Overview of the POLarimetric Cloud Analysis and Seeding Test (POLCAST) Field Program in Eastern North Dakota

The Polarimetric Cloud Analysis and Seeding Test (POLCAST) is an ongoing field program with the goal of improving the understanding of the impact of hygroscopic cloud seeding at cloud base on continental convective clouds. The study has focused on sampling convective clouds observed in the eastern region of North Dakota. The project specifically focuses on determining if identifiable hygroscopic seeding signatures can be observed in polarimetric radar observables or derived fields. POLCAST is a cooperative study between the North Dakota Atmospheric Resource Board (NDARB), National Center for Atmospheric Research (NCAR), University of North Dakota (UND), and Weather Modification Inc. (WMI). A randomized seeding field program has been conducted for three summer convective seasons (June-July 2008, and June-July 2010, June-August 2012). Polarimetric radar data have been collected by the UND C-Band Polarimetric Doppler Weather Radar (NorthPol). In conjunction with NorthPol observations, a research aircraft operated by WMI has been used for the randomized targeting and has also been used to collect aerosol and microphysical observations. This study focuses on radar data analyses of the randomized seeding cases from the POLCAST field campaigns. A total of 44 cases have been collected in the three study seasons. The radar analysis has focused on applying the NCAR hydrometeor identification (HID) algorithm tuned for C-band observations. Also, for each case, seeded and non-seeded cells are being categorized and a statistical and physical characteristic database has been created. This presentation gives a brief description of the experiment and a summary of the polarimetric radar results from the aggregated randomized case analyses.