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<br />MS-230 (2-72) <br />Bureau of Reclamation <br />1. REPORT NO, <br /> <br /> <br />5. REPORT DATE <br /> <br />4. TITLE AND SUBTITLE <br /> <br />i Summary Report <br />Generalized Criteria for Seeding Winter <br />Orographic Clouds <br /> <br />March 1977 <br />6. PERFORMING ORGANIZATION CODE <br /> <br />7, AUTHOR(5) <br /> <br />8. PERFORMING ORGANIZATION <br />REPORT NO. <br /> <br />9, PERFORMING ORGANIZATION NAME AND ADDRESS <br /> <br />10, WORK UNIT NO, <br /> <br />Bureau of Reclamation <br /> <br />E&R Center <br /> <br />Denver Federal Center <br /> <br />Denver Colorado 80225 <br />12, SPONSORING AGENCY NAME AND ADDRESS <br /> <br />11. CONTRACT OR GRANT NO. <br /> <br />13, TYPE OF REPORT AND PERIOD <br />COVERED <br /> <br />Summary <br /> <br />14. SPONSORING AGENCY CODE <br /> <br />15. SUPPLEMENTARY NOTES <br /> <br />This report summarizes the I2l-page full report titled "Generalized <br />Criteria for Seeding Winter Orographic Clouds" ~ by Vardiman and Moore ~ <br />Sk ater Mono ra h No.1. <br />16, ABSTRACT <br />An a posteriori analysis is being conducted utilizing precipitation~ <br />rawinsonde~ and seeding generator data from seven randomized winter cloud- <br />seeding research projects conducted in orographic settings in the Rocky <br />Mountain West and on the Pacific Coast of the United States. Variables <br />are being developed and investigated 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 categories: <br />tiID2 available~ water available~ nuclei available~ and mixing available. <br />The analysis approach is to establish "windows'" under which positive <br />(increases) or negative (decreases) seeding effects would be obtained. Thus <br />fa.r~ the analysis shows that positive seeding effects occur alt the crest <br />under stable or unstable conditions when a "crest trajectory" is present~ <br />moderate-to-high cloud moisture ~s present ~ and the cloud top temperature <br />is between minus 10 and minus 30 C. Decreases occur at the crest for <br />unstable clouds with a "blow-over" trajectCJry. with low cloud moisture and <br />cloud top temperature colder than minus 30 C. The precipitation for upwind <br />and downwind regions of a barrier can also be increased or decreased <br />depending on stability. trajectory. cloud moisture. and cloud top tempera- <br />ture. Othe I' windows are dis cussed in the report. <br />17, KEY WORDS AND DOCUMENT ANALYSIS <br />a, DESCR IPTORS-- / cloud seedingl orographic clouds/ weather modification/ <br />precipitation augmentation/ cloud seeding criteria/ snow/ cloud physics/ <br />snowpack augmentation/ winter orographic clouds. <br /> <br />I <br />I <br /> <br />I <br />'I <br /> <br />b, IDENTIFIERS-- /Rocky ~1ountain Region/ Pacific Coast Region <br /> <br />c. COSATI Field/Group 04B <br /> <br />COWRR <br /> <br />0402.1 <br /> <br />18. DISTRIBUTION STATEMENT <br /> <br />Avaiiabie from the National Technical Information Service, Operations <br />Division, Springfield, Virginia 22/51, <br /> <br />19, SECURITY CLASS 21, NO, OF PAGES <br />(THIS REPORT) <br />UNCLASSIFIED <br />20, SECURITY CLASS 22. PRICE <br />(THIS PAGE) <br />UNCLASSIFIED <br />