Summary

In April 1999, SSSF's Mobile GLASS supported the Cloud Seeding project for Harold Orville and Richard Farley from the South Dakota School of Mines and Technology (SDSMT). Scientists at SDSMT develop and use various types of models to simulate the formation and development of convective clouds under various atmospheric conditions. The models have been applied to several atmospheric situations including cloud seeding by silver iodide or dry ice or hygroscopic particles and their effect on rainfall and hailfall from various types of clouds. The results of these model runs are then compared with observations made by aircraft, radar and ground instrumentation. The main purpose of the Cloud Seeding project was to test, via numerical simulation, several hypotheses having to do with the effectiveness of cloud seeding in augmenting precipitation from orographic cloud systems. To do this one first has to be able to simulate the location and amounts of natural precipitation to be expected. Soundings with the Mobile GLASS were therefore made in and around the Black Hills to measure temperature, humidity and winds to help assess the initial conditions to be specified in the model. In addition data were also collected by the North Dakota Citation, a wind profiler, a ground-based microwave radiometer and NEXRAD and NWS soundings from Rapid City. This project was part of a larger NASA-funded program called the Upper Missouri River Basin (UMRB) project that emphasizes coupled hydrologic modeling of Intermediate Scale Areas (ISA) in orographic terrain, the use of observations of differing temporal and spatial resolutions to assess ambient variability as well as model and budget uncertainties and sensitivities, intercomparison of sensors and the transferability of models from the Black Hills ISA to other ISAs. The project involved staff from SSSF and DFS and was overseen by project engineer Ned Chamberlain.