Simultaneous Operational AgI and Hygroscopic Flare Seeding in Texas: Rationale and Results

Authors

  • William L Woodley Woodley Weather Consultants Littleton, Colorado
  • Daniel Rosenfeld Hebrew University of Jerusalem Jerusalem, Israel

Abstract

A case study on 11 August 1996 involved simultaneous operational seeding of clouds to the W and SW of San Angelo, Texas, with hygroscopic flares at cloud base (T = 16°) and with ejectable AgI flares near cloud top (T = -8°C). Twenty-three hygroscopic flares were expended over 99 min while 95 AgI flares were expended over 96 min in the same area of clouds. The rationale for these dual seedings is discussed. This case was evaluated with San Angelo, Texas, NEXRAD radar data by calculating the lifetime properties of the seeded and non-seeded cells. This included the derivation of echo height vs. rainfall relationships. No cloud physics data were available. Although some of the seeded clouds produced heavy rainfall, there were a few unseeded clouds within range of the radar that produced comparable rainfall amounts. Thus, the data do not permit an unequivocal assessmentof the effects of dual simultaneous hygroscopic and silver iodide seeding on this day.

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Scientific Papers