General and Special Hypothesis for Winter Orographic Cloud Seeding

Authors

  • C. J. Todd Department of the Interior Water and Power Resources Service Office of Atmospheric Resources Management
  • W. E. Howell Department of the Interior Water and Power Resources Service Office of Atmospheric Resources Management

Abstract

Our purpose is to improve the rate at which evidence of the effect of cloud seeding under various weather conditions can be compiled. To do this, we have used the compiled data on individual experimental events for six winter orographic cloud-seeding experiments, and we have constructed a scheme based on our understanding of physical principles of precipitation that leads, for each event, to an expectation of its outcome for seeded and unseeded conditions respectively. Matching of the varying expectations to diverse outcomes is expected to accumulate evidence faster than if expectations are undifferentiated.

The construct of physical principles constitutes what we call a general hypothesis. It is a tentative statement of how we think icenuclei cloud seedinq works under the range of weather conditions encompassed in our data set. For each specific experimental event, the input data operate on the general hypothesis to convert it into a special hypothesis, a specific statement of expected outcome for the seeded, respectively unseeded, conditions of that particular event.

The expected outcome of seeding is under some weather conditions an increase in precipitation, under other conditions a decrease, and sometimes no change. We will have succeeded in our aim if the special expectations track the direction and magnitude of the seeding effect more closely than a less particularized hypothesis could do. At this point, we leave it as an exercise for the statistician to convert the improved expectations into an improved protocol for testing the qeneral hypothesis and its special subsets.

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Scientific Papers