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<br />',,- <br /> <br />e <br /> <br />- <br /> <br />- <br /> <br />and can be associ ated wi th upper-1 eve1 trough passages. Convect ive <br />elements within these bands move along the band's length. Subsidence <br />ahead and behind these bands is generally evident. The bands usually <br />exist for long periods and move up and over the Sierra barrier. <br /> <br />3. Cells and multicells exhibit the best potential for seeding of all <br />cloud types examined thus far. They ~~enera11y occur postfronta11y but <br />can exist anywhere in an unstable airmass where surface heating is <br />strong. Cell lifetime is quite variable in the Sierra Nevada, lasting <br />from less than one-half hour to more than 3 hours. There are indica- <br />tions that seeding cells, very early in their lifetimes, may be the only <br />effective means for enhancing precipitation.' However, if the cell <br />continues for some time after initial seeding, it may become a target <br />for additional treatment. <br /> <br />4. Rad ar data an a 1 ys is showed that c: loud street s are a r ather common <br />occurrence in Sierra storms. Previous analysis had identified these <br />features as stationary bands because of the 1 ack of mot ion perpendicu1 ar <br />to the band ax is and the embedded ce:ll s mov i ng along that ax is. It <br />appeared that the source for some of these cloud streets is a topo- <br />graphical point. Precipitation effects from these features can extend <br />150 km downwind from the source region, and it appears that some <br />enhancement potential may exist in them. <br /> <br />5. It seems that a Ha1lett-Mossop or similar ice multiplication process <br />was a dominant process at times in the Sierra clouds discussed above. <br /> <br />6. Calibration seeding experiments, using high and low dry ice rates, <br />10 lb/min and 1 1b/min, high AgI (silver iodide) rates, 20 f1ares/min, <br /> <br />1-7 <br />