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I I I I 3 Althouqh four attempts were made to 11:rack silver and ind,ium from the AqI and In203 ground releases upwind of Hlu.o into the HALO si te, there were no successes at doinq this. I I I I I I I I I I I I I I I The fixed tarqet experiments were sOIftewhat more successful with several experiments producinq positive tarqetinq results. In particular the two case studies for 14-15 March 1984 and 4 March 1985 qave exc:ellent results on tarqetinq both at HALO and at il downwind site. Because a sub- stantial number of the SCPP experiments used dry-ice seedinq, it wa,s not possible to use chemical targeting techniques. The isotopic analysis work yielded ~!ry valuable information i.n both winter seasons. In particular the climatology of 0 018 values for llOth 1985 and 1986 show peaks in the distributions .!lround -lOoC or -lloC at Kinqvale with colder temperature values for ice growth occurrinq down~'ind of: the Sierra Nevada crest. These results are interpreted to mean that !Inowfall downwind of the crest is composed of a hil:Jher proportion of ice pa.!:ticles originating at higher altitudes than at King'Vale, and that Wiry prc)bably there is less lower level supercooled water in the clouds fot' accrEttional growth by falling ice particles on the downwind side of the crest. Section III. Ground-Sased Precipitation Microphysics ProqJ:~aa Photomicrographs and sensitive mass balance techniques were used to study the growth mechanisms occurring in the winter storms over thl! Central Sierra Nevada. After some initial equipment difficulties in the hclrsh mountainous environment, this program produced a number of significant achievements. New equipment was developed, tested and used i.n the proqram. These included a microbalance for measuring masses of individual ice cry- stals and a snow crystal separator which segreqates snow particles into several bulk samples dependinq upon their masses. The characteristics of the fallinq snow crystals were rElcordeci every four minutes during the storms and this information was available :Eor com- parison with the stable isotope data described in Section II.. The masses of crystals were obtained by meltinq and measurement of the indiv'iciual melted drop diameters. By plotting the temperature of origin of the ice crystals (based on habit) against the masses of the crystals, it was pos- sible to form estimates of the contributions of "cold" habit and "warm" habit crystals to the snowfall and also the importance of the accretional growth processes to the precipitation occurrinq in this regicm. This type of information was investigated as a function of time throughout the storm. This, in turn, provides knowledge on changes in precipitation charclcteris- tics as functions of the mesoscale flow over the mountainous terrain.