Search Results

You are looking at 11 - 13 of 13 items for

  • Author or Editor: Arlin B. Super x
  • Refine by Access: All Content x
Clear All Modify Search
Edmond W. Holroyd III, Arlin B. Super, and Bernard A. Silverman

Abstract

Dry ice is shown to be an attractive agent for on-top seeding of convective clouds. A modest payload of small dry ice pellets can effectively seed dozens of clouds, depending on cloud volumes encountered and crystal concentrations desired. A dry ice pellet size of about 7 mm diameter is suggested for efficient use of seeding agent when dropped from the −10°C level.

Supercooled convective clouds that were seeded on-top with dry ice were investigated to determine empirical nucleation effectiveness values. The clouds were repeatedly penetrated to measure the resulting ice crystal concentrations. The experiments gave conservative effectiveness values of 2 to 5 × 1011 crystals per gram of dry ice, but with possible error bars extending an order of magnitude to each side of those values. A well-documented experiment giving effectiveness values twice as large is discussed in detail.

Full access
Arlin B. Super, Bruce A. Boe, Edmond W. Holroyd III, and James A. Heimbach Jr.

Abstract

A series of winter orographic cloud seeding experiments is described in which the seeding agent and associated changes in cloud microphysics are monitored to within 300 m of the target areas (Montana and Colorado), and at the surface (Colorado only). This, the first paper in a three-part series, discusses the underlying physical hypothesis and experimental approach, and describes in detail the instrumentation used. The results of the physical evaluations, presented in Parts II and III, show that marked microphysical changes were caused by both ground-based and aircraft seeding with silver iodide.

Full access
Paul L. Smith, Arnett S. Dennis, Bernard A. Silverman, Arlin B. Super, Edmond W. Holroyd III, William A. Cooper, Paul W. Mielke Jr., Kenneth J. Berry, Harold D. Orville, and James R. Miller Jr.

Abstract

The design and conduct of HIPLEX-1, a randomized seeding experiment carried out on small cumulus congestus clouds in eastern Montana, are outlined. The seeding agent was dry ice, introduced in an effort to produce microphysical effects, especially the earlier formation of precipitation in the seeded clouds. The earlier formation was expected to increase both the probability and the amount of precipitation from those small clouds with short lifetimes. The experimental unit selection procedure, treatment and randomization procedures, the physical hypothesis, measurement procedures and the response variables defined for the experiment are discussed. Procedures used to calculate the response variables from aircraft and radar measurements are summarized and the values of those variables for the 20 HIPLEX-1 test cases from 1979 and 1980 are tabulated.

Full access