Laserfiche WebLink
EXECUTIVE SUMMARY <br />1.0 SPECTRA II PLANS, OBJECTIVES AND RESOURCES <br /> In 2003 the Texas Department of Licensing & Regulation (TDLR) was awarded a grant from the U. S. <br />Bureau of Reclamation to participate in a collaborative effort known as the Weather Damage Modification <br />SP <br />Program (WDMP). The research, which was to be supported by the grant was known as the outhern lains <br />ECTRASPECTRA <br />xperiment in loud-seeding of hunderstorms for ainugmentation (), was to evaluate the <br />physical mechanisms in the atmosphere, particularly within convective cloud towers leading to losses from hail <br />and drought and to identify and administer appropriate cloud seeding materials that might mitigate these losses. <br /> The original plan called for the research to be conducted in two phases in the Texas-Oklahoma portion <br />of the southern U. S. Great Plains region during the spring and summer of2004. Unforeseen delays in the bid <br />solicitation process allowed only the initial phase of the research to be accomplished during the late summer of <br />2004. This effort, which came to be known as SPECTRA I, focused on the documentation of the size <br />distributions of cloud condensation nuclei (CCN) throughout Texas. The results of this effort are reported under <br />separate cover. <br /> SPECTRA II focused primarily on the effect of cloud-base hygroscopic salt-powder seeding on cloud <br />processes, especially droplet coalescence, and precipitation. It was noted at the outset that SPECTRA II might <br />also yield some significant new insight into the impact that seeding has on convective storms having the <br />potential to produce hail. It is conceivable that hygroscopic seeding will transform continental clouds into those <br />that have a more maritime microphysical structure, characterized by an active coalescence process with early <br />glaciation and increased rainwater. Because maritime clouds rarely produce much hail, the transformation of <br />continental clouds having hail potential into more maritime clouds might ultimately lead to the reduction of <br />hail. <br />To attain the fundamental purpose of SPECTRA II, specific objectives were pursued: <br />(1) To disperse hygroscopic material (finely milled salts) at cloud baseinto the updraft regions of <br />growing convective towers and, then, to observe and document cloud behavior in response to the <br />seeding using ground-based radar and cloud-physics data obtained with a “chase” aircraft <br />especially outfitted for that purpose; the treated cloud volumes were identified by detecting <br />sulfur hexafluoride (SF) gas, which was released with the salt-powder nucleant; <br />6 <br />(2) To study the growth and decay of convective storms in west central Oklahoma using advanced <br />imaging processing and advanced storm identification algorithms as well as multiple sensor <br />high-resolution observational data; <br />(3) To study and document seeding signatures in convective towers using glaciogenic materials <br />dispensed from cloud base at one, or more, rain enhancement project areas in south Texas. <br /> SPECTRA II was completed during May and June 2005 and is the focus of this Final Report. Although <br />all objectives were pursued in SPECTRA II, the focus here is on Objective 1. Time, budgetary and monetary <br />constraints did not permit meaningful pursuit of Objective 3. Objective 2 will be addressed by the Oklahoma <br />research scientists in a separate report. <br />4 <br />