[Spatiotemporal variations and attribution analysis of reference evapotranspiration in the Fenwei Plain under climate change]

Reference crop evapotranspiration (ET₀) is a crucial variable for estimating the ecological water demand of vegetation. Under climate change, the trends of ET₀ change vary in different regions. The study of spatial and temporal variations in ET₀ and attribution analysis at the regional scale is more conducive to the regional agricultural water management and ecological water demand estimation under the changing environment. We analyzed the change trend, spatial distribution and the contribution of meteorological factors to annual ET₀ change of the Fenwei Plain during a historical period (1985-2015) and a future period (2030-2060) based on the latest climate data and high-precision grid data from the Sixth International Coupled Model Intercomparison Project (CMIP6). The results showed that the meteorological data from CMIP6 could be used for the prediction of ET₀ after bias correction, and that the prediction accuracy of the multi-model ensemble approach (R² of 82.9%, RMSE of 14.9 mm) was higher than that of a single climate model. ET₀ in the Fenwei Plain showed a significant decreasing trend in the historical period, but a non-significant increasing and significant increasing trend in the future period under the SSP245 and SSP585 scenarios, respectively. The vapor pressure deficit had the largest contribution to the ET₀ change in both the historical and future periods, and was the primary meteorological factor affecting the ET₀ change in the Fenwei Plain under the climate change. Solar radiation and wind speed were important meteorological factors affecting the ET₀ change in the historical period, while temperature and wind speed were the important meteorological factors affecting the ET₀ change in the future period. The meteorological factors that had great contribution to ET₀ change were due to the larger multi-year relative change rates, rather than the high sensitivity of these meteorological factors to ET₀. The ET₀ of the plain under the SSP245 and SSP585 scenarios increased by 4.2% and 3.1% in the future period, respectively, compared with the historical period. The differences in the spatial distribution of the result were mainly from the eastern and western regions of the plain. Based on the high-precision spatial and temporal distribution of ET₀, the spatial and temporal data could be used as a reference for the development of various adaptation for climate change in the Fenwei Plain.