An Indirect Validation of National and International Gridded Precipitation Products in Northern Italy through Rainfall-Runoff Model Application

Accurate meteorological forcings are a fundamental component for reliable hydrological modelling. Gridded meteorological products offer spatially distributed information facilitating hydrological model applications. In addition, they are often available at large scale (e.g. regional or continental scale), easing the application on large samples of basins, and generally enhancing the replicability of the experiments. Nevertheless, the accuracy of these products varies, and it must be rigorously assessed to ensure the validity of model simulations. This study aims to evaluate the accuracy of four gridded meteorological products: three based on ground observations (E-OBS, SCIA, and ARCIS) and one reanalysis (ERA5-Land), across a large sample of over 150 catchments in three administrative regions of Northern Italy. To assess their reliability, we adopt an indirect evaluation method. This involves assessing the performance of a conceptual hydrological model, which is forced with each of the four gridded meteorological products, over the selected catchments. The E-OBS dataset, developed by the ECAD project, offers climatic variables at a 0.1 x 0.1 (~11 x 11 km) resolution from 1950 onwards across Europe. ERA5-Land is a global scale reanalysis dataset from ECMWF which provides data at a 9 x 9 km resolution from 1950. Finally, ARCIS (Pavan et al., 2019) and SCIA (Desiato et al., 2007) datasets are Italian meteorological products, respectively at 5 x 5 and 10 x 10 km spatial resolution, starting from 1961. For the study catchments, four distinct meteorological forcings, including the daily time series of areal mean precipitation, temperature, and potential evapotranspiration, were estimated using each of the four gridded products. Daily streamflow data were collected from three different regional agencies managing hydroclimatic data and were manually validated. The rainfall-runoff model used for the indirect validation is the CemaNeige-GR6J (Coron et al., 2023), a daily lumped and continuously simulating model. We investigate the performances of the model in simulating streamflow, in order to get insights on the reliability of the gridded products across the region and along the years. Model performances are also analysed against catchment features (such as orography and presence of upstream reservoirs) and data set characteristics (such as gauge network density) to investigate whether certain conditions influence the representativeness of the gridded products and the corresponding streamflow simulations, enhancing our understanding of their applicability and limitations. References Coron, L., Delaigue, O., Thirel, G., Dorchies, D., Perrin, C. and Michel, C. (2023). airGR: Suite of GR Hydrological Models for Precipitation-Runoff Modelling. R package version 1.7.4, doi: 10.15454/EX11NA, URL: https://CRAN.R-project.org/package=airGR. Desiato, F., Lena, F., Toreti, A. (2007). SCIA: a system for a better knowledge of the Italian climate. Bollettino di Geofisica Teorica ed Applicata, 48(3), 351-358. Pavan, V., Antolini, G., Barbiero, R., Berni, N., Brunier, F., Cacciamani, C., ... Torrigiani Malaspina, T. (2019). High resolution climate precipitation analysis for north-central Italy, 19612015. Climate Dynamics, 52, 3435-3453.