WMOD00270 - Laserfiche WebLink

Home Browse Search

west central Oklahoma. A few missions to address the secondary objective of documenting seeding signatures of clouds seeded at base with glaciogenic materials were based at the airport in Pleasanton, Texas, later in the summer. These missions were conducted within the multi-county “target” areas of the South Texas Weather Modification Association (based in Pleasanton) and the Southwest Texas Rain Enhancement Association (based in Carrizo Springs). The co-Principal Investigators for SPECTRA Phase II (SPECTRA II)were Dr. William L. Woodley (President, Woodley Weather Consultants) and Prof. Daniel Rosenfeld (Hebrew University of Jerusalem, in Jerusalem, Israel), who have composed the primary research team in Texas for the past 20 years. Duncan Axisa of the SOAR Program served as the primary instrumentation technician and as flight scientist on selected flights. Dr. Kenneth Howard, of the National Severe Storms Laboratory, and Nathan Kuhnert, of the Oklahoma Water Resources Board had oversight responsibilities for the work performed during and after the field exercises in research facilities in Norman OK. The piloting of the research aircraft was shared by Dr. David Prentice and Mr. Gary Walker, while the base seeder was flown by Mike Hanneman. The TDLR’s George Bomar provided administrative and technical oversight for the effort. 2.0 OPERATIONAL OUTCOME The period of research was to extend from May 8, 2005 until about June 10, 2005, or before if the allocated number of hours on the two aircraft had been expended. As of Sunday, June 5, 2005, the first phase of the field activities of SPECTRA-II in 2005, focusing on the effect of hygroscopic salt-powder seeding on cloud processes, came to an end. The weather during the 35 days (1 May through 4 June 2005)of the experiment was a disappointment in that there were only 7 days with convection suitable for the salt experiments. There were 20 days of suppressed convection and 6 days of disturbed conditions with rain and low ceilings. Additionally, there apparently was suitable convection on 2 days, but their cloud bases exceeded 10,000 ft and could not be reached by the salt seeder. On 7 days it was necessary to deploy the salt seeder to other areas in order to reach suitable convection. There was one deployment of project personnel and two aircraft (Cheyenne and Ag Wagon) to Norman, Oklahoma with the intention of conducting a salt seeding experiment within range of the NSSL dual polarization radar. Unfortunately, suitable clouds never materialized and it wasnot possible to take advantage of this unique opportunity. During this period it was not possible to deploy to Pleasanton, Texas, for the glaciogenic studies because of the primary commitment in West Texas to the salt seeding experiments. A deployment came later in the summer with one unsuitable base glaciogenic seeding event that is not addressed here.. During the 35 days of operation in May and June 2005 there were 16 flight days and 34 flights, including 11 research and 2 ferry flights by the Cheyenne cloud physics aircraft, 12 research and 2 ferry flights by the Cessna Ag Wagon salt seeder and 7 flights by the Comanche reconnaissance aircraft. There were 7 salt experiments with monitoring by the cloud physics aircraft. During these experiments the expenditures of sized salt and SF6 gas were 556.4 kg and 59.2 kg, respectively. The SF6 gas was detected by the SF6 detector on the cloud physics aircraft during portions of 4 of the 7 experiments and an apparent microphysical seeding signature was noted in the strongest updraft cases, especially on May 25 and 31, 2005. A substantial portion of project resources were used during the initial project period. The 40-hour allocation for flight of the base aircraft (Ag Wagon and Comanche) was used and a nearly 10 hour overage was paid for in Cheyenne flight hours on a 3:1 basis (i.e. 1 Cheyenne hour = 3 hours by the base aircraft. A net of about 18 Cheyenne flight hours remained for later use in SPECTRA-II. There were 1,372 kg of sized salt and 6