Look Up! New study reveals how weather radars can be used to create vertical profiles through snow and rain from near the ground towards cloud top.

Will I need an umbrella on my way home? Will it stay dry during the garden party this evening? Everyone is probably familiar with the radar rain forecast from the weather app. It is an indispensable source of information for short-term precipitation forecasts within the next few hours. For Germany, the data behind is provided by the 17 weather radars of the German Weather Service (DWD; E.g. image above of the radar tower at DWD Observatory at Hohenpeißenberg). These are evenly distributed across the country, from the summit of the Feldberg in the south to the island of Borkum in the north. In order to create extensive precipitation maps everywhere, these radars usually send their signals flat across the landscape while rotating. The echoes of the signal from raindrops and snowflakes are used to create a two-dimensional image of the precipitation every five minutes.
In addition, there are other radars in Germany that observe the atmosphere. So-called cloud radars are mostly located at universities or research institutions. Their data is not visible in the weather app, but is used to answer research questions about the formation of clouds, weather, and precipitation. To do this, these radars usually send their signals vertically upwards. This creates vertical profiles through the weather systems, providing detailed information from the formation of small ice crystals at the top of a cloud to precipitation on the ground (see recent science highlight).

In fact, most European weather radars also “look” upwards once every 5 minutes. Until now, this has only been used for signal calibration. As part of the “PROM” research collaboration, scientists from LMU/MIM and the DWD began systematically storing this vertical data for the 17 German radars four years ago. A new study published in the Bulletin of the American Meteorological Society now shows how the DWD's weather radars, although not originally intended for this purpose, will be able to provide a similar vertical perspective to research radars. A direct comparison between cloud radars and weather radars shows that although the latter only provide a profile every 5 minutes, they can still resolve many characteristics of both stratiform and convective weather conditions. For example, the melting layer (i.e., the transition from snow to rain), riming processes of snowflakes, or even hail can be clearly identified in the profiles. The great advantage of weather radars is their wide availability. For example, the Cloudnet Platform currently lists 5 permanent research stations with cloud radars in Germany, compared to 17 weather radars operated by the DWD. Across Europe, there are currently 162 such radars in operation. This opens up the possibility of large-scale climatological comparisons of weather phenomena as well as the possibility of observing rare phenomena, such as heavy hail, in vertical sections. At the same time, vertical information, e.g., about the exact location of the melting layer, can also improve the interpretation of classic weather radar products such as the precipitation maps. In order to make the vertical data from these radars usable for meteorological purposes, neither investments in new hardware nor compromises in established measurements are necessary; a software adjustment is sufficient.

This study thus also provides an example of how cooperation between university research and weather services can work to give existing measurement networks a literally new perspective.

Author: Paul Ockenfuß

Literature:

• Frech, M.; Kneifel, S.; Ockenfuß, P. & Gergely, M.: Exploring the untapped potential of operational weather radars for vertical profiling of precipitation and clouds. Bulletin of the American Meteorological Society, American Meteorological Society, 2026, 107(1), E127–E141. https://doi.org/10.1175/BAMS-D-24-0113.1