A first attempt to model global hydrology at hyper-resolution

Abstract. Global hydrological models are one of the key tools that can help meet the needs of stakeholders and policy makers when water management strategies and policies are developed. The primary objective of this paper is therefore to establish a first of its kind, truly global hyper-resolution hydrological model that spans a multiple-decade period (1985–2019). To achieve this, two key limitations are addressed, namely the lack of high resolution meteorological data and insufficient representation of lateral movement of snow and ice. Thus a novel meteorological downscaling procedure that better incorporates fine-scale topographic climate drivers is incorporated, and a snow module capable of lateral movement of frozen water resembling glaciers, avalanches and wind movement is included. We compare this global 30 arc-seconds version of PCR-GLOBWB to previously published 5 arc-minutes and 30 arc-minutes versions by evaluating simulated river discharge, snow cover, soil moisture, land surface evaporation, and total water storage against observations. We show that hyper-resolution provides a more accurate simulation of river discharge, this is especially true for smaller catchments. We highlight that although global hyper-resolution modelling is possible with current computational resources and that hyper-resolution modelling results in more realistic representations of the hydrological cycle; our results suggest that global hydrological modelling still needs to incorporate landcover heterogeneity at the sub-grid scale and include processes relevant at the kilometre scale in search of better predictive capacity to provide more accurate estimates of soil moisture and evaporation fluxes.