Hybrid-regime Doppler Lidar for atmospheric wind profiling: development and performance assessment

Due to the differences in the operational principles and target objects, the coherent Doppler wind Lidar (CDWL) and direct detection Doppler wind Lidar (DDWL) each have their own advantages and disadvantages. To fully leverage the advantages of the two types of wind lidar, a hybrid Doppler wind Lidar (HDWL) named WindMast Trop 15 K, combining coherent-detection and direct-detection schemes, is developed. A data fusion method designed for the HDWL based on real-time fitting prediction (RTFP) is proposed herein. We conducted long-term synchronous observation experiments at the Beijing Nanjiao Meteorological Observatory from June to September 2025 to evaluate the wind measurement accuracy of the HDWL. And three measurement cases were presented to demonstrate the data fusion method's performance. The results indicate that: 1) the HDWL coherent-detection module measurement data are consistent well with the radiosonde measurements, with the correlation coefficient (R²) of wind speed (wind direction) reaching 0.969 (0.993), and the root mean square error (RMSE) is 0.632 m·s^-1 (8.209°). Since the aerosol load above 3 km becomes lower, the data acquisition rate of the coherent-detection module measurements decreases accordingly, and the wind speed error gets larger; 2) The consistency between the HDWL direct-detection module and radiosonde varies within different altitude ranges. Below 2 km, the high concentration and rapid variation of aerosol distribution cause a significant wind speed deviation. Subsequently, with the altitude increasing, the RMSE of wind speed decreases to a minimum of 0.98 m·s^-1 and then increases, while the RMSE of wind direction decreases and stabilizes around 5°; and 3) Compared with the pre-fusion data, the measurement accuracy of wind speed and direction is improved to varying degrees after fusion. Taking the case on September 20, 2025,local time, as an example, the RMSE of wind speed decreased from 0.891 m·s^-1 to 0.506 m·s^-1, with a reduction of 43.2%. The RMSE of wind direction decreased from 4.663° to 3.889°, with a drop of 16.6%. The results verify the effectiveness of the RTFP method.