Digital Elevation Model resolution and its impact on the spatial pattern of rainfall-temperature prediction at the catchment scale: The case of the Mille catchment, Ethiopia

In a mountainous catchment, understanding the interaction between DEM resolution and climatic variables is essential for the accurate spatial interpolation of areal mean monthly and annual rainfall and temperature, which is required as an input for further applications such as hydrological and hydraulic modeling, agriculture, and environmental conservation. This case study applied the geostatistical interpolation technique, kriging with external drift (KED), with a digital elevation model (DEM) with various horizontal resolutions, which were used to assess the effects of the DEM horizontal resolutions on the spatial distributions of rainfall and temperature by focusing on interpolating the mean monthly and annual rainfall and temperature over a spatially diversified catchment. The assessment was undertaken using spatially and temporally complete sampled historical climatic datasets, and consequently, the spatial pattern of monthly and annual rainfall (temperature) from east to the west gradually increases or decreases following the DEM elevation increment along the same direction. As a result, the finer-resolution DEM (90-m SRTM-DEM) had a considerable impact on predicting the mean monthly minimum and maximum temperatures, whereas the resampled 500-m SRTM-DEM performed relatively better in mean monthly and annual rainfall and annual minimum temperature estimation values.