Evaluation of the South Dakota weather modification program


  • Richard Leblang
  • Jackson Pellett


Weather Modification Operations


Evaluation of the past four years of the state sponsored South  Dakota weather modification program was performed through the use of computer gridded monthly rainfall data, daily precipitation data, and crop-hail insurance data. Results indicate  that over the four years of seeding the seeded counties  received, overall, 6.7% more rainfall than would have been  expected based on unseeded county precipitation. Rank testing  with 31 years of gridded historical data give a significance level  of 1.5% to the results. Analysis of daily rainfall data shows both  a 5.4% increase in rainfall frequency and a 2.8% increase in  rainfall intensity in the seeded counties. In addition to the rainfall results, crop-hail insurance data shows that the seeded  counties received less hail damage than the unseeded counties  with significance at the 3.4% level. It is postulated that the high  significance levels of the findings are a result of the great  number of clouds treated and the large size of the regions  participating in the program.




Technical Notes and Correspondence