Analysis of Potential Evapotranspiration in Heilongjiang Province

Abstract

As the global temperature has been increasing, an intriguing phenomenon has emerged wherein the potential evapotranspiration (PET) in many areas does not show a clear positive correlation with the temperature. Instead, PET is decreasing in various areas, giving rise to the “evaporation paradox”. This phenomenon also occurs in Heilongjiang province. Heilongjiang province is a province in China with a large agricultural output, so it is necessary to explain the mechanism of decreasing pan evaporation in order to cope with the rational use of food and water resources in China. In this paper, the Mann–Kendall (M-K) parameter test and multiple regression analysis were used to analyze the trends and correlation between PET and climate change in Heilongjiang province from 1961–2020. The results show that the potential evaporation in Heilongjiang province had a decreasing trend of 7.776 mm/10 a, and there was a fluctuation in the decreasing trend during 1985–1995 and 2000–2020. Temperature, wind speed, vapor pressure, and solar radiation contributed −87.23%, 88.25%, 65.87%, and 42.53% to PET variation, respectively, highlighting wind speed as the main factor in the decrease in PET, followed by the vapor pressure and solar radiation, whereas temperature-induced changes in PET were neutralized by the former.