Assessment of a Broadband Differential Absorption Lidar for use in measurement networks and data assimilation

Improving convective-scale forecasts requires more detailed and continuous observational data of thermodynamic profiles and wind profiles in the atmospheric boundary layer (ABL) than currently available. To meet these data requirements, DWD is establishing a network of various surface remote sensing systems targeted on ABL-profiling for routine network operation. This involves integrating 13 Doppler lidars for observing wind profiles and 13 broadband differential absorption lidars (DIALs) for observing water vapor profiles into the network at selected surface stations across Germany until end of 2027.

This contribution reports the results from the assessment of the DIAL, the DA10 from Vaisala, for water vapor profiling network performance and its ability to improve the boundary-layer moisture in a limited-area numerical weather prediction system. The Vaisala DA10 instrument is designed to provide operational water vapor profile observations in the ABL, without the need for calibration. We operate two DA10 units at the Observatory Lindenberg to evaluate all aspects of instrument reliability, operational sustainability, data quality, and on the potential benefit for the NWP using assimilation experiments. Our methods include comparisons with radiosounding observations (4 per day) over at least one year of continuous observations, as well as observation-minus-background statistics between the DA10s and the regional model system ICON-D2 to identify observation errors and to evaluate the model performance with respect to boundary-layer moisture, e.g., under convection. Furthermore, we present first results from assimilating the DA10 water vapor profiles into the kilometer-scale ensemble data assimilation system (KENDA).

Summarizing, this presentation provides an overview of the DA10 network's operational viability for monitoring water vapour profiles 24/7 and for providing additional information for convective-scale data assimilation.