Temporal and spatial characteristics of reference evapotranspiration in China

The analysis of the temporal and spatial characteristics of reference evapotranspiration is helpful to understand the distribution and variability of the agricultural and ecological water requirement. Based on the daily meteorological data of more than 200 stations all over China, daily reference evapotranspiration(ET₀) was estimated by using the FAO Penman-Monteith equation. The spatial distribution of ET₀ was obtained by GIS and IDW method was used for spatial interpolation. In China, the largest ET₀ was found to be more than 1500 mm in northwest and south region, and the smallest is found to be 600 mm to 700 mm in the northeast region and Sichuan Basin. In addition, the ET₀ in summer contributes most of a year. Then four representative stations were selected to analyze the temporal variation of ET₀ values and the effects of meteorological data on ET₀. It is concluded that in recent years ET₀ in arid areas tends to become smaller because of the decreases of solar radiation and wind speed, while in humid areas ET₀ is relatively stable.