The Polarimetric Cloud Analysis and Seeding Text (POLCAST) was a cloud seeding research experiment that was conducted to help determine if hygroscopic seeding could be detected directly by polarimetric observation or through derived polarimetric parameters. The operational phase of the program, a... Show moreThe Polarimetric Cloud Analysis and Seeding Text (POLCAST) was a cloud seeding research experiment that was conducted to help determine if hygroscopic seeding could be detected directly by polarimetric observation or through derived polarimetric parameters. The operational phase of the program, a cooperative study between the North Dakota Research Board (NDARB), University of North Dakota, Weather Modification Inc., and Ice Crystal Engineering, was conducted from 10 July - 5 August 2006. The study was centered on the measurements recorded by the University of North (UND) C-Band polarimetic Doppler Radar (NorthPol). Hygroscopic flares, deployed on a Weather Modification Incorporation (WMI) aircraft, were used in the study. Ice Crystal Engineering provided these flares. From the polarmetric radar observations, liquid water content, rainfall rates and hydrometeor type were analyzed. The radar-estimated liquid water content retrievals indicated an increase in 7 of the 8 cases after hygroscopic seeding. In correspondence, the rainfall rates were also higher along with the durations of the cells in the seeded cases. The differential reflectivity decrease after seeding, which is an indication that rain drops were decreasing on average in size. The reflectivity also increased after seeding except at cloud base where there was a decrease in reflectivity after seeding. The hydrometeor identification results were in good agreement with the trends observed in reflectivity and differential reflectivity fields. Show less
