Progress in planned weather modification research: 1991–1994

This quadrennial marked progress in understanding basic cloud processes under natural and seeded conditions, development of conceptual models, and application of advanced computer cloud models and instrumentation. Conceptual models were revised so that effects on the scale of cloud particles, precipitation processes, and cloud development no longer are artificially distinguished from one another; for example hail suppression and precipitation enhancements are now viewed as possible concurrent effects from seeding. Transport and dispersion studies using tracers have begun to show the path of seeding material and have allowed documentation of physical effects. Application of two‐ and three‐dimensional computer cloud models have helped to explain some results, to guide field operations, and to suggest further work. Instrumentation such as microwave radiometers and lidars have been used to document the spatial and temporal structure of supercooled liquid water.