Spatiotemporal Variations of Reference Evapotranspiration and Its Climatic Driving Factors in Guangdong, a Humid Subtropical Province of South China

It is of great importance to study the changes in reference evapotranspiration (ET0) and the factors that influence it to ensure sustainable and efficient water resource utilization. Daily ET0 data calculated using the Penman-Monteith method from 37 meteorological stations located within Guangdong Province in the humid zone of southern China from 1960 to 2020 were analyzed. The trend analysis and Mann-Kendall test were used to analyze the time series changes in ET0 and major climatic factors (air temperature (T), relative humidity (RH), sunshine duration (SD), and wind speed (u(2))) for over 61 years. Sensitivity and contribution analyses were used to evaluate the driving factors of ET0. The main findings of the study are as follows: (1) the trend in average annual ET0 time series in Guangdong slightly increased at a trend rate of 1.61 mm/10a over the past 61 years, with most stations experiencing an increase in ET0. During the same period, air temperature significantly increased, while RH and SD decreased; u(2) also decreased. (2) Sensitivity analysis showed that ET0 was more sensitive to RH and T than SD and u(2), with ET0 being most sensitive to RH in spring and winter and T in summer and autumn. (3) The contribution analysis showed that T was the dominant factor for ET0 variation in Guangdong, followed by SD. SD was found to be the dominant factor in ET0 changes in areas where the evaporation paradox occurred, as well as in spring and summer. The study concludes that the climate in Guangdong became warmer and drier over the past 61 years, and if the current global warming trend continues, it will lead to higher evapotranspiration and drought occurrence in the future.

Automated summary

Studying the changes in reference evapotranspiration (ET0) and its influencing factors is crucial for sustainable and efficient water resource utilization. This study analyzed daily ET0 data from 37 meteorological stations in Guangdong Province, southern China, from 1960 to 2020. The findings reveal that ET0 slightly increased over the past 61 years, with rising air temperature and decreasing relative humidity and sunshine duration. Sensitivity analysis showed that ET0 was more sensitive to relative humidity and temperature. Contribution analysis indicated that temperature was the dominant factor for ET0 variation in Guangdong. The study concludes that climate in Guangdong became warmer and drier, leading to potential future increases in evapotranspiration and drought occurrences if the global warming trend continues.