Impact of climate change on potential evapotranspiration under a historical and future climate scenario in the Huang-Huai-Hai Plain, China

Climate change is widely accepted to be one of the most critical problems faced by the Huang-Huai-Hai Plain (3H Plain), which is a region in which there is an over-exploitation of groundwater and where future warmer and drought conditions might intensify crop water demand. In this study, the spatiotemporal patterns of ET₀ and primary driving meteorological variables were investigated based on a historical and RCP 8.5 scenario daily data set from 40 weather stations over the 3H Plain using linear regression, spline interpolation method, a partial derivative analysis, and multivariate regression. The results indicated a negative trend in all the analysed periods (except spring) of the past 54 years of which only summer and the entire year were statistically significant (p < 0.01) with slopes of −1.09 and −1.29 mm a⁻¹, respectively. In contrast, a positive trend was observed in all four seasons and the entire year under the RCP 8.5 scenario, with the biggest increment equal to 1.36 mm a⁻¹ in summer and an annual increment of 3.37 mm a⁻¹. The spatial patterns of the seasonal and annual ET₀ exhibited the lowest values in southeastern regions and the highest values in northeastern parts of Shandong Province, probably because of the combined effects of various meteorological variables over the past 54 years. Relative humidity (RH) together with solar radiation (RS) were detected to be the main climatic factors controlling the reduction of ET₀ in summer, autumn, and the entire year on the 3H Plain. ET₀ in spring was mainly sensitive to changes in RS and RH, whereas ET₀ in winter was most sensitive to changes in wind speed (WS) and decreased due to declining RH. Under the future RCP 8.5 scenario, the annual ET₀ distribution displays a rich spatial structure with a clear northeast–west gradient and an area with low values in the southern regions, which is similarly detected in spring and summer. The most sensitive and primary controlling variables with respect to the increment of future ET₀ are in the first place RS and then mean temperature in spring, while they turn to be mean temperature and then RS in summer. In autumn, future ET₀ is most sensitive to RH changes. WS and RH are the controlling variables for ET₀ in winter. Annual future ET₀ is most sensitive to RH changes, and accordingly, RS is responsible for the predicted increment of the annual ET₀. Better understanding of current and future spatiotemporal patterns of ET₀ and of the regional response of ET₀ to climate change can contribute to the establishment of a policy to realize a more efficient use of water resources and a sustainable agricultural production in the 3H Plain.