), which contains soil and water surface evaporation as well as transpiration, relates to the hydrology and energy cycle processes of the land surface. It is a key link in the water cycle and an important expenditure item in the energy balance budget (Lian et al. 2018). More than 60% of precipitation that falls on the land surface is consumed by ET per year (Oki and Kanae 2006; Pan et al. 2020). Furthermore, ET absorbs heat from the surrounding environment, and therefore, more than 50% of the solar radiation absorbed by the land surface is consumed (Trenberth et al. 2009). Thus, accurate estimations of ET are essential to climate and earth system models (Berg and Sheffield 2019). The land-surface model (LSM) is a generally applied method to simulate ET (Overgaard et al. 2006), and the Coupled
* Chesheng Zhan [email protected] 1
Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
Model Intercomparison Project (CMIP) organized under the auspices of the
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