Spatio-temporal variation of potential evapotranspiration and climatic drivers in the Jing-Jin-Ji region, North China

Potential evapotranspiration (ET0) is a key component of the water cycle and a main factor to water resources assessment. Analysis of variation in ET0 is significant in understanding the climate change and agricultural water management; It is affected by multiple climatic factors, including air temperature, relative humidity, wind speed, and sunshine duration. To understand the variations of ET0 in the Jing-Jin-Ji region (Beijing Municipality, Tianjin Municipality, and Hebei Province), values of ET0 and other climatic parameters at 22 national meteorological stations from 1961 to 2015 were analyzed. Cramer's test showed a shift point in the ET0 data at approximately 1991. Annual ET0 decreased from 1961 through 1991 at a rate of −20.95 mm per decade, but annual ET0 increased at a rate of 7.40 mm per decade from 1992 to 2015. Partial correlation analysis and multiple linear regression methods were used to determine the dominant climatic driving factors for ET0, and to reveal the causes of change in ET0. From 1961 to 1991, the decrease of wind speed and sunshine duration offset the effect of increased air temperature, leading to reduced ET0. However, from 1992 to 2015, average air temperature was the most dominant factor contributing to the increase in ET0. Increased of air temperature and wind speed, and decreased relative humidity caused an increase in ET0. This change in ET0 could impact hydrological cycle and agriculture irrigation management in the Jing-Jin-Ji region.