Introducing ground-based water vapour profiling to the DWD network: Broadband differential absorption lidar measurements

The current observational coverage of the atmospheric boundary layer (ABL) remains insufficient to improve high-resolution forecasting, including numerical weather prediction (NWP) and nowcasting, particularly for severe weather events. The existing measurement networks cannot provide, at sufficient spatial and temporal resolution, the vertically resolved kinematic and thermodynamic information needed to resolve the ABL for high-resolution forecasting. In order to address this shortcoming, the German Weather Service, Deutscher Wetterdienst (DWD), is currently expanding its operational network to include ground-based vertical profile measurements. Lidar remote sensing profilers are being installed at thirteen selected weather stations across Germany. These stations will complement DWD’s observation systems, such as radiosondes, radar wind profilers, and AMDAR measurements.

Doppler-lidar systems and differential absorption lidars (DIALs) will allow for the continuous retrieval of wind and humidity across the boundary layer. The DIALs, DA10 atmospheric profilers by Vaisala, will be used to provide vertical humidity profiles up to 4 km above ground level based on broadband differential absorption at two wavelengths in the near-infrared spectrum.

As part of their deployment, the DA10 units undergo extensive characterisation and testing. This includes continuous monitoring of the technical parameters alongside the measured water vapour mixing ratio and attenuated backscatter profiles, enabling the simultaneous assessment of operational reliability and data quality across a wide range of meteorological conditions. In conjunction with this monitoring, systematic intercomparisons were conducted both among the DA10 units themselves and against established reference measurements, primarily radiosondes, further strengthening this assessment. Initial results indicate a good overall agreement between the DIALs’ humidity profiles and the radiosonde measurements, while also highlighting the limitations of these commercially available lidars for systematic measurements of ground-based humidity profiles.