Summary & Purpose

"Glaciogenic cloud seeding with silver iodide (AgI) has been used to enhance precipitation for over 60 years. Assessments of AgI impact and dispersion are often quantified using atmospheric processes models with impact assessed by comparing models with and without the inclusion of cloud seeding modules. However, there is inherent uncertainty in these models. Quantifying AgI distribution in the snowpack following cloud seeding can both validate and improve model performance. The purpose of this study is to demonstrate the capacity to document the dispersion of AgI by measuring silver (Ag) enrichments in snow. This study develops clean field and laboratory procedures to detect trace seeding signatures in alpine snowpack. Unique laboratory layout and protocols are employed to reduce contamination potential within a traditional ICP-MS laboratory setting (not housed in a Class 100 Clean Room). Using these methods, we sample a series of snow profiles within the target area of active cloud seeding in the central mountains of Idaho. The results demonstrate the ability of the new methods to reproduce distinct elevated Ag concentrations over a small scale (0.25 km2) and at the basin (2,400 km2) scale. The trace chemical analysis of snow samples from eight snow pits over an area of 0.25 km2 and six sites separated up to 65 km (basin scale) identify potential seeding signatures from two seeded storms. A localized enrichment factor was used to identify and replicate this seeding signature at all six sites within the basin. This enrichment factor can delineate a seeding signature at sites far downwind from AgI sources, where Ag concentrations are only 1-3 parts per trillion above background levels. The localized enrichment factors at all six sites contain chemical snow profiles generally corresponding to peak Ag concentrations and known cloud seeding events. "

Date of Publication or Submission



Funding Citation

Heritage Environmental Consultants (sub-contracted via Idaho Power Company)

Single Dataset or Series?


Data Format

*.xlsx, *.doc

Time Period

Snow samples collected between Nov-Mar in two winter seasons: 2014-2015, 2015-2016

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Confidential Client Information 4.09. (a) Each party has certain documents, data, information, and methodologies that are confidential and proprietary to that party (“Confidential Information”). During the term of this Agreement, either party may, as the “Disclosing Party,” disclose its Confidential Information to the other party (the “Recipient”), in writing, visually, or orally; provided, however, the Disclosing Party shall, at the time of disclosure, clearly identify to the Recipient what the Disclosing Party considers to be Confidential Information. Recipient shall receive and use the Confidential Information for the sole purpose of the performance of this Agreement, and for no other purpose (except as may be specifically authorized by the Disclosing Party, in writing). Recipient agrees not to make use of the Confidential Information except for the performance of the Description of Services and agrees not to disclose the Confidential Information to any third party or parties, unless required by law, without the prior written consent of the Disclosing Party. (b) Recipient shall use its reasonable best efforts to preserve the confidentiality of the Confidential Information (using the same or similar protections as it would as if the Confidential Information were Recipient’s own, and in any event, not less than reasonable care). Recipient shall obligate its affiliates with access to any portion of the Confidential Information to protect the proprietary nature of the Confidential Information. (c) “Confidential Information” shall not include, and Recipient shall have no obligation to refrain from disclosing or using, information which: is generally available to the public at the time of this Agreement; becomes part of the public domain or publicly known or available by publication or otherwise, not through any unauthorized act or omission of Recipient; is lawfully disclosed to the Recipient by third parties without breaching any obligation of non--‐use or confidentiality; has been independently developed by persons in Recipient’s employ or otherwise who have no contact with Confidential Information, as proven with written records. (d) In the event that Recipient is required by law to disclose Confidential Information, it will promptly notify the Disclosing Party, and the Disclosing Party may, at its sole discretion and expense, initiate legal action to prevent, limit or condition such disclosure. (e) Notwithstanding any other provision of this Agreement, a party may retain one copy of the other party’s Confidential Information in its confidential files, for the sole purpose of establishing compliance with the terms hereof. (f) Contractor further agrees that all Contractor's client files, records, documents, and similar items relating to Contractor's clients, including copies, reproductions, and facsimiles of such items, whether prepared by Subcontractor or others, are and shall remain exclusively the property of Contractor.

Use Restrictions

Users are free to share, copy, distribute and use the dataset; to create or produce works from the dataset; to adapt, modify, transform and build upon the dataset as long as the user attributes any public use of the dataset, or works produced from the dataset, referencing the author(s) and DOI link. For any use or redistribution of the dataset, or works produced from it, the user must make clear to others the license of the dataset and keep intact any notices on the original dataset.

Available for download on Wednesday, April 18, 2018


Article Location