Laserfiche WebLink
<br />In view of the accomplishments of the Florida and Texas cold cloud dynamic seeding <br />programs, the techniques and approaches were transferred to the Thai situation through <br />exploratory experiments that focused initially on convective cells. These Thai experiments <br />were patterned closely after those that are continuing in Texas. The Texas design has <br />worked extremely well in the field since its improvement in 1987, and the results of the <br />program to date have been most gratifying (Rosenfeld and Woodley, 1989; 1993). Many <br />reasons exist, therefore, to start in Thailand with this proven design. <br /> <br />The beginning point in the AARRP rain enhancement program, therefore, was the <br />documentation of the primary seeding effect on the actually seeded entities, namely, the <br />individual convective cells. <br /> <br />The question addressed with this approach was: <br /> <br />"Does the glacio genic seeding of suitable supercooled convective towers for the <br />production of dynamic effects produce greater echo top-heights, areas, durations, and <br />rainfalls in the cells in which these towers reside?" <br /> <br />If the answer to this question proved to be "yes," the way would be clear to proceed to the <br />next step in developing a cold cloud, dynamic seeding, rain enhancement technology for <br />Thailand. If the answer proved to be "no," then no basis would exist for proceeding further <br />with this particular seeding approach. Confirming the potential in a short duration <br />experiment on single convective cells was felt to be necessary before considerable time, effort, <br />and resources were invested in a multi-year test of this seeding approach in enhancing area- <br />wide rainfall. <br /> <br />2.4.2 Design of the Thai cold cloud. seeding and its implementation <br /> <br />The Thai experiments were carried out in accordance with the Design Document and AARRP <br />Operations Plans by Woodley et al. (Jl991). In every case, the experimental unit was the <br />small, multiple-cell convective system within a circle having a radius of 25 kilometers and <br />centered at the location of the convective cell which qualified the unit for treatment. The <br />treatment decisions were randomized on a unit-by-unit basis, and all suitable convective cells <br />within the unit received the same treatment-AgI in the case of an S (seed) decision or <br />simulated AgI in the case of an NS (no seed) decision. <br /> <br />In the Thai design, therefore, the treatment units were the convective cells which contained <br />cloud towers that met the liquid water and updraft requirements. The cell receives the <br />treatment, and any effect of seeding should manifest itself first on this scale before it is seen <br />in the experimental unit that contains the cells. Additional information on the design ofthe <br />Thai exploratory experiments is provided in appendix B. <br /> <br />During the randomized experimentation, suitable supercooled convective cloud towers within <br />the convective cells received either simulated AgI treatment or actual AgI treatment near <br />their tops (typical top heights of 6.0 to 7.0 kilometers and top temperatures of -7 to -9 DC). <br />The seeding devices were dropable flares that produced 20 grams of AgI smoke during their <br />1-kilometer free-fall through the upper portion of the cloud. Between 1 and 10 flares <br />normally were ejected during a seeding pass. The flare ejection button was pressed about <br />every second while the cloud liquid water reading was greater than 0.5 gram per cubic meter <br />and the aircraft was in updraft (the 1.0-gram-per-cubic-meter and 5-meter-per-secondc <br />7 <br />