Hourly precipitation fields at 1 km resolution over Belgium from 1940 to 2016 based on the analog technique

Abstract. High-resolution gridded precipitation data is scarce, especially at time intervals shorter than daily. However hydrological applications for example benefit from a finer temporal resolution of rainfall information. In this context, we introduce an hourly precipitation dataset for Belgium, featuring a resolution of 1 km. An hourly high-resolution gridded precipitation product over Belgium can provide valuable insights into the dynamics of both short-term and long-term rainfall events, which can be used for wide-ranging applications.

A high resolution precipitation grid of hourly precipitation data for Belgium covering the period from 1940 to 2016 using the analog technique, is created. The analogs are sampled from the period 2017–2022 for which high resolution radar data precipitation fields are available. The initial step involves identifying the criteria, i.e. atmospheric parameters such as atmospheric pressure, temperature and humidity, that can be used to determine analogous days. These atmospheric parameters are obtained from the ERA5 observational data provided by the European Centre for Medium-Range Weather Forecasts (ECMWF). In a second step, hourly precipitation data for suitable analog days are extracted from the radar database, and then used to create the high resolution grid of hourly precipitation for Belgium from 1940 to 2016. Data from rain gauges on the terrain were used for validation of the candidate precipitation analogs.

The dataset compiled for this project provides a top 25 analog days for 1940–2016 based on similarities in weather patterns. The analogs are ranked based on how closely they match to their target day.

The database is relying on the Zarr archiving format and is composed of two archives. A first archive contains all target days together with the 25 best analogs. The second one provides a precipitation field for each hour of every day in the past, representing the hourly median of the analog ensemble. The Zarr format of the database allows slicing through the database. For example, it allows one to easily delimit a specific area of interest and a specific time frame for which the high resolution gridded median hourly precipitation fields are needed. The median field dataset is available on Zenodo (https://doi.org/10.5281/zenodo.14965710) (Debrie et al., 2025).