Spatial-temporal variation of evapotranspiration and meteorological factors in Japan from 1961 to 2023

Abstract

Evapotranspiration is an important component of the hydrological cycle, and its trends affect water management and agricultural production. In this study, potential evapotranspiration was calculated based on meteorological data from 137 stations in Japan from 1961 to 2023 using the Penman method, and changes over time were examined for each JMA (Japan Meteorological Agency) meteorological district. The results showed that temperature, sunshine duration, and evapotranspiration tended to increase nationwide. To evaluate the characteristics of temperature, relative humidity, and evapotranspiration by region, the mean values for 1961–1963 and 2021–2023 and the differences between them are plotted on a distribution map. The results show an increasing trend of temperature and evapotranspiration over the inland areas of the Japanese islands during the 60-year period. Evapotranspiration increased by up to 300 mm per year. No increasing trend in annual precipitation was observed, suggesting that some soils may potentially become drier. On the other hand, relative humidity tended to decrease in the inland areas and increase in the coastal areas.