# Cloud Seeding Evidenced by Coherent Doppler Wind Lidar
###### Abstract  
Evaluation of the cloud seeding effect is a challenge due to lack of directly physical observational evidence. In this study, an approach for directly observing the cloud seeding effect is proposed using a 1548 nm coherent Doppler wind lidar (CDWL). Normalized skewness was employed to identify the components of the reflectivity spectrum. The spectrum detection capability of a CDWL was verified by a 24.23-GHz Micro Rain Radar (MRR) in Hefei, China (117 deg15' E, 31 deg50' N), and different types of lidar spectra were detected and separated, including aerosol, turbulence, cloud droplet, and precipitation. Spectrum analysis was applied as a field experiment performed in Inner Mongolia, China (112 deg39' E, 42 deg21' N ) to support the cloud seeding operation for the 70 th anniversary of China's national day. The CDWL can monitor the cloud motion and provide windshear and turbulence information ensuring operation safety. The cloud-precipitation process is detected by the CDWL, microwave radiometer (MWR) and Advanced Geosynchronous Radiation Imager (AGRI) in FY4A satellites. In particular, the spectrum width and skewness of seeded cloud show a two-layer structure, which reflects cloud component changes, and it is possibly related to cloud seeding effects. Multi-component spectra are separated into four clusters, which are well distinguished by spectrum width and vertical velocity. In general, our findings provide new evidence that the reflectivity spectrum of CDWL has potential for assessing cloud seeding effects. D 26 July 202  
guishing between the impacts of cloud seeding and the natural variability of weather systems on the cloud-precipitation process [15], which requires multi-platform simultaneous observations [4; 16]. For instance, only two of 36 experiments for seeding effects were confirmed by the research aircraft, radar, and surface instrumentation, mainly due to the natural fluctuations in ice crystal concentrations [17]. Radars are widely applied to obtain supercooled cloud seeding processes [5; 18; 19]. After AgI being released, the processes of supercooled liquid converting into ice particles, subsequent growing into precipitation are analyzed by combined with in-situ measurements and radar [20]. Satellites play an important role in detecting some seeding effects, such as Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), Ice, Cloud, and land Elevation Satellite (ICE-Sat) [21; 22; 23; 24; 25]. Other measurements such as polarization lidar [26; 27; 28], unmanned aerial vehicles [29], C- and W-band dual-polarization radars [30; 31] can help ice cloud detection and the tracking of cloud seeding. The process of cloud seeding has strong complexity and variability in time and space. More detection methods need to be developed in order to obtain details of the cloud phase transformation and ice crystal evolution with high spatial and temporal resolution. The Doppler wind lidar as an active optical remote sensing instrument measures the radial velocity accurately; these are primarily applied in detecting windshear [32], turbulence [33; 34; 35; 36], aircraft vortex [37], fog [38; 39], the atmosphere boundary layer [40], and gravity waves [41] under clear air conditions [42; 43; 44; 45]. Recently, lidars have been extended to precipitation detection for their ability to detect the aerosol and precipitation signals simultaneously under rain conditions [46; 47; 48; 49; 50]. By deep analysis of the power spectrum, the CDWL can provide precise wind and rain detection with high spatial and temporal resolutions [51]. Based on accurate spectral measurements, the CDWL has the potential to reflect cloud phases, and thus it can be developed as a new way for cloud seeding detection. In this work to support the cloud seeding operation, a CDWL was applied to detect wind, precipitation, and clouds simultaneously. The paper is organized as follows: the instruments are described in Section 2. In Section 3, the verification experiment using a CDWL and a MRR is presented.