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The analysis of actual evapotranspiration (ETa) changes is of great significance for the utilization and allocation of water resources. In this study, ETa variability in northern China (aridity index < 0.65) is investigated based on the average of seven datasets (GLEAM, GLASS, a complementary relationship-based dataset, CRA-40, MERRA2, JRA-55, and ERA5-Land). The results show that ETa increases significantly from 1982 to 2017. Limited by water supply, ETa is significantly correlated with precipitation (R = 0.682), whereas the increase in precipitation is insignificant (p = 0.151). Spatially, the long-term trend of ETa is also not completely consistent with that of precipitation. According to a singular value decomposition (SVD) analysis, the trend of ETa is mainly related to the first four leading SVD modes. Homogeneous correlation patterns indicate that more precipitation generally leads to high ETa; however, this relationship is modulated by other factors. Overall, positive potential evapotranspiration anomalies convert more surface water into ETa, resulting in a higher increase in ETa than in precipitation. Specifically, ETa in the northern Tibetan Plateau is associated with meltwater generated by rising temperatures, and ETa in the Badain Jaran Desert is highly dependent on the wet-day frequency. Under global warming, the inconsistency between ETa and precipitation changes has a great impact on water resources in northern China. [ABSTRACT FROM AUTHOR]

In this study, the temporal variation of actual evapotranspiration (AE) over China during 1980–2015 is analysed based on an ensemble of six reanalyses and a complementary‐relationship‐based AE dataset. The results reveal that annual mean AE in China increases significantly, and the major regime shift occurred around 1998. Accordingly, long‐term mean AE changes from 1999–2015 relative to 1980–1997 are computed to quantify the spatial pattern of AE trends. In general, annual AE increases significantly in southern and northwestern China but decreases significantly in northeastern China and eastern Tibetan Plateau. Then we examine the primary cause for changes in AE using the Budyko framework, in which the change of climate is represented by changes in precipitation and potential evapotranspiration and the shift in landscape characteristics is represented by the parameter n. Overall, increasing potential evapotranspiration is the main contributor to the increase of AE in southeastern China. Increasing potential evapotranspiration and the parameter n are the main contributors to the increase of AE in southwestern China. Decreasing AE in northeastern China and eastern Tibetan Plateau are respectively caused by changes in precipitation and the parameter n, whereas the combination of these two factors has led to increasing AE in northwestern China. It is shown here that the contribution of the parameter n is comparable to that of climate change in western China. A positive correlation is found between vegetation coverage and the parameter n; however, vegetation type, catchment slope, irrigation practices, and glacial meltwater also have an impact on regional n. A concurrent occurrence of the negative contribution of parameter n and positive vegetation coverage change is found in the forest land of northeastern and southeastern China. Decreasing irrigation water is likely the main reason for the negative contribution of n in cropland of the North China Plain. [ABSTRACT FROM AUTHOR]

With the motivation to identify whether global warming would lead to an increase in the rate of actual evapotranspiration (AE) over land, an assessment is made of AE variability from an ensemble of seven reanalyses (NCEP‐NCAR, NCEP‐DOE, MERRA, MERRA V2, ERA‐Interim, JRA‐55, and CFSR). By subdividing global land into nine climatic regions using the aridity index (AI), we examine the variability and long‐term trend of regional AE and various related factors. Results indicate that AE shows a significant increasing trend during 1979–2015 in the humid, wet, and arctic regions. Overall, three main parameters, namely, precipitation, surface net solar radiation, and wet‐day frequency, strongly influence the temporal variations of AE over most regions. The possible causes of trends in AE are examined in view of the linear trends of the related meteorological variables. Accordingly, increasing potential evapotranspiration and increasing vapour pressure are the main contributors to increasing AE in humid regions. Increasing temperature is the main contributor to increasing AE in wet regions. Both increasing energy supply and water supply on AE largely explain the significant increasing trend of AE in arctic regions. In view of data availability, a correlation analysis was conducted between AE in individual reanalyses and the results from the Mezentsev–Choudhury–Yang equation and the ensemble of the seven reanalyses. On average, NCEP‐NCAR is the worst among the seven reanalysis datasets in revealing temporal characteristics of AE. [ABSTRACT FROM AUTHOR]

Actual evapotranspiration (AE) is a key component of water cycle. The arid climate of northwest China makes water supply a major constraint on AE. Water source analysis is of great significance to study the causes of AE change. In this paper, we presented an assessment of AE trends in northwest China based on GLEAM (AE_GLEAM), an ensemble of six reanalyses (AE_reanalyses), and a complementary-relationship-based AE dataset (AE_CR). Both AE_GLEAM and AE_reanalyses increased significantly (p < 0.001) during 1981–2017. AE_CR also increased to a certain extent, but the rate was slower. In general, the increasing trends of AE were mainly found in mountainous areas, such as the Altai, Tianshan, Karakoram, Kunlun, Altun, and Qilian Mountains. For these regions, AE was even higher than precipitation in terms of both the climatological mean and the linear trends. It demonstrated that terrestrial water storage (S) could give supplementary supply for AE. Therefore, we extended the Budyko framework to evaluate the effect of S on AE. Taking the landscape parameter n = 1.8 as a reference, S contributed approximately 27% of total water availability for AE. Overall, S seemed to be a major contributor to the increasing AE in the Altai, Tianshan, Qilian, and Altun Mountains. Precipitation was the main source of evaporated water in the western Tianshan to Karakoram Mountains, where potential evapotranspiration also contributed to the increase in AE. In the case of different n values, the contribution from S had a deviation range of −16.9% to 8.5%. This model provides an opportunity to assess the response of AE to S in the absence of observational data. [Display omitted] • Actual evapotranspiration (AE) increased significantly in northwest China during 1981–2017. • The increasing trends in AE were mainly found in mountainous areas. • AE variability was controlled not only by water supply from precipitation but also by other water sources. • Terrestrial water storage (S) contributes approximately 27% of total water availability for AE. • S seems to be a major contributor to the increasing AE in the Altai, Tianshan, Qilian, and Altun Mountains. [ABSTRACT FROM AUTHOR]