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<br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />t <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br />. <br /> <br /> <br />.M102 <br /> <br />..ll <br /> <br />~-l <br />."10' .e;.U67 <br />'-1 <br />Son Luis Obispo Coun/y - --, <br /> <br />E0442 <br />. <br /> <br />.AU <br /> <br />..'1 <br /> <br />.AZ9 <br /> <br />. .S() <br /> <br />.M104 <br /> <br />..'1 <br /> <br />~~ <br /> <br />..46 I <br />~"' <br /> <br />.t:"$Z <br /> <br />...u <br /> <br />et:4144 <br /> <br />i <br />I <br />--- .. ..----t <br /> <br />"""' <br />"" ."41 <br />,/ - <br />.,U7..__..-4...4 "- <br />.- esass ............. .,z;:. ' e";)5 <br />SANTA MARIA '-... I <br />.tn... ""--.J <br />.sas6 ...20 .....5 .... ~..", <br /> <br />eszo.Sanlo 801'/)01'0 County <br />.Ul no...lU4 .U3I <br />· .$202 .~6 e Nil <br /> <br />.y~o. <br /> <br />., <br /> <br />e.48 <br /> <br />.....74 <br /> <br />.'1230 .....5.... <br />.'1'67. . e . <br />V.,, <br /> <br />.'1'" 'It: <br /> <br />Figure 2. Precipitation gauges used in the evaluation of the Santa Barbara II experiment <br />(from Thompson et aL 1975). <br /> <br />Contours of the ratios of the average seeded band precipitation to the not seeded band <br />precipitation are plotted in Figure 3. Ratios over 1.0 are common in this figure; a ratio of 1.50 <br />indicates a 50 percent increase in precipitation. The high ratios in Southwestern Kern County are <br />not significant in terms of amounts of additional rainfall since the convective bands (both seeded <br />and not seeded) rapidly lose intensity as they enter the San Joaquin Valley. In other words, a <br />high percentage applied to a low base does not yield much additional precipitation. This rain <br />shadow is a result of downslope flow in the winter storms that affect this area. Figure 3 <br />dramatically exhibits this feature from the coastal mountains in Central and Southern California <br />that are wet, to the San Joaquin and Imperial Valleys which are dry. The ratios of 1.5 observed <br />along the crestline of the Santa Ynez Mountains are, however, significant in terms of amounts of <br />rainfall since this area receives higher natural precipitation during winter storms due to <br />"upslope" flow. This upslope (orographic) flow results in mountainous areas of the west <br />receiving more precipitation than adjoining valleys (especially downwind valleys). Those <br />evaluating the Santa Barbara II randomized program concluded that convective band <br />precipitation was increased over a large area using this ground-based seeding approach <br />(Thompson et al. 1975). The increases in seeded convective bands in the Santa Barbara II <br />research program (Brown et al. 1974) were attributed to both static and dynamic effects. <br />Weather Damage ModiIicatiOD Program 7 <br />