Review of Persistence Effects of Silver Iodide Cloud Seeding
AbstractThis paper is concerned with persistence effects of cloud seeding for precipitation enhancement. Effects may last for hours or days. Persistence of cloud seeding effects means that this environmental technology may affect the microphysical structure of clouds and the development of precipitation for a significant amount of time after the seeding has been completed. According to Rottner, Brown, and Foehner (1975), persistence may complicate the evaluation of a cloud seeding experiment and reduce the perceived net effect of the seeding. The sensitivity of the experiment to the actual net effect may be reduced. Their work in Colorado and New Mexico demonstrated a smaller cloud seeding effect because of persistence. When no account was taken that cloud seeding material was incorectly present in the conrol period part of the time, the seed/no-seed conrast in precipitation and the effect of seeding were smaller. When the incorrectly seeded parts of the control period were reassigned to the target period, the contrast and the effect of seeding were greater. There has been considerable post-analysis of precipitation data associated with cloud seeding experiments in Australia by Bigg and colleagues in a search for persistence effects. Unfortunately, there apperars to be a flaw in some (but not all) of the analysis which exaggerates the time span (siad to be up to two weeks) of the effects. Artificial ice nuclei are generated by the cloud seeding aparatus and are injected in various ways into a cloud to increase precipitation. The surmised connection between higher nucleus concentrations and increased precipitation suggests that measuring and examining ice nucleus concentrations for a period of perhaps a few days after seeding may be worthwhle in a search for persistence. Bigg and others have suggested that some silver iodide ice nuclei released in cloud seeding may be carried, presumably with precipitation, to the surface. There the nuclei are believed to stimulate chemical reactions, possibly on plants, that create products that are emitted into the atmosphere to function as a persistent ice nuclei. An alternative scenario is that the deposited slver iodide modifies or otherwise causes bacteria on the plants to loft into the atmosphere and also act as persistence ice nuclei.
Authors that submit papers for publication agree to the Journal’s copyright and publication terms. Authors retain copyright and grant the journal right of first publication with the work simultaneously licensed under a Creative Commons Attribution License that allows others to share the work with an acknowledgement of the manuscript’s authorship and initial publication in Journal of Weather Modification. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal’s published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgement of its initial publication in the Journal of Weather Modification. Authors are permitted to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process to encourage productive exchanges and greater citation of the published article.
Articles are published online using restricted access for the first year. After the first year, articles are made freely available online. Immediate open access for an article may be obtained by the author paying an open access fee which is in addition to the normal page changes. Authors are expected to honor a page charge in order to support publication and distribution of the journal. After the author approves the gallery formatted version for publication, the Weather Modification Association’s Secretary will invoice the corresponding author for the page charges and payment is due within 30 days.