Estimations of Downwind Cloud Seeding Effects in Utah

Authors

  • Mark E Solak North American Weather Consultants, Inc. Sandy, Utah
  • David P Yorty North American Weather Consultants, Inc. Sandy, Utah
  • Don A Griffith North American Weather Consultants, Inc. Sandy, Utah

Abstract

Estimations of effects on precipitation downwind of a long-standing operational snowpack augmentation project in Utah are made, using an adaptation of the historical target/control regression technique which has been used to estimate the seasonal effects over more than twenty seasons within the project’s target area. Target area analyses of December-March high elevation precipitation data for this project indicate an overall season-average increase of about 14%. Estimations of downwind effects are made for distance bands downwind as far as 150 miles. The downwind analyses indicate increases of similar magnitude to those for the target, expressed as percentages or ratio values, extending to about 100 miles downwind. Beyond 100 miles the ratio values decay, reaching 1.0 at about 125 miles. Expressed as average-depth precipitation amounts, the target area precipitation difference is about 1.4 inches of additional water, while the values within downwind distance bands range from 0.4 to 0.25 inches, reaching zero at about 125 miles.

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Technical Notes and Correspondence