The North Dakota Tracer Experiment planned for the summer of 1993 will focus on continued study of transport, dispersion, ice initiation, and hail embryo development processes in active convective clouds and storms. The scientific goal will be to increase understanding of these processes in natural and seeded clouds, and their relation to the subsequent development of precipitation (including hail). The primary experimental techniques will employ tracer materials released from aircraft, including gaseous SF6, radar chaff, and fluorescent beads (for hailstone-embryo studies). The 1993 project will emphasize pulsed releases (typical duration 30 s) of the tracer materials to facilitate studying the time evolution of transport and dispersion processes and of the hydrometeors. Releases will be made in feeder clouds whenever opportunities arise, to study transport between feeder and main cell, and in other cloud types as available. The South Dakota School of Mines and Technology T-28 and University of North Dakota Citation will sample the clouds for SF6 as well as for kinematic and microphysical characteristics. C-band Doppler radar will provide one Doppler surveillance of the origin of precipitation, and determine whether the storms have feeder cell characteristics. One mobile CLASS system will provide timely soundings of the local environment.
