Testing of Dynamic Cold-cloud Seeding Concepts in Thailand Part II: Results of Analyses


  • Daniel Rosenfeld Department of Atmospheric Sciences Hebrew University of Jerusalem
  • William L Woodley Woodley Weather Consultants Littleton, CO
  • Warawut Khantiyanan Royal Rainmaking Research & Development Institute Bangkok, Thailand
  • Wathana Sukarnjanaset Royal Rainmaking Research & Development Institute Bangkok, Thailand
  • Prinya Sudhikoses Royal Rainmaking Research & Development Institute Bangkok, Thailand
  • Ronit Nirel Department of Statistics Hebrew University of Jerusalem


Part Il provides the results of analyses of Thailand’s randomized, exploratory, cold-cloud, seeding effort. The sample is small and caution should be exercised in interpreting the results of these analyses. A total of 151 convective cells (87 seeded and 64 nonseeded) have been identified within the experimental units and their properties computed through analysis of three-dimensional, volume-scan, S-band radar data using cell tracking software. The results indicate that AgI seedimg may have increased the maximum cell areas by 25%, durations by 14% and rain volumes by 69%. Little effect is indicated on maximum cell heights, which may be due in part to underestimation of the glaciated tops of AgI-treated clouds by the S-band radar. Additionally, within the height range of 7 to 11 km, seeded cells of a given maximum echo top produced more rain volume than unseeded cells of the same height. None of the results has strong statistical support. Partitioning by cloud base temperature increased the apparent effect of seeding to 71%, 33% and 125% for cell areas, durations and rain volumes, respectively, within the warm base (T > 16 degrees C) partition. The apparent effect on maximum cell height is on the order of +6%. The results for the small sample (i.e., 7 Seed and 7 NS) of experimental units also show more S than NS rainfall. All results are comparable to what has been reported by the first two authors for a similar program in Texas, and are discussed in the context of the conceptual model guiding both experiments. This work was conducted under a contract with the Bureau of Reclamation part of a program sponsored by the U.S. Agency for International Development to upgrade Thailand’s weather modification capability.




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