Secondary Seeding as a Means of Propagating Seeding Effects in Space and Time


  • William L Woodley Woodley Weather Consultants Littleton, Colorado
  • Daniel Rosenfeld Hebrew University of Jerusalem Jerusalem, Israel


Secondary seeding, whereby unseeded clouds ingest ice particles from clouds that earlier had received direct glaciogenic (e.g., silver iodide) treatment, is hypothesized to be a possible additional mechanism for the propagation of seeding effects in space and for time. The ingested ice particles, after experiencing some growth in the donor cloud, act to glaciate the receptor cloud during its active growth phase and provide it precipitation embryos. These embryos give the new cloud a head-start on precipitation development as they grow further as graupel to precipitation size in the updraft laden with high quantities of supercooled cloud water. This enhancement of precipitation-forming processes is postulated to be strongest in microphysically continental clouds in which natural and seeding-induced primary glaciation and hydrometeor growth are slow. A case study is presented to illustrate these processes.






Scientific Papers