On the Attribution of Changing Reference Evapotranspiration in a Coastal Area of China

摘要

Reference evapotranspiration ( ET 0 ) is a crucial parameter for hydrological modeling, land-atmospheric interaction investigations and agricultural irrigation management. This study investigated changes in ET 0 and attributed those changes to climate variations in a coastal area (Zhejiang province) of China by a numerical experiment method. The results indicated that annual ET 0 increased significantly ( p 0.05) at a rate of 1.58 mm·year ?1 from 1973 to 2013, which was mainly caused by an obvious increase in ET 0 in spring. Air temperature and water vapor pressure deficits increased significantly ( p 0.05) at rates of 0.04 °C·year ?1 and 0.005 kPa·year ?1 , respectively, at an annual time scale during the study period, while wind speed and solar radiation decreased significantly ( p 0.05) at rates of ?0.01 m/s·year ?1 and ?3.94 MJ·m ?2 ·day ?1 ·year ?1 , respectively. The contributions of changes in air temperature, wind speed, water vapor pressure deficits and solar radiation to increases in ET 0 were 0.39, ?0.56, 2.62 and ?0.61 mm·year ?1 , respectively. The decrease in wind speed and solar radiation negatively affected the increase in ET 0 , which was offset by the positive effects of the air temperature and water vapor pressure deficits increase, where the water vapor pressure deficits was the dominant factor in increasing ET 0 in the coastal area. Moreover, the impact of topography on ET 0 was further discussed. ET 0 changes at plain stations were approximately 5.4 times those at hill stations, which may be due to the impact of a large water body and the augment of surface roughness from intense human activities in the well-developed plain area. The results are helpful for investigating spatial and temporal changes in the evaporative demand for well-developed regions under energy-limited conditions.