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Last modified
7/28/2009 2:28:42 PM
Creation date
10/1/2006 2:16:21 PM
Metadata
Fields
Template:
Weather Modification
Applicant
North American Weather Consultants
Sponsor Name
Upper Colorado River Commission
Project Name
The Potential Use of Winter Cloud Seeding Programs to Augment the Flow of the Colorado River
Title
The Potential Use of Winter Cloud Seeding Programs to Augment the Flow of the Colorado River
Prepared For
Upper Colorado River Commission
Prepared By
Don Griffith, NAWC
Date
3/1/2006
Weather Modification - Doc Type
Report
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<br />naturally-occurring 1l\~ which common(..... have thresholds closer to .150C The chemical <br />formulations of Agl seeding llgent.\. may be mod~fiedfurther, so that the resulting IN <br />fUf1(.tion at e\'en warmer temperatures (DeA-folt 1991. Garvey 1975). <br /> <br />Drr Ice <br />The direct (Teation of cloud ice particles by di.~lJensinK ,b:r ice (COj pellets into <br />the cloud is another glaciogenk seeding technique u.hich modifies the nalllral ice <br />formation proct!ss by rapid(r trlm'ij(Jrming nearby mpor and cloud droplets into ice <br />(Schaefer 19-16, I/olroyd etal. 1978. VonnexUl 1981), <br />Compared with sill'er iodide complexes, Ihis sy,')/em has an admntllge in that il <br />makes use ofll natural subslllnce (frozen carbon dioxide. CO;!. which suhlimes at .780C <br />at 1,000 IIPa). 1I0wel'er. effeclive delivery oflhe C01 requires the lise ofaircrl~ft. The <br />CO.. is also dij}kulllo slore, as sublimalion (and fherefilre loss) is conlinuolH. It is <br />Ill/common for dry ice 10 be Ihe on(..... seeding agenlused in a projecI: if is sometimes used <br />in conjunction wilh Agl seeding. <br /> <br />Lietaid ProplIne <br /> <br />Liquid propane is afree=ing agent milch lih' lby ice. II produces almost the same <br />number of cryslals per gram as does CO;! (Kumai 1982). It Cllnnot be dispemedjrom <br />airaaji because if i.~ aJlammable substann.'. /-I{)\\'(.'l'er. il call be di.\jwnsedfrom the <br />ground if released al del'lltions which are frequently within supercooled cloul/\'. The <br />Uniled .)'tates Air Force has used liquid propane dispen.w:d from growul-based siles 10 <br />dear .\'IIpercooledfiJg al miJitmyairportsfiJr over thirty years. <br /> <br />Propane seeding \vas tcstcd as a cloud secding agent on a wintcr research program <br />conducted in California for .....inter snowpaek cnhancemcnt through the dcvelopment of a remotely <br />operated ground-based dispenser (Rcynolds 1991. 1992). Liquid propane seeding cxpcriments <br />were also conducted on the UtahINOAA Atmospheric Modification Project (Super. 1999). The <br />intcrest in propane sceding is due primnrily to thc fact that propanc seeding may be elTcctive at in- <br />cloud temperatures near _20 C comparcd to the effectiveness of silver iodide beginning at <br />temperatures of approximately .5oC. Research in some mountainous arcas ofthc \\cst in <br />wintertime indicate that there appears to be rather frequent occurrences of supercooled liquid water <br />at tc:mpcratures between 00 and -So C (Super. 1999). Sincc supercooled liquid watcr droplcts are <br />thc target of cloud seeding the hope is that seeding with liquid propane could expand the window <br />of seeding opportunities in tenns of in.c1oud temperatures. A rccent randomized research <br />experiment was conducted on the central Wasatch Plateau of Utah testing this agent's possible <br />usefulness in \\ intcr timc cloud seeding programs (Super and Heimbach. 2005). Results of thc <br />randomized treatments indicate seeding increases over a small arca during some stonn periods with <br />liquid propane. An update to the ASCE Manual 81 (ASCE. 1995) titled "Guidelines for Cloud <br />Seeding to Augment Precipitation" (due to be published early 2006) contains a recommendation <br />that future experimentation needs to be conducted using liquid propane seeding over a fixed targct <br />arca to dcmonstrate that increases are occurring over substantial timc pcriods. As a consequence. <br />propane seeding is not recommendcd for use in the near term as all operational cloud seeding <br />agcnt on the potential Colorado River Basin programs. It is recommended that a multi-war <br />r;scarch program be conducted to dctennine the elfecti....eness of propane seeding in ge'nerating <br />
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