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JULY 1988 RAUBER ET AL. 821 o to 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 ~ ~ 50 40 30 L I. "" 20 :z: 10 (f) 0 I.. ./ X I <l: -10 :: -20 -30 -40 -50 I / ;'i" ~ uJt / 55 ~ / ~ ~ 44 i::t 3 ., 3 I ------ ~ ~ ~ ~ H N --r.; ~ 1 (, 100/ 4 ~~ Hi !:) --- v. '\ \ I /1'-...... ~ "'f ~ ( ~ , ~ D ~~ I I ..-/ ( '7 I ) I 7 \ I L ...-r-'-r '--- ------- ----- X (I / -------- "'---- "-J 7\ / S50 V 50 40 30 20 10 o -10 -20 -30 -40 -50 -600 10 20 3D 40 50 60 70 80 90 100 110 120 130 140 150 160-60 (X AXIS IN KM) FiG. 7. Calculated seedline and fallout area of crystals for an aircraft flare release at 4000 m into a cloud with average L WC = 0.10 g m -3 on 5 February 1986 at 1800 UTe. The numbers 1-6 represent particles that originated at 200 m elevation intervals at the top (I) through bottom (6) of the I km deep curtain produced by the dropping flares. Each number appears five times representing the fallout location of particles originating at the same location, but falling with different fall velocities (see Eq. 7). .. of AgINH4I were incorporated into the targeting cal- culations. The assumption was made that nucleation would continue downwind of the release point with half of all nucleation events occurring within the initial 5 min. The SLCP was calculated so that crystals nu- cleated within the first 5 JIlin after release fell upwind of the target and crystals nucleated later fell downwind. The calculation of the SLCP proceeded exactly as de- scribed in subsection 3c(2), except that a 5 min delay time prior to nucleation of the target crystal was al- lowed. The fallout area was predicted by calculating the fallout trajectories of groups of crystals nucleating 0,5, 10, 15 and 20 min downwind of the seedline. The same fallspeed parameterization described in subsec- tion 3c(2) was used for crystals within each group. This scheme appeared adequate based on preliminary ob- servations of seeding effects as reported by Deshler and Reynolds (1987). 4. Evaluation studies An important emphasis of SCPP research was to evaluate the utility ofthe targeting scheme in operations by comparing the calculations with field measurements. In this section, three studies are presented which com- pare I) the diagnosed wind fields (u and v) with aircraft measurements; 2) predicted ice particle growth rates and habits with those measured by aircraft in seeded cloud regions; and 3) radar echo evolution within seeded cloud regions with predicted particle trajectories. a. Comparison of calculated and measured winds Comparisons of calculated wind fields with those measured by aircraft were made for seven fixed target experiments during the 1985/86 winter season. The comparison was limited to the region of the atmosphere bounded by the aircraft flight (primarily within region A of Fig. 3). In each case, soundings that would have been used operationally were used to initialize the tar- geting model. The aircraft flight pattern was the same in each case. After performing a climbout sounding over the valley, the aircraft proceeded eastward, de- scending from 5000 to 4000 m. The aircraft crossed the crestline, then reversed course and proceeded west- ward, descending along the MOCA toward the valley. The fillalleg consised of a climb over the foothills to the seeding altitude. This pattern completely encircled and penetrated the region of the cloud system influ- enced by seeding. The measured u and v wind com- ponents along this track were analyzed and graphically subtracted from calculated u- and v-component wind fields. Huggins et al. (1986) describe each comparison study in detail. Examples are presented here which demonstrate the important results. Figures 8a-c show calculated (solid) and measured (dashed) u- and v-components of the wind during two fixed target experiments. The error fields, determined by graphical subtraction, are shown in Figs. 8d-f. Fig- ures 8a, and d demonstrate important characteristics of the calculated u-component fields. In nearly all ex-