# Cloud Seeding Evidenced by Coherent Doppler Wind Lidar
## 4 Application in an Artificial Precipitation Operation  
The method was integrated into the CDWL to support the cloud seeding operation. The field experiment was performed at an airport of Xilin Gol grassland, Inner Mongolia, China (112\({}^{\circ}\)39\({}^{\prime}\) E, 42\({}^{\circ}\)21\({}^{\prime}\) N), from 28 August to 1 October 2019. The velocity azimuth display (VAD) technique was used to retrieve the vertical wind profile. The lidar operated in the VAD scanning mode with an elevation angle of 60\({}^{\circ}\) and a period of 2.5 min. The VAD technique was used to retrieve the vertical wind profile. The azimuth angle scanned from 0\({}^{\circ}\) to 300\({}^{\circ}\), with an angle step of 5\({}^{\circ}\). The CDWL results of cloud, precipitation, windshear, and turbulence intensity during the experiment are given in [51, 53]. A cloud seeding event was conducted locally to accelerate the development of the precipitation process within the clouds. The cloud seeding operation started at 5:30 p.m. local time, 12 September 2019. The seeding was conducted by burning about 60 silver iodide cigarette strips carried by five aircraft. Each strip weighed 4.2 kg, including 125 g of silver iodide. Aircrafts seeded Agl into the cold cloud from the altitude of 4.0-4.5 km to help increase the probability of ice crystal formation and growth into precipitation hydrometeors. The cloud phase is provided by the Advanced Geosynchronous Radiation Imager (AGRI) in FY4A satellites [54], with a spatial resolution of 4 km, as shown in Figure 4. Figure 4a shows the cloud phase across the China region at 5:30 p.m. local time. The seeding was conducted by the five aircraft simultaneously in the target region, which is represented by the yellow square in Figure 4a. Cloud phase distribution of seeding regions at different times are shown in Figure 4b-e. The black triangle indicates the location of the  
Figure 3: Examples of different types of Doppler spectra. **(a)** General aerosol spectrum; **(b)** cloud spectrum; **(c)** spectrum under strong turbulence; **(d–l)** precipitation spectra and its separation results. Circles stand for the raw data of spectra. Black lines represent fitting results. The yellow shadow and light blue shadow represent separated aerosol and rain components, respectively. CDWL. The orange arrows represent the wind vector. Mixed clouds were dominant at the beginning of seeding operation, as shown in Figure 4a. Then the obvious growth of ice crystals was detected after the seeding near the lidar location. Atmospheric profiles provided by the microwave radiometer (MWR) are shown in Figure 5. Application and detail specifications of the MWR are provided in [51]. Temperature, water-vapour, and liquid water content of the seeding region at 5:30 p.m. were \(-\)5.8\(-\)\(-\)9.3 \({}^{\circ}\)C, 2.5-3.2 gm\({}^{-3}\), and 0.12-0.15 gm\({}^{-3}\), respectively. Temperature and water-vapour were decreasing while liquid water content was increasing after the seeding operation. The liquid water content reached 1.22 gm\({}^{-3}\), when precipitation occurred. The cloud seeding is documented by the CDWL, as shown in Figure 6. The cloud base is marked by black circles in Figure 6a. The cloud and wind speeds are shown in Figure 6d-f, which are retrieved by single peak fitting. The detection of the cloud boundary and its velocity contributed to determine the time and position of the seeding operation. Figure 4: Cloud phase provided by FY4A satellite in 12 September 2019, local time. (**a**) shows the cloud phase across the China region at 5:30 p.m. local time, the yellow square indicates the seeding region. (**b–e**) show cloud phase distribution of seeding regions at different times. The black triangle indicates the location of the CDWL. The orange arrows and black triangle represent the wind vector and the location of the CDWL, respectively. Figure 5: Continuous MWR observation results during 12\(-\)13 September 2019. Before the cloud seeding, the cloud base moves downward from about 6 km to 3 km.