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<br />~._~- <br />- <br /> <br />MS-230 (1-76) <br />Bureau of Reclamation <br /> <br />TECHNICAL REPORT STANDARD TITLE PAGE <br /> <br />sky~1rtoe\I ~fcinOgraPhr' ::;O'JERIIoMENT A:-t:.~S"ION ..c. .- <br /> 3. RECIPIENT'S CATALOG NO. <br /> Nn 1 <br /> 4. TITLE AND SUBTITLE S. REPORT DATE <br /> Generali zed Criteria for Seeding Winter July 1977 <br /> Orographic Clouds 6. PERFORMING ORGANIZATION CODE <br /> 7. AUTHOR(S) 8. PERFORMING ORGANIZATION <br /> Larry Vardiman and James A. Hoore REPORT NO. <br /> Skywater Honograph Report <br /> No. 1 <br /> 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. WORK UNIT NO. <br /> Engineering and Research Center <br /> Bureau of Reclamation 11. CONTRACT OR GRANT NO. <br /> Denver, Colorado <br /> 13. TYPE OF REPORT AND PERIOD <br />12. SPONSORING AGENCY NAME AND ADDRESS COVERED <br /> 14. SPONSORING AGENCY CODE <br />1S. SUPPLEMENTARY NOTES <br />16. ABSTRACT <br />An a posteriori analysis is being conducted utilizing precipitation, <br />rawinsonde, and seeding generator data from seven randomized winter cl oud- <br /> seeding research projects conducted in orographic settings in the Rocky <br />Mountain West and on the Pad fic Coast of the United States. Variables <br /> are being developed and invcstip,ated to establish generalized seedability <br /> criteria that are applicable under a variety of meteorological and topo- <br /> graphic conditions. The variables are divided into four general cate- <br /> gories: time available, water available, nuclei available, and mixing <br /> available. The analysis approach is to establish "wi ndows" under \"hi ch <br />positive (increases) or negative (decreases) seeding effects would be <br /> obtained. Thus far, the analysis ShO\'IS that positive seeding effects <br />occur at the crest under stable or unstable conditions when a "crest tra- <br /> jectory" is present, moderate-to-high cloud moisture is present, and the <br /> cloud top temperature is between minus 10 and minus 30 oc. Decreases <br />occur at the crest for unstable clouds with a "blow-over" trajectory, with <br /> low cloud moisture and cloud top temperature colder than minus 30 oc. 111C <br />precipi tation for upwind and downwind regions of a barrier can also be <br />increased or decreased depending on stability, t raj ectory , cloud moisture, <br />and cl oud top temperature. Other windows arc discussed in the report. <br />17. KEY WORDS AND DOCUMENT ANALYSIS <br />a. DESCRIPTORS-- / cloud seeding/ orographic clouds/ \"eather modi fication! <br />precipitation augmentation! cloud seeding criteria! snow! cloud physics! <br />snO\.,rpack augmentation! winter orographic clouds <br />b. IDENTIFIERS-- ! Rocky Hountain Region! Pacific Coast Region <br />c. COSATI Field/Group: 04B COWRR: 0402.1 <br />18. DISTRIBUTION STATEMENT 19. SECURITY CLASS 21. NO. OF PAGES <br />Available from the National Technical Information Service, Operations (TH IS RE pORT) 119 <br />Division. Springfield, Virginia 22/51. UNCLASSIFIED <br /> 20. SECURITY CLASS 22. PRICE <br /> (THIS PAGEl <br /> UNCLASSIFIED <br /> <br />~ <br />] <br />