Hydrologic Impacts of Surface Elevation and Spatial Resolution in Statistical Correction Approaches: Case Study of Flumendosa Basin, Italy

The role of surface elevation and spatial resolution in statistical correction approaches for temperature and precipitation forcing is investigated using four global climate model (GCM) and regional climate model (RCM) combinations. A Mediterranean basin characterized by steep orography and prone to extreme flooding is chosen as a test case. For this aim, precipitation is statistically downscaled using a parametric scheme for bias correction and high-resolution downscaling and a widely used nonparametric approach, with nominal resolution equal to that of the GCM/RCM. Temperature fields are reprojected from climate model to terrain elevation at high resolution. The response of the basin in terms of discharge, actual evapotranspiration, and leakage is simulated using the TOPographic Kinematic APproximation and Integration (TOPKAPI-X) model from 1951 to 2099 and at multiple spatial scales. To investigate the role of orography, simulations are run applying the downscaling schemes on a flat terrain. The results show that, independently of the size of the basin, the elevation factor minimally affects the simulated hydrological response, whereas the effect of the spatial resolution of downscaled precipitation fields on the hydrological budget components is significant, and depends on the catchment size.