EURADCLIM: The European climatological high-resolution gauge-adjusted radar rainfall dataset

Accurate rainfall information at high spatiotemporal resolutions is needed for many scientific domains and applications but is often lacking. This is also the case in Europe. While the EUMETNET OPERA ground-based weather radar composite provides strong coverage at the km scale, weather radars generally underestimate rainfall by tens or even more than 50 percent. Moreover, many smaller areas suffer from severe overestimation due to non-meteorological echoes during dry weather (e.g. signal interference, or ground echoes caused by obstacles or refraction of the radar beam). Finally, the quality of European OPERA radar composites is inhomogeneous in time and space. In contrast, rain gauges often provide accurate local rainfall estimates, but their network densities are usually too sparse to capture the spatial rainfall variability, especially at the sub-daily time scale. The best of two worlds is combined if radar rainfall images are merged with rain gauge data.

Project EURADCLIM, funded by KNMI’s multi-annual strategic research programme, addresses the need for an accurate (sub-)daily rainfall product covering Europe. A climatological dataset of 1-h and daily rainfall depths at a 2-km grid is derived, which covers a large part of Europe for the period 2013 through 2019. The starting point is the OPERA gridded radar dataset of 15-min rainfall intensities, which is based on data from approximately 150 radars. EURADCLIM first applies methods to further remove non-meteorological echoes from these images by applying a statistical method and a cloud type mask. Subsequently, the radar composites are merged with a pan-European rain gauge dataset (ECA&D) in order to substantially improve its quality. This also includes the search for obtaining more (sub-)daily rain gauge data.

An exploratory is performed to merge a satellite rainfall product (GPM IMERG) with the radar composite for those regions where gauge data are missing, which would improve the usability of the composite above open water and above land surface areas without gauge data. Further, the climatological rainfall dataset is employed to validate satellite precipitation products for a variety of European climates.

Radar rainfall climatologies are derived, with a focus on the seasonal & diurnal cycle and the occurrence of extreme rainfall across Europe. The high spatial resolution allows to investigate the clustering and spatial extent of rain showers over Europe, which is a hot topic in current climate research and of utmost importance from a climate impact perspective.

It is envisaged to make the derived climatological radar rainfall dataset publicly available. In the end, this dataset will help to reduce Europe’s vulnerability to extreme weather events.

Application potential of derived dataset:

  • Much better reference for validation of weather prediction models (HARMONIE/ECMWF) and satellite precipitation products, which allows for improving them.
  • Better monitoring of (trends in) rainfall extremes and their spatial extent, which is highly relevant for anticipating future extremes in a changing climate.
  • It strengthens KNMI’s pan-European climate services, especially our ECA&D activities
  • Developed methods in EURADCLIM are also relevant for KNMI’s own radar rainfall products and nowcasts. This contributes to the Early Warning Centre and is highly relevant for national stakeholders like water boards, municipalities and the Directorate-General for Public Works and Water Management (Rijkswaterstaat).

 

Figure 1: OPERA radar rainfall map
Figure 1: OPERA radar rainfall map

References:

EUMETNET programma OPERA: https://www.eumetnet.eu/activities/observations-programme/current-activities/opera/
European Climate Assessment & Dataset (ECA&D): http://www.ecad.eu/