Laserfiche WebLink
<br />1. Introduction <br /> <br />Since the discoveries of Schaefer (1946) and Vonnegut (1947) there have <br /> <br />been a number of experime~ts focused on determining the effects of seeding <br /> <br />clouds. One approach has been to directly measure the effects using <br /> <br />instr~~ented aircraf~, radar, and detailed surface measurements (Leonov and <br /> <br />Perelet, 1967; Leskov, 1974; weic~T1an, 1974; Hobbs, 1975; Super and Heimbach, <br /> <br />,- <br />1988; Super and Boe, 1988).;Since 1976 the Sierra Cooperative Pilot Project <br />L.., <br /> <br />(sepp) has conducted research in the central Sierra Nevada of California to <br /> <br />"j\ <br />',j y { <br />J\,.,rt1 v <br />/ <br /> <br />obtain physical evidence to quantify the effects of seeding, and to develop an <br /> <br />appropriate seeding technology for the Sierra Nevada. The SCPP has been <br /> <br />surr.~arized by Reynolds and ~er.nis <br /> <br />(1986). Heggli and Rauber (1988) gave an:? .y- <br /> <br />affect the Sierra 8evada, while Harwitz S f' ~'7r <br /> <br />(1987a, 1987b) has described the deep orographic storms which affect the area. <br /> <br />overview of the storm types which <br />oJ . <br /> <br />Huggins and Rodi (1985) presented results from seeding experiments on post <br /> <br />frontal cumulus, and Deshler et al. (1989) presented results from experiments <br /> <br />...., <br />on orographic clouds:) The c:oud types studied during this project have <br />~ <br />centered on post-frontal cumulus, stratus, and stratoc~~ulus which form over <br /> <br />the Sier~a Nevad~Cloud seeding was done from aircraft using primarily <br />..- <br /> <br />either dry ice or droppable pyrotechnic flares containing AgI. Stewart and <br /> <br />Marwitz (1982) compare results of seeding stratifrom clouds with these seeding <br /> <br />agents. These seeding ~aterials were chosen because, according to clear air <br /> <br />tes~s over a lake, they would produce a vertical curtain of ice crystals which <br /> <br />exte~ded 700 m below the seecer aircrafc. Such an effect was felt to be more <br /> <br />easily found and tracked ~i~h a research aircraft than, for exareple, a line <br /> <br />source of Ag! burned in acetone. The results with these materials, however, <br /> <br />were limited and lead in the final year of the project to the experimental use <br /> <br />F- ._''--':') <br /> <br />of AgIVas a line source. <br /> <br />., <br />