Characteristics of tempo-spatial variations of pan evaporation in China during 1960—2021 based on a homogenized dataset

Based on the Multiple Analysis of Series for Homogenization (MASH) and Climatol homogenization methods, the inhomogeneities in monthly pan evaporation (PE) time series at 573 stations in China during 1960—2021 are detected, estimated, and adjusted. The uncertainties due to different methods are quantitatively evaluated with regard to the number of inhomogeneous stations, breakpoints and shift values. Temporal and spatial variation characteristics in seasonal and annual PE in recent 62 years are revealed based on ensemble homogenized dataset. The results show that compared with Climatol, MASH can detect fewer inhomogeneous stations, more break points but with smaller range of adjustments. The homogenized data indicate that the regional mean spring, summer, and annual PE series show significant decreasing trends with rates of 8.38, 9.83 and 16.83 mm/(10 a), respectively, whereas the winter and autumn series show weak increasing trends of up to 0.27 and 1.10 mm/(10 a), respectively. The rate of change trend tends to be weaker in winter and summer but stronger in spring, autumn and annual. The increase trends occurs at over half stations in winter (57.1% stations) and autumn (60.4% stations), and these stations are mainly located in northeastern and southwestern (except Yunnan) China, the eastern Tibetan Plateau, southern China in winter. In autumn, the stations with increase trend are located at the area from northeastern China to Yunnan, the Tibetan Plateau, and most parts of Xinjiang. On the contrary, the decrease trend prevail at 81.7% stations in spring, especially in Yunnan and over the area from northeastern China to Shandong. 80.8% stations of stations experience the decrease trend in summer in the eastern part to the south of North China. Annual PE shows a decrease trend at 80.3% of stations that are mainly located in northwestern Xinjiang, the central Inner Mongolia, Shandong, southern Hebei, Henan and central Yunnan. The ranges of seasonal and annual trends decrease after adjustment. The number of stations with the rate of decreasing trend less than 10 mm/(10 a) or increasing trend greater than 30 mm/(10 a) decreases, indicating a better spatial consistency of large-scale changes of PE in China after homogenization. Abrupt changes of seasonal PE occurred in the spring of 1977, the autumn of 2018 and the winter of 2020 while an abrupt change of annual PE occurred in 1972 in China. No abrupt change occurred in summer.