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Abstract: Evapotranspiration is an important flux term in the water cycle that integrates atmospheric demands and surface conditions. Thus, analysis of the temporal variation of reference evapotranspiration (ET0) will help us to understand climate change and its effect on hydrology. In this paper, we present an analysis of the monthly ET0 at 15 stations during 1961–2005 in the Taoer River basin in China, calculated by the FAO Penman–Monteith method. We derived the growing season and annual total ET0 time series and using the Mann–Kendall method, moving t test and Morlet wavelet conducted comprehensive time series analysis to characterize significance test, abrupt change and period in the ET0 data sets. The results present that: (i) in terms of the seasonal cycle, monthly ET0 reaches its peak in May and growing season ET0 accounts for 60.7% of annual total. Long term growing season ET0 fluctuates in accordance with annual ET0, both having turning points in 1982 and 1993; (ii) with respect to the long term persistence, the trends for growing season and annual ET0 show the same spatial patterns: high positive values in the west study area in the upper reach and negative values in the Southeast study area in the lower reach. The spatial distribution of annual tendencies suggests an influence from the altitude and latitude; (iii) for individual station, abrupt changes in annual ET0 are more pronounced than those in growing season ET0. The timings for the abrupt changes in ET0 series at individual stations are consistent with those in regional ET0. Abrupt changes detected in the early 1980s are all increasing changes, while those in earlier 1990 are all decreasing changes; and (iv) based on the Morlet wavelet analysis, there exist significant periods of 1, 3 and 7.3 years in annual ET0 series and significant 1 year period and 7.3 years period in growing season ET0 series. Maximum air temperature, mean air temperature, relative humidity and bright sunshine hours are main climate variables responsible for the periodicity in ET0. [Copyright &y& Elsevier]

In this paper, future drought characteristics (frequency, duration and intensity) over China are analysed by using four climate models from CMIP6 under the seven SSP-RCP (shared socioeconomic pathway-representative concentration pathway) scenarios (SSP119, SSP126, SSP434, SSP245, SSP460, SSP370, and SSP585) for three defined periods of 2021–2040 (near-term), 2041–2060 (mid-term) and 2081–2100 (long-term). The corresponding four climate models output from CMIP5 are also used to conduct a comparison analysis between CMIP5 and CMIP6 to address the improvements added to CMIP6 in terms of drought identification. The drought characteristics are identified by applying the standardized precipitation-evapotranspiration index (SPEI) at a 12-month timescale and run theory. The results show that CMIP6 has a robust capability to capture historical (1986–2005) drought characteristics. For the future period of 2021–2040, the decrease in precipitation and increase in potential evapotranspiration will lead to continuous dry conditions in the upper and middle Yangtze River basin and eastern Pearl River basin. Relative to the reference period, drought events will be more frequent and severe with longer durations in the Northwest River basins and middle Yangtze River basin. Furthermore, higher emissions signify a greater increase in drought frequency and intensity in the long-term period. Except for the SSP585 scenario, the lower emission scenario corresponds to the higher drought duration soon and in the mid-21st century (2021–2060). This finding is regarded as a "strange phenomenon", which cannot be detected by the previous CMIP5-based emission scenarios (RCP2.6, RCP4.5 and the unlikely pathway RCP8.5). Therefore, additional "possible future"-based scenarios (SSP119, SSP126, SSP434, SSP245, SSP460, and SSP370) should be included in extreme climate studies, especially for the near future and mid-21st century. Notably, compared with CMIP5, the reduced biases in drought characteristics are more likely associated with improvements in the representation of physical processes in climate models from CMIP6. The results of this study could provide a basis for the development of drought adaptation measures over China. • Latest CMIP6 climate models and seven SSP-RCP scenarios are used to analyze the possible changes in droughts over China. • More robust projections will be presented by CMIP6 than CMIP5, due to the better representations in physical processes. • The higher emission signifies shorter drought duration, lower precipitation and PET in mid-21st century over China. [ABSTRACT FROM AUTHOR]