Preprints
https://doi.org/10.5194/egusphere-2025-3617
https://doi.org/10.5194/egusphere-2025-3617
08 Sep 2025
 | 08 Sep 2025
Status: this preprint is open for discussion and under review for Geoscientific Model Development (GMD).

GeoDS (v.1.0) : a simple Geographical DownScaling model for long-term precipitation data over complex terrains

Jean-Baptiste Brenner, Aurélien Quiquet, Didier Roche, Didier Paillard, and Pradeebane Vaittinada Ayar

Abstract. Global climate models offer the most comprehensive description of the climate system and its internal processes to date but current computational capabilities typically restrict their spatial resolution to the order of tens of kilometers when multi-decennial or longer simulations are required. For climate applications, it is notoriously difficult to generate high spatial resolution data over long timescales (typically millennial). Over the years, various downscaling techniques have been developed to generate fine scale data from climate models outputs but they often exhibit important limitations when applied over long periods of time. Building on previous efforts, we present a simple topography-based model (GeoDS) to downscale precipitation fields in complex areas, adapted to paleoclimate studies involving multi-millenia simulations. With a limited amount of inputs from a climate model and high resolved geographical information, the model computes, for each time step and every grid point, a topographic exposure index used to distribute precipitation into a high-resolution spatial grid. This dimensionless quantity represents the exposure of surfaces to dominant windward incoming airflows, assumed to bring most of the humidity, and only depends on large scale winds and terrain configuration. The model is first tested under current climate conditions over part of the European Alpine region due to the availability of field data for comparison ; the complexity of both regional topography and climate conditions making it a good test of the proposed methodology. The relative effects of the model’s parameters are assessed as well as the capacity of GeoDS to reproduce the spatial precipitation distribution of a well-resolved gridded target dataset. Despite uncertainties regarding the correct wind fields to choose as input, and the dependency of the model to the temporal resolution of the large-scale data to downscale, we show that the procedure is able to capture most of the patterns occurring at fine spatial scale while being computationally inexpensive. We also demonstrate that the physical base underlying our work grants the model valuable robustness when used outside the calibration framework. This notably opens promising prospects for the application of GeoDS in paleoclimate contexts while providing a flexible, open source and well documented downscaling tool for the climate community.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. While Copernicus Publications makes every effort to include appropriate place names, the final responsibility lies with the authors. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
Share
Jean-Baptiste Brenner, Aurélien Quiquet, Didier Roche, Didier Paillard, and Pradeebane Vaittinada Ayar

Status: open (until 03 Nov 2025)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Jean-Baptiste Brenner, Aurélien Quiquet, Didier Roche, Didier Paillard, and Pradeebane Vaittinada Ayar

Data sets

GeoDS downscaled datasets Jean-Baptiste Brenner https://doi.org/10.5281/zenodo.16420096

Model code and software

Code of GeoDS Jean-Baptiste Brenner https://doi.org/10.5281/zenodo.17045252

Jean-Baptiste Brenner, Aurélien Quiquet, Didier Roche, Didier Paillard, and Pradeebane Vaittinada Ayar
Metrics will be available soon.
Latest update: 08 Sep 2025
Download
Short summary
Due to the limited spatial and temporal coverage of observations, global models are essential tools to study climate. However, long-term climate data at fine spatial scale are difficult to obtain because of elevated computational costs such algorithms involve. This paper presents a simple model based on the description of climate/topography interactions to generate local precipitation fields at low cost. The objective is to provide a flexible and easy to use method for paleoclimate studies.
Share