In this study, an assessment is made of the trends of actual evapotranspiration (AE) over China under global warming from an ensemble of the following data sets: National Centers for Environmental Prediction‐National Center for Atmospheric Research reanalysis I, National Centers for Environmental Prediction‐Department of Energy reanalysis II, Modern‐Era Retrospective Analysis for Research and Applications (MERRA), MERRA Version 2, European Centre for Medium‐Range Weather Forecasts Interim Re‐Analysis, and Japanese 55‐year Reanalysis. For China as a whole, annual AE exhibited a significant increasing trend from 1979 to 2015, and the rate of increase was highest in autumn and lowest in summer. By subdividing China into six climatic regions using the aridity index, significant increasing trends in AE are found over the hyperarid, arid, and humid regions, but slightly decrease over the dry subhumid and subhumid regions. For the hyperarid and arid regions, the increases in potential evapotranspiration and the water supply from melting glaciers due to both climate warming and human activities might be the main contributors to the AE increases. An increase in potential evapotranspiration driven by global warming is the main cause of the increased AE over the humid region. On a seasonal basis, most AE over China occurs in summer. However, increasing AE trends have been observed mainly in autumn and winter, and the increase is statistically significant over all of China's six climatic regions in winter. In view of data availability, reanalyses are compared with the results from Mezentsev‐Choudhury‐Yang equation (AE_Budyko). The correlations between individual reanalyses and AE_Budyko tend to be higher over the arid region.

This study identifies a strengthened relationship between the subtropical Indian Ocean dipole (SIOD) during January–February–March (JFM) and the following autumn Indian Ocean dipole (IOD) after the late 2000s. Following the positive SIOD, the northwesterly wind anomalies help to maintain positive sea surface temperature (SST) anomalies in the southwestern tropical Indian Ocean by wind‐evaporation‐SST (WES) feedback during June–July–August (JJA). The anomalous northwesterly winds and the sustained positive SST anomalies promote the development of the zonal wavenumber‐3 pattern (ZW3P) and induce low‐level convergence in the mid‐latitude central southern Indian Ocean, leading to the anticyclone circulation over the northern Indian Ocean by the local Hadley circulation during JJA. The accompanying central equatorial easterly wind anomalies appear in JJA, which is the key to trigger a positive IOD event through Bjerknes feedback. This mechanism for the enhanced SIOD‐IOD relationship is independent from the El Niño‐Southern Oscillation (ENSO).

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.

The aim of this study is to explore the long‐term trends in the distribution of global monsoon precipitation over recent decades using the Global Precipitation Climatology Project (GPCP) data set. In addition, the potential4 mechanisms are examined by applying the atmospheric moisture budget decomposition method to the outputs from the ERA‐Interim medium‐range weather forecasting reanalysis produced by the European Centre for Medium‐Range Weather Forecasts (ECMWF). Changes in global monsoon precipitation are primarily thermodynamically caused by changes in specific humidity and dynamically caused by changes in circulation, as well as by changes in moisture transport that are driven by transient eddies and local evaporation. The results show that the increasing trends in global summer monsoon precipitation from 1979 to 2016 were dominated by contributions from the southern Asian, South African, and North American monsoon regions and were driven by the response of atmospheric circulation to the enhanced east–west thermal contrast in the tropical Pacific. We find that changes in the sea surface temperature (SST) patterns promote increased low‐level vertical velocities in monsoon regions, leading to moisture convergence through divergent circulation anomalies when combined with the climatological humidity field. Hence, the processes result in increasing trends in monsoon precipitation. In addition, evaporation makes increasing contributions to monsoon precipitation throughout the world, except in the South American monsoon region. Moreover, subtropical regions in the East Pacific (the Atlantic) may be major sources of water vapour that have supported increases in precipitation over the southern Asian and North American monsoon regions (the South African monsoon region) in recent decades.

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.

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.