Project Mountain Valley Sunshine Progress in Science and Technology

Abstract

In order to improve the cloud seeding reaction, the basic processes in cloud microphysics and dynamics were critically examined. The disadvantage of the large temperature dependence in heterogeneous ice nucleation, as well as the advantage of there being almost no temperature dependence of strong coolants in homogeneous ice nucleation, was pointed out. A new horizontal seeding method using liquid carbon dioxide has been devised to maximize the effects of seeding, and simple devices for airborne and ground mobile applications were developed and tested in supercooled fogs and low-lying stratus clouds. Seeding tests revealed the development of vertical motions of the seeded plume and associated wind, the effective mixing of the plume with the surrounding supercooled fog and cloud volume, the resultant development of large crystals and their fall, the enlargement of the initial opening, the associated snowfall and its effects on traffic, and the accompanying optical effects. The developed ground mobile fog seeding method was found to be practical. A fundamental feedback reaction of the seeded plume at or near the overlying stabilization zone, which we call FILAS (falling-growth induced lateral air spreading), has been identified as an effective mechanism to cause precipitation in a large fog and cloud volume. Cellular motions and accompanying pseudoadiabatic lapse rates were confirmed in the fog and cloud.