Abstract
Abstract. Global hydrological models (GHMs) are a useful tool in the assessment of the land surface water balance. They are used to further the understanding of interactions between water balance components and their past evolution as well as potential future development under various scenarios. While GHMs have been part of the hydrologist's toolbox for several decades, the models are continuously being developed. In our study, we present the HydroPy model, a revised version of an established GHM, the Max Planck Institute for Meteorology's Hydrology Model (MPI-HM). Being rewritten in Python, the new model requires much less effort in maintenance, and due to its flexible infrastructure, new processes can be easily implemented. Besides providing a thorough documentation of the processes currently implemented in HydroPy, we demonstrate the skill of the model in simulating the land surface water balance. We find that evapotranspiration is reproduced realistically for the majority of the land surface but is underestimated in the tropics. The simulated river discharge correlates well with observations. Biases are evident for the annual accumulated discharge; however, they can – at least to some extent – be attributed to discrepancies between the meteorological model forcing data and the observations. Finally, we show that HydroPy performs very similarly to MPI-HM and thus conclude the successful transition from MPI-HM to HydroPy.
Highlights
Hydrological models are used in a large number of research and operational applications
Besides providing a thorough documentation of the processes currently implemented in HydroPy, we demonstrate the skill of the model in simulating the land surface water balance
These range from the catchment scale, e.g. highly calibrated models simulating discharge for one specific river, towards large temporal and spatial scales, e.g. the global analysis of hydrological extremes in long-term climate projections (e.g. Do et al, 2020). Models employed in the latter type of studies belong to the group of global hydrology models (GHMs) which focus on simulating different components of the hydrological cycle for the whole land surface
Summary
Hydrological models are used in a large number of research and operational applications These range from the catchment scale, e.g. highly calibrated models simulating discharge for one specific river, towards large temporal and spatial scales, e.g. the global analysis of hydrological extremes in long-term climate projections Depending on their area of operation, the models differ in terms of processes, and in their technical infrastructure and programming language used They can be designed for stand-alone applications using meteorological forcing data or be an interactively coupled component in Earth system models. While models have come a long way since their initial concepts, there is still ample opportunity for improvement and extension of their functions. Bierkens (2015) identified issues due to missing geospatial data, calibration and input data quality, and recognized the need to increase model resolution and eventually include sociological and economical interactions
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