The effects of urbanization, geographical and topographical conditions on reference evapotranspiration

The effects of climatic changes owing to urbanization, geographical and topographical conditions on FAO Penman–Monteith (FAO P–M) reference evapotranspiration (RET), and energy and aerodynamic terms of RET have been studied. In this study, 56 climatological stations including the Seoul metropolis in South Korea have been selected, and the area of study site was set at 314 km². The climatological station is centrally located in the study area with a 10 km radius. The geographical and topographical characteristics of these sites were examined using GIS analysis. Land use status of the study area was also examined to estimate the extent of urbanization. The study results indicated that the variation of RET rate is closely related to urbanization in most climatological stations. The level of change in RET was higher in areas with higher urbanization rates. As topographical slope of study area increases, RET decreases. Average elevation of the study area also shows the negative correlation with RET. As the wet land area increases, RET decreases. When considering the effect of proximity of the observation station to sea, the closer the observation station is to the sea, the higher the RET. The study results showed that climatic change due to proximity of the observation station to sea had the greatest effect on RET.