Spatiotemporal Distribution Characteristics and Influencing Factors Analysis of Reference Evapotranspiration in Beijing-Tianjin-Hebei Region from 1990 to 2019 under Climate Change

Reference evapotranspiration (ET0) is an important part of the water and energy cycles during crop growth. Understanding the influencing factors and spatiotemporal variations of ET0 is of positive significance for guiding regional water-saving irrigation and regulating agricultural production. Data for daily meteorological observations of temperature, relative humidity, wind speed, and sunshine hours from 40 surface meteorological stations and the methods of climate tendency rate, Morlet wavelet, M-K mutation, path analysis, sensitivity analysis, and contribution rate analysis were utilized, to analyze the spatiotemporal distribution characteristics and influencing factors in the Beijing-Tianjin-Hebei region from 1990 to 2019. The ET0 from 1990 to 2019 was 958.9 mm, and there was a significant downward trend in the climate tendency rate of -3.07 mm/10 a. The ET0 presents a spatial distribution pattern decreasing from southwest to northeast. A change in the Beijing-Tianjin-Hebei region's interannual ET0 occurred in 2016, with a decrease of 41.12 mm since then. The ET0 was positively correlated with temperature, wind speed, and sunshine hours, and negatively correlated with relative humidity; among those, wind speed and temperature are the dominant factors affecting the change of ET0. This study provides a scientific basis for the regulation and control of agricultural production in the Beijing-Tianjin-Hebei region.